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Homogeneous CatalysisHomogeneous CatalysisNIOK
SchuitSchuit Institute of Catalysis Institute of Catalysis
D. Vogt NIOK CAIA course 2009 Homogeneous CatalysisTUTU//ee NIOKNIOK Intro_01
SchiermonnikoogSchiermonnikoogNovember 30 November 30 –– December 4, 2009December 4, 2009
Homogeneous CatalysisHomogeneous CatalysisOverviewOverview•• IntroductionIntroduction
History, general principles & aspectsHistory, general principles & aspects•• OrganometallicsOrganometallics
•• Elementary Reaction StepsElementary Reaction Steps
•• Homogeneous Homogeneous Catalytic ProcessesCatalytic ProcessesHydrogenationHydrogenationHydroformylationHydroformylationCarbonylation of Methanol (Carbonylation of Methanol (Monsanto acetic acid & Monsanto acetic acid & acetic anhydride process)acetic anhydride process)
•• ConceptsConcepts
SchuitSchuit Institute of Catalysis Institute of Catalysis
D. Vogt NIOK CAIA course 2009 Homogeneous CatalysisTUTU//ee NIOKNIOK
HydrocyanationHydrocyanationWackerWacker--Hoechst OxidationHoechst OxidationOligomerizationOligomerizationMetathesisMetathesisPolymerizationPolymerization
2
CatalysisCatalysis•• ““A catalyst accelerates a chemical reaction without A catalyst accelerates a chemical reaction without
appearing in any of the products. An equilibrium is appearing in any of the products. An equilibrium is equilibrated faster, but the position of the equilibrium will equilibrated faster, but the position of the equilibrium will not be changed”not be changed”
•• Catalysis is of major socioCatalysis is of major socio--economic importance to our society. In economic importance to our society. In order to solve the future problems connected with limited order to solve the future problems connected with limited resources and energy, as well as environmental protection, there is resources and energy, as well as environmental protection, there is no way without efficient catalysis.no way without efficient catalysis.
not be changed”not be changed”
SchuitSchuit Institute of Catalysis Institute of Catalysis
D. Vogt NIOK CAIA course 2009 Homogeneous CatalysisTUTU//ee NIOKNIOK Catalysis_01
no way without efficient catalysis.no way without efficient catalysis.
•• Catalysis is a highly interdisciplinary discipline, bringing together Catalysis is a highly interdisciplinary discipline, bringing together top of the art fields of science and technology.top of the art fields of science and technology.
ΔG
Rate Acceleration by CatalysisRate Acceleration by Catalysis
AB
A+B
AB
A+B
ΔGcatΔGG
SchuitSchuit Institute of Catalysis Institute of Catalysis
D. Vogt NIOK CAIA course 2009 Homogeneous CatalysisTUTU//ee NIOKNIOK
catalyseduncatalysed
reaction coordinate
Hessen/Elsevier
3
Selectivity by CatalysisSelectivity by Catalysis
Reactions: DC A + B
ΔGdΔGc ~~ΔGc,cat ΔGd,cat>
dc
SchuitSchuit Institute of Catalysis Institute of Catalysis
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A+BC DDC A+B
catalyzednoncatalyzedHessen/Elsevier
A Catalytic CycleA Catalytic Cycle
S CatAB
S
A
S
B Cat A Cat A
S S
SchuitSchuit Institute of Catalysis Institute of Catalysis
D. Vogt NIOK CAIA course 2009 Homogeneous CatalysisTUTU//ee NIOKNIOK
BHessen/Elsevier
4
Free Energy Profile of a Catalytic CycleFree Energy Profile of a Catalytic Cycle
ΔG1 in the scheme
A+B ΔG3
ΔG2ΔG1 >> ΔG2 ΔG3,
first step israte determining
ΔGo
SchuitSchuit Institute of Catalysis Institute of Catalysis
D. Vogt NIOK CAIA course 2009 Homogeneous CatalysisTUTU//ee NIOKNIOK
AB
Hessen/Elsevier
The Catalytic CycleThe Catalytic Cycle
s bstrates bstratecatalystcatalyst--substratesubstrate
complexcomplex tt
transition statetransition stateactive catalystactive catalystcatalyst precursorcatalyst precursor
substratesubstrate complexcomplex reagentreagent
SchuitSchuit Institute of Catalysis Institute of Catalysis
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catalystcatalyst--productproductcomplexcomplexproductproduct
Asymm-sw11
5
CatalysisCatalysis
SchuitSchuit Institute of Catalysis Institute of Catalysis
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Substrates can be converted into high value Substrates can be converted into high value products by very small amounts of a catalystproducts by very small amounts of a catalyst
Asymm-sw9
Types of CatalysisTypes of Catalysis
Biocatalysis(enzymes)
HomogeneousCatalysis
HeterogeneousCatalysis
PPd
PhPh
PtPt
Pt
SiO2
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P OPh Ph
PtPt
Pt
2
Hessen/Elsevier
6
Types of Catalysis: CharacteristicsTypes of Catalysis: Characteristics
Biocatalysis(enzymes)
HomogeneousCatalysis
HeterogeneousCatalysis
Complex bio-molecules / organisms
Geneticmodification
Well-definedmolecular species
Easy to study andto modify
Active species onsolid support
Difficult to study andto modify specifically
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Fermentation-likeprocesses (but rangeof conditions expanding)
Difficult to handlein processes(e.g. cat-productseparation)
Convenient inmost processes
Hessen/Elsevier
Catalysts for Homogeneous CatalysisCatalysts for Homogeneous Catalysis
- Lewis Acids and Bases- Electrons- Bronsted Acids and Bases
- Main group metal compounds
- coordination/activation of substrate
(Organometallic) Transition-metal catalystsare able to combine several functions, e.g.:
- Transition metal compounds Main group metal compounds
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- spatial restriction of the reaction environment- facilitating reaction steps using metal orbitals- redox processes- bringing reagents together in the coordination sphere
Hessen/Elsevier
7
Catalysis With BrCatalysis With Brøønsted Acids & Basesnsted Acids & Basesan Examplean Example
HH
Methanolysis of propene oxide
O OMe
OHOMe
OH
HO
H
MeOH
H -H
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OH
OMeMeOH MeObase O
OMeMeOH
O
Hessen/Elsevier
Catalytic Cycle and Elementary StepsCatalytic Cycle and Elementary Steps
- LLn-1M
HH
YY 18 16 18 16
oxidative additionoxidative addition
++ HHYY
Ln-2MHH
YY
RHH
-- LLMMLLnn MMLLnn--11
dissociationdissociation
ν = 18, 16ν = 18, 16 ν = 16, 14ν = 16, 14
ν = 18, 16ν = 18, 16
ν = 16, 14ν = 16, 14
dissociationdissociation
associationassociationν = 18, 16ν = 18, 16reductive eliminationreductive elimination
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+ L RLn-2M
YY
HH
RYY
HH
ν = 16, 14ν = 16, 14
insertioninsertionassociationassociation
ν = 18, 16ν = 18, 16
Catgen_sw1
8
Transition metalTransition metal
Factors Controlling Activity and SelectivityFactors Controlling Activity and Selectivityin a Metal Complexin a Metal Complex
R
•• e--configuration (d0-d10)•• orbital symmetry•• number of coordination sites•• ion or atom radius•• ionic or neutral•• nature of counter ions
LigandsLigands•• donor / acceptor properties•• dissociation constant•• space filling (cone angle)•• chelate effect•• bite angle•• symmetry
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ML
L
R
Substrate & SolventSubstrate & Solvent•• in principle like ligands
Catgen_sw2last change: 090909
Homogeneous CatalysisHomogeneous CatalysisOverviewOverview•• IntroductionIntroduction
History, general principles & aspectsHistory, general principles & aspects•• OrganometallicsOrganometallics
•• Elementary Reaction StepsElementary Reaction Steps
•• Homogeneous Homogeneous Catalytic ProcessesCatalytic ProcessesHydrogenationHydrogenationHydroformylationHydroformylationCarbonylation of Methanol (Carbonylation of Methanol (Monsanto acetic acid & Monsanto acetic acid & acetic anhydride process)acetic anhydride process)
•• ConceptsConcepts
SchuitSchuit Institute of Catalysis Institute of Catalysis
D. Vogt NIOK CAIA course 2009 Homogeneous CatalysisTUTU//ee NIOKNIOK
HydrocyanationHydrocyanationWackerWacker--Hoechst OxidationHoechst OxidationOligomerizationOligomerizationMetathesisMetathesisPolymerizationPolymerization
9
Organometallic CompoundsOrganometallic Compounds
•• Organometallic compounds are compounds that containOrganometallic compounds are compounds that containat least one Mat least one M--C bondC bond
OClCli l li l lNi
C
C CC
OOO
FePt
Cl
Cl
Cltypical examplestypical examples
but notbut notNi
CN
CNNC
NC 2-
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•• Of Importance to reactivityOf Importance to reactivitypolarity of the Mpolarity of the M--C bondC bondnumber & nature of the valence orbitals and electronsnumber & nature of the valence orbitals and electrons
Types of MTypes of M--C Bonds in the Periodic TableC Bonds in the Periodic Table
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electron deficiency compoundselectron deficiency compoundsionic compoundsionic compoundsdd--metals, Mmetals, M--C C σσ--bonding and bonding and ππ--bondingbonding
covalent Mcovalent M--C C σσ--bonding bonding metalloidsmetalloidsnonnon--metalsmetals
Organomet_02
10
Organometallic CompoundsOrganometallic CompoundsHistoryHistory
Year Organomet. comp. Name Remarks1827 [Pt(C2H4)Cl3]K Zeisse’s salt 1. olefin. comp.1841 [Me2As]2O Bunsen Kakodyl oxide[ 2 ]2 y1850-1900 R2Zn Frankland valence theory1868 [Pt(CO)Cl2]2 Schützenberger 1. carbonyl complex1890 Ni(CO)4 Mond founder of ICI1900-20 RMgX Grignard, Barbier synthetic aplic. of OM
R4Si KippingR2Hg, R3As Schlenk
1909 (Me)3PtI Pope 1. trans. metal alkyl
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1919 Cr-arene compounds Heim1920 Et4Pb, R2Te Midgley industrial application1920-50 RNa, RK, RLi Ziegler, Gilman, Wittig basis of org. alkali chem.1928 M(CO)n Hieber systematic investigation1931 H2Fe(CO)4 Hieber
Organometallic CompoundsOrganometallic CompoundsHistoryHistory
Year Organomet. comp. Name Remarks1938 Roelen hydroformylation1951 Ferrocene Pauson, Kealy, Miller organo transition metal chem.95 e oce e auso , ea y, e o ga o t a s t o eta c e .1953 R3Al Ziegler polymerization, renaissance of main
group OM chem.1955 Cr(C6H6)2 Fischer1959 [(C3H5)PdCl]2 Smidt, Hafner allyl complexes
[(C4Me4)NiCl2] Criegee1961 (PPh3)2Ir(CO)Cl Vaska reversible O2 binding1963 Nobel Prize Ziegler, Natta ethene polymerization
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1964 (CO)5W=C(OMe)Me Fischer 1. carbene complex1965 (PPh3)3RhCl Wilkinson, Coffey homogeneous hydrogenation catalyst1970 Wilkinson steric blocking of b-elimination1973 Nobel Prize Wilkinson, FischerFrom then explosive development
11
MainMain--Group Organometallic CompoundsGroup Organometallic Compounds•• Electronegativity and ionElectronegativity and ion--charactercharacter
polarization of the metalpolarization of the metal--C bondC bond M — Cδδ++ δδ--
Percentage ion character after PaulingPercentage ion character after Pauling
% ionic = 1 – e1/4(ENA- ENB)2
HF 50 C-Cs 57HCl 20 C-Na 47
compound % ionic C-M bond % ion character
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HCl 20 C Na 47HBr 10 C-Li 43HI 5 C-Mg 34
C-Al 22C-Si 12C-As 6
considerably covalent bondingconsiderably covalent bonding
Structure ExamplesStructure ExamplesElectron deficiency compoundsElectron deficiency compounds
tetrameric [MeLi]tetrameric [MeLi]44 and [and [nnBuLi]BuLi]44
Ionic compoundsIonic compoundsPhPh33CC-- NaNa++
Covalent MCovalent M--C C σσ--bonding bonding MeMe44SiSi
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MM--C C σσ--bonding and bonding and ππ--bondingbonding
CrC C
COOO
12
Structure ExamplesStructure Examples•• Influence of the metal with the same organic group Influence of the metal with the same organic group RR
Na
1) M = Na, Si, Fe R = C5H5- (Cp-)
ionic-lattice
NaHSi
Si-C σ-bondingR3Si moves around the ring
Fe
Ferrocene, π-complex
2) M = K, MgX, Pd, Ni R = C3H5 (allyl)
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K
ionic
MgX (ROR)2
σ-bonding
Pd
Pd-C σ-bond+ π-contribution
Ni
π-allyl complex
Structure ExamplesStructure Examples•• Influence of the organic group Influence of the organic group RR with the same metalwith the same metal
[MeLi]4 tetramer e- deficiency compound
ionic
[Me2Be]x polymer e- deficiency compound
tBu Be monomer linear σ-bonds
Li
BeBeMe
MeBe
Me
Me
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Bu2Be monomer, linear σ-bonds
Be
13
•• general: the more polar the bond , the more reactivegeneral: the more polar the bond , the more reactive
•• As a rule of thumb for (As a rule of thumb for (AA) elements) elements
R-Mδ- δ+
periodicperiodic
Reactivity of Organometallic CompoundsReactivity of Organometallic Compounds
periodic periodic tabletable
((AA)) RR--Cs > RCs > R--Rb > RRb > R--K > RK > R--Na > RNa > R--LiLiRR22Ca > RCa > R22Mg > RMg > R22BeBe
((BB)) RR--Cu > RCu > R--Ag > RAg > R--AuAu
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RR22Zn > RZn > R22Cd > HgRCd > HgR22
For elements of group (For elements of group (BB) the rule inverts.) the rule inverts.The least reactive compound of (The least reactive compound of (AA) is still) is stillmore reactive than the most reactive of (more reactive than the most reactive of (BB))
RR--Li > RLi > R--CuCu
RR22Be > RBe > R22ZnZn
main-gr_organo 25
Main Group Organometallic CompoundsMain Group Organometallic CompoundsMetal valence orbitals: 1 x s and 3 x pMetal valence orbitals: 1 x s and 3 x p
Octet ruleOctet ruleNoble gas configuration with 8 valence electronsNoble gas configuration with 8 valence electrons
CH3
AlCH3 CH3
CH3
SiCH3CH3
CH3
CH3
As CH3CH3
:
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6 v.e. 8 v.e. 8 v.e. includinglone pair
Lewis acid Lewis base
Hessen/Elsevier
14
Transition Metal Organometallic CompoundsTransition Metal Organometallic CompoundsMetal valence orbitals: 5 x d, 1 x s, and 3 x pMetal valence orbitals: 5 x d, 1 x s, and 3 x p
1818--electron ruleelectron ruleNoble gas configuration with 18 valence electronsNoble gas configuration with 18 valence electrons
2 x C5H51 x FeFe
= 2 x 5 = 10 v.e.= 8 v.e.
18 v.e.
1 C H = 5 v e
saturated
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ZrCH3 CH3
CH3
1 x C5H5
3 x CH3
1 x Zr
= 5 v.e.
= 3 x 1 = 3 v.e.= 4 v.e.
12 v.e. Lewis acidicHessen/Elsevier
e- available hapticity Ligand Metal-ligand structure1 η1 H M-H1 η1 Cl, Br, I M-X1 η1 OH M-OH1 η1 CN M-C≡N1 η1 CH3, alkyl M-CH3, M-R2 η1 CO PR3 M C≡O M PR
Counting ElectronsCounting Electrons
•• Metal atoms and ligands are Metal atoms and ligands are treated as neutraltreated as neutral
2 η CO, PR3 M-C≡O, M-PR3
2 η1 NH3, H2O M-NH3, M-OH2
2 η1 alkylidene M=CR2
2 η2 alkene M
2 η1 =O, =S M=O, M=S3 η1 NO(linear) M-N≡O
3 η3 C3H5, allyl M
•• Count all valence eCount all valence e-- of the of the mmetal & all etal & all ee-- donated by the donated by the ligandsligands
•• Correct for charges of the Correct for charges of the complexcomplex
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3 η1 alkylidyne M≡C-R
4 η4 1,3-diene, C4H6
M
5 η5 cyclopentadienyl,C5H5 M
6 η6 arene, C6H6
M
15
ClMn(CO)5 MnMn 7 e7 e--
ClCl 1 e1 e--
5 CO5 CO 10 e10 e-- =>=> 18 e18 e--
Cp2Fe (ferrocene) FeFe 8 e8 e--
Counting ElectronsCounting ElectronsExamplesClMn(CO)5 MnMn 7 e7 e--
ClCl 1 e1 e--
5 CO5 CO 10 e10 e-- =>=> 18 e18 e--
Cp2Fe (ferrocene) FeFe 8 e8 e--
2 Cp2 Cp 10 e10 e-- =>=> 18 e18 e--
CpRe(CO)3 ReRe 7 e7 e--
3 CO3 CO 6 e6 e--
CpCp 5 e5 e-- =>=> 18 e18 e--
Cr(CO)6 CrCr 6 e6 e--
6 CO6 CO 12 e12 e-- =>=> 18 e18 e--
Fe(CO)5 FeFe 8 e8 e--
2 Cp2 Cp 10 e10 e-- =>=> 18 e18 e--
CpRe(CO)3 ReRe 7 e7 e--
3 CO3 CO 6 e6 e--
CpCp 5 e5 e-- =>=> 18 e18 e--
Cr(CO)6 CrCr 6 e6 e--
6 CO6 CO 12 e12 e-- =>=> 18 e18 e--
Fe(CO)5 FeFe 8 e8 e--
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Co2(CO)8 CoCo 9 e9 e--
4 CO4 CO 8 e8 e--
CoCo--CoCo 1 e1 e-- =>=> 18 e18 e--
5 CO5 CO 10 e10 e-- =>=> 18 e18 e--
Ni(CO)4 NiNi 10 e10 e--
4 CO4 CO 8 e8 e-- =>=> 18 e18 e--
Co2(CO)8 CoCo 9 e9 e--
4 CO4 CO 8 e8 e--
CoCo--CoCo 1 e1 e-- =>=> 18 e18 e--
5 CO5 CO 10 e10 e-- =>=> 18 e18 e--
Ni(CO)4 NiNi 10 e10 e--
4 CO4 CO 8 e8 e-- =>=> 18 e18 e--
Organomet_06
Organometallic CompoundsOrganometallic Compounds18 Electron Rule18 Electron Rule
•• The 18The 18--electron rule recognizes the special stability of electron rule recognizes the special stability of ee----
configurations corresponding to the noble gas at the end of the configurations corresponding to the noble gas at the end of the corresponding long periodcorresponding long periodcorresponding long period.corresponding long period.
•• There are many exceptions to the 18There are many exceptions to the 18--electron rule which will be electron rule which will be explained by MOexplained by MO--theoretical considerations.theoretical considerations.
16.3 Scope of the 16/18-electron rule for d-block organometallic compounds
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Usually less than 18 e- Usually 18 e- 16 or 18 e-
Sc Ti V Cr Mn Fe Co NiY Zr Nb Mo Tc Ru Rh PdLa Hf Ta W Re Os Ir Pt
16
18 Electron Rule18 Electron RuleOctahedral Complex Including Octahedral Complex Including ππ--BondingBonding
4p
t1u*
T1ut2g* (π*)
T2
•• Strong Strong ππ--bonding bonding interaction with COinteraction with CO
Eg
T1u
Eg
t2g (π)
3d
4s
4pa1g*
eg*
T2g
T2g
A1g
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A1g1u
Cr(CO)6Cr 6 CO
t1u
eg
a1g
18 Electron Rule18 Electron RuleOctahedral Complex Cr(CO)Octahedral Complex Cr(CO)66
•• CO is a CO is a σσ--donor, raising the donor, raising the eegg orbitals in E and making them considerably orbitals in E and making them considerably antianti--bondingbonding..
•• CO is a strong CO is a strong ππ--acceptor, lowering the acceptor, lowering the tt2g2g orbitals in E and making them orbitals in E and making them bondingbonding..
Ligands that are both, strong Ligands that are both, strong σσ--donors and donors and ππ--acceptors are most efficient in acceptors are most efficient in forcing adherence to the 18forcing adherence to the 18--electron ruleelectron rule..
Exception:Exception: [Zn(en)3]2+ is a 22 eis a 22 e-- complex!complex!
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ZnN
NN
NN
N en is a weaker en is a weaker σσ--donor than CO and hence donor than CO and hence eeggorbitals are not sufficiently antiorbitals are not sufficiently anti--bonding to bonding to cause destabilizationcause destabilization
=>=> 4 4 ee-- in in eegg orbitalsorbitals and stable!and stable!
17
Square Planar 16 Electron ComplexesSquare Planar 16 Electron Complexes
ddxx22--yy22 is strongly antiis strongly anti--bonding (pointing directly towards the 4 ligands)bonding (pointing directly towards the 4 ligands)
Very important class of complexes, especially in homogeneous catalysisVery important class of complexes, especially in homogeneous catalysis
•• Square planar 16 Square planar 16 ee-- complexes of group 9 and 10, particularly for heavier complexes of group 9 and 10, particularly for heavier elements elements Rh(I)Rh(I),, Ir(I)Ir(I),, Pd(II)Pd(II),, Pt(II)Pt(II)
IrCl
PPh3OC
Ph3P IrIr 9 e9 e--
ClCl 1 e1 e--
COCO 2 e2 e--
2 Ph3P 4 ee-- =>=> 16 e16 e--Vaska’s complexVaska’s complex
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RhCl
PPh3Ph3P
Ph3P
Wilkinson’s complexWilkinson’s complex
RhRh 9 e9 e--
ClCl 1 e1 e--
3 Ph3P 6 ee-- =>=> 16 e16 e--
Exceptions from the 18/16 Electron RuleExceptions from the 18/16 Electron Rule
•• Exceptions are common on the left side of the dExceptions are common on the left side of the d--blockblock
•• Steric and electronic factors are in competitionSteric and electronic factors are in competition
VC
CC
C
C
C
O
O
O
OO
OW
CH3
H3CH3C
CH3
CH3
CH3
17 e17 e-- 12 e12 e--
C C CO O O
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Cr
OCCO
PPh3
17 e17 e--
steric bulk of PPhsteric bulk of PPh3 3 prevents prevents coordination of add. ligandcoordination of add. ligand
Cr Cr
C
CC C
C
OOO
18 e18 e--
long Crlong Cr--Cr bondCr bond
18
Typical Coordination GeometriesTypical Coordination Geometries
tetrahedral trigonalbipyramidal
octahedral
squarepyramidal
squareplanar
bipyramidal
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geometry determined by electronic (crystal / ligand field)and steric (interligand repulsion) factors
geometric constraints (e.g multidentate or stericallydemanding ligands) can lead to significant distortions
••
••
Hessen/Elsevier
dd--Metal ComplexesMetal ComplexesSome Common Ligand FieldsSome Common Ligand Fields
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•• Splitting diagrams referred to a common barycenterSplitting diagrams referred to a common barycenter
•• Splitting with respect to Splitting with respect to ΔO
squaresquareplanarplanar
trigonaltrigonalbipyramidalbipyramidal
squaresquarepyramidalpyramidal
octahedraloctahedral pentagonalpentagonalbipyramidalbipyramidal
squaresquareantiprismaticantiprismatic
19
dd--Metal ComplexesMetal Complexesππ--Bonding, Donor & Acceptor LigandsBonding, Donor & Acceptor Ligands
metal ligands metal ligands
ππ--acceptor ligands increase acceptor ligands increase ΔO
g g
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ππ--donor ligands decrease donor ligands decrease ΔO
dd--Metal CarbonylsMetal Carbonyls
•• Homoleptic carbonyl complexes M(CO)Homoleptic carbonyl complexes M(CO)nn exist of most of the dexist of most of the d--metalsmetals
Simple carbonyls of Pd and Pt are unstable and exist only at low TSimple carbonyls of Pd and Pt are unstable and exist only at low TSimple carbonyls of Pd and Pt are unstable and exist only at low TSimple carbonyls of Pd and Pt are unstable and exist only at low T
No sNo simple carbonyls are known for Cu, Ag, Au and group 3 (Sc, Y, La)imple carbonyls are known for Cu, Ag, Au and group 3 (Sc, Y, La)
Carbonyl complexes are very important precursors for other Carbonyl complexes are very important precursors for other organometallic compoundsorganometallic compounds
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organometallic compoundsorganometallic compounds
Carbonyl complexes are used in organic synthesis and catalysisCarbonyl complexes are used in organic synthesis and catalysis
20
MO’s of Carbon MonoxideMO’s of Carbon Monoxide
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•• HOMO has HOMO has σσ symmetrysymmetry and point away from C in the COand point away from C in the CO--axisaxis=>=> forms forms σσ--donordonor bonds with the metalbonds with the metal
•• LUMO’s are LUMO’s are ππ* orbitals which play a crucial role in overlap with t* orbitals which play a crucial role in overlap with t2g2g metal metal orbitalsorbitals=>=> CO acts as CO acts as strong strong ππ--acceptoracceptor
MO’s of Carbon MonoxideMO’s of Carbon Monoxide
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21
MO’s of Carbonyl ComplexesMO’s of Carbonyl ComplexesBond CharacteristicsBond Characteristics
emptyemptyoccupiedoccupied emptyempty
σσ--donordonor ππ--acceptoracceptor
occupiedoccupied
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pp
Types of CO Binding ModesTypes of CO Binding Modes
C
OC
O
O
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σσ--donordonor
M M
ππ--acceptoracceptor
M MM M
C
22
Types of CO Binding ModesTypes of CO Binding Modes
compound ν CO / cm -1Influence of Influence of
•• Electron poor metal center = competing Electron poor metal center = competing ππ--acceptor ligandsacceptor ligands=>=> reduced bond reduced bond length (stronger Clength (stronger C≡≡O) = higher O) = higher νCO
•• Electron rich metal center = strong Electron rich metal center = strong σσ--donor ligandsdonor ligands=>=> increased bond increased bond length (weaker Clength (weaker C≡≡O) = decreased O) = decreased νCO
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CO (g) 2143[M n(CO)6]+ 2090Cr(CO)6 2000[V(CO)6]- 1860[Ti(CO )6]2- 1750Fe2(CO )9 2082, 2019, 1829
coordination and coordination and charge on charge on νCO
Fe
C
CC
Fe
C
CC
C
C
CO
O
OOO
O
O
O
O
Related Related ππ--Acceptor LigandsAcceptor Ligands
C N- < N N < C NR < C O < C S < N O+
•• Ligands isoelectronic with CO sorted by increasing Ligands isoelectronic with CO sorted by increasing ππ--acceptor strengthacceptor strength
νCO can be used to determine ππ--acceptor strengthacceptor strength
i d d h CO t tt-- νCO is decreased when CO acts as a ππ--acceptoracceptor
-- other other ππ--acceptor ligands cause acceptor ligands cause νCO to increase
- donor ligands cause νCO to decreased
•• CNCN-- and NOand NO++ significantly differ from COsignificantly differ from CO
-- CNCN-- is a good is a good σσ--donor and a weak donor and a weak ππ--acceptoracceptor
-- NONO++ is very strongly eis very strongly e-- withdrawingwithdrawing
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-- NONO is very strongly eis very strongly e withdrawingwithdrawing
linear coordination,linear coordination,neutral 3 eneutral 3 e-- ligand ligand
bent coordination,bent coordination,as NOas NO--, 1 e, 1 e-- ligand ligand
23
Related Related ππ--Acceptor LigandsAcceptor Ligands•• The other ligands in the series NThe other ligands in the series N22, NCR, and CS preferably form complexes , NCR, and CS preferably form complexes
with metals in low oxidation stateswith metals in low oxidation states
•• SOSO22 is a fairly strong is a fairly strong ππ--acceptoracceptor
σσ--donor, donor, ππ--acceptor ligandacceptor ligand σσ--donation to the SOdonation to the SO22 ligandligandfound with found with ee-- rich metal centers, rich metal centers, SOSO22 acts as Lewis acid acts as Lewis acid
PFPF h blh bl t h t t COt h t t CO
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•• PFPF33 has comparable has comparable ππ--acceptor character to COacceptor character to CO
•• P(OR)P(OR)33 ligands are somewhat weaker ligands are somewhat weaker ππ--acceptors, while PHacceptors, while PH33 and alkyl phosphines and alkyl phosphines are stronger are stronger σσ--donorsdonors
Transition Metal AlkylsTransition Metal Alkyls
σ-interactionpolar M-Cbond
M Cδ-δ+
H H
Electron-deficienttransition-metal alkyls: agostic interactions
bond
H HH H H H
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CH
H
H
non-agosticα-agosticβ-agostic
M CC
H
H
H
HM
CC
H
HH
MC
C
H
H
H
Hessen/Elsevier
24
Carbenes and Metal AlkylidenesCarbenes and Metal AlkylidenesC
RNR2M
R singlettriplet
M CRR
NR2
R
R
NR
ggroundstate
tripletgroundstate
R
R
R
R
NR2
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carbene
nucleophilic vs electrophilic
R
R
R
R
R
NR2
NR2
R
Hessen/Elsevier
Fischer carbenesFischer carbenes
πM C σM
•• singlet ground state singlet ground state ((HeteroatomsHeteroatoms))
•• Late(r) transition metals Late(r) transition metals with lower oxidation stateswith lower oxidation states(donation of electrons)(donation of electrons)
σ
π
σ
M
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( )( )–– carbene is considered neutralcarbene is considered neutral
25
Schrock Carbenes (Alkylidenes)Schrock Carbenes (Alkylidenes)
•• ”Conventional" M=C bond:”Conventional" M=C bond:–– both both σσ en en ππ are covalent,are covalent,
expected polarization Mexpected polarization Md+d+--CCdd--
•• Triplet ground stateTriplet ground state
M σ
•• Triplet ground stateTriplet ground state•• Early transition metals with Early transition metals with
high oxidation stateshigh oxidation states–– Carbene is formally CCarbene is formally C22--
•• Carbene C is nucleophilicCarbene C is nucleophilic
πM
NMe2
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Ta
NMe2
Cl
ClC
H
t-Bu
H2O CH
t-BuH
H
Metal Alkylidene BondsMetal Alkylidene Bonds•• electrophilic Fischer carbenes react with a nucleophileselectrophilic Fischer carbenes react with a nucleophiles
(CO)5Cr COMe
Ph+ :NHR2 (CO)5Cr C
NR2
Ph(CO)5Cr C
OMe
Ph
NHR2 + MeOH
Schrock Carbenes
•• Early transition metal carbenesEarly transition metal carbenes•• filled carbon pfilled carbon pzz orbital lower inorbital lower in
energy than denergy than d--ππ orbitalsorbitals=>=> Schrock carbene C is nucleophilicSchrock carbene C is nucleophilic
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•• Schrock carbenes are catalysts for the alkene metathesis reactionSchrock carbenes are catalysts for the alkene metathesis reaction
TaClCl
CC
H+ Ta
ClClCCH
CH2
CMe3
H2
TaClCl
CH2 +H
26
Bonding SituationBonding SituationDewarDewar--ChattChatt--Duncanson ModelDuncanson Model
Transition Metal Transition Metal -- Alkene ComplexesAlkene Complexes
MC
CM
C
C
σσ--bondbond ππ--backbondbackbond
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emptyemptydd--orbitalorbital
filled filled ethylene ethylene ππ--orbitalorbital
filled filled dd--orbitalorbital
empty empty ethylene ethylene ππ* orbital* orbital
Metal Alkene BondsMetal Alkene BondsDewarDewar--ChattChatt--Duncanson ModelDuncanson Model
•• Donation of eDonation of e-- density from a filled density from a filled ππ--MOMOof the alkene into a vacant metal of the alkene into a vacant metal σσ--orbital.orbital.
•• Acceptance of eAcceptance of e-- density from a filled density from a filled
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pp yymetal dmetal dππ orbital into the vacant orbital into the vacant ππ**--MO MO of the alkene.of the alkene.
Organomet_52
27
Metal Alkene BondsMetal Alkene BondsBonding ModesBonding Modes
•• Depending on the electron density in both, the metal and the alkene, the Depending on the electron density in both, the metal and the alkene, the actual situation will lie between two extremesactual situation will lie between two extremes
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-- very every e-- rich metal fragmentsrich metal fragments-- strongly estrongly e-- withdrawing withdrawing
substituents on the alkenesubstituents on the alkene
-- normal situation for most alkenesnormal situation for most alkenes
Metal Alkene BondsMetal Alkene BondsBonding ModesBonding Modes
•• The conformation with respect to the metalThe conformation with respect to the metal--alkene bond depends on the alkene bond depends on the metal fragmentmetal fragment
ML
L
coordination no.: 3coordination no.: 316 valence e16 valence e--
LL22M(alkene)M(alkene)
ML
LL
coordination no.: 4coordination no.: 416 valence e16 valence e--
LL33M(alkene)M(alkene)
L
M
L
LL
coordination no.: 5coordination no.: 518 valence e18 valence e--
LL44M(alkene)M(alkene)
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•• ExamplesExamples(PPh(PPh33))22Ni(CNi(C22HH44)) K[PtCl K[PtCl 33(C(C22HH44)])] (PPh(PPh33))22IrBr(CO)TCNEIrBr(CO)TCNEPt(CPt(C22HH44))33 TCNE = tetracyanoetheneTCNE = tetracyanoethene
28
Metal Allyl BondsMetal Allyl BondsBonding ModesBonding Modes
Fe
OCOC
HH
HH
Pd ClCl
Pd NiL
X
HH
ηη11-- coordinationcoordination ηη33-- coordinationcoordination ηη11-- ηη22-- coordinationcoordination
3 H3H3
•• SynSyn and and antianti protons can be distinguished in protons can be distinguished in 11HH--NMR spectrumNMR spectrum•• Dynamic behavior (isomerization) on the NMR timeDynamic behavior (isomerization) on the NMR time--scale often leads to scale often leads to
averaged signalsaveraged signals
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M
H
H
H3
HH
H2
H1
H2
H1
MH1
H2
H1
H2
Mantianti
synsyn
antianti
synsyn
•• Allyl metal complexes are important intermediates and metalAllyl metal complexes are important intermediates and metal--precursors precursors in catalytic reactionsin catalytic reactions
Metal Allyl BindingMetal Allyl Binding
ligandligandAA
σσ--bondsbonds ππ--bondsbonds
BB
ss ppyyppxx
ψψ11 ψψ22 ψψ33AA22
metalmetal
BB11
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ddzz22
ppzz
ddyzyzddxzxz
see also extra information H16_7 allyl_radicalsee also extra information H16_7 allyl_radical
29
Metal Allyl BondsMetal Allyl BondsSynthesisSynthesis
Fe
OC COCO
HClFe Cl
OC CO
•• protonation of 1,3protonation of 1,3--diene complexesdiene complexes
OC CO OC CO
MgBr2 + NiCl2 Ni + 2 MgBrCl
•• reaction of metal halides with an allylreaction of metal halides with an allyl--Grignard reagentGrignard reagent
X + Pd(PPh3)4 PdX(PPh3)2
•• allylic substitution reactionsallylic substitution reactions
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PdX(PPh3)2
X = OAc, OCORO
HCo(CO)4 +- CO
+Co(CO)3Co(CO)3
•• reaction of a metalreaction of a metal--hydride with a 1,3hydride with a 1,3--dienediene
Pd ClCl
PdDMSO
PdDMSOCl
DMSO2
Dynamic NMR BehaviorDynamic NMR Behavior
11H NMR spectrum of [(allyl)PdCl]H NMR spectrum of [(allyl)PdCl]22(d(d66 DMSO 140DMSO 140°°C 200 MHz)C 200 MHz)
11H NMR spectrum of [(allyl)PdCl]H NMR spectrum of [(allyl)PdCl]22(CDCl(CDCl33, 25, 25°°C, 200 MHz)C, 200 MHz)
(d(d66--DMSO, 140DMSO, 140 C, 200 MHz)C, 200 MHz)
HH1,21,2
•• A4X patternHH11HH22
HH33
H1
H2
H3
H1
H2
M
•• typical A2M2X pattern ofη3- bound allyl ligand
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5.8 5.4 5.0 4.6 4.2 3.8 3.4 5.8 5.4 5.0 4.6 4.2 3.8 3.4 3.0 ppm3.0 ppm
HH33
5.8 5.4 5.0 4.6 4.2 3.8 3.4 5.8 5.4 5.0 4.6 4.2 3.8 3.4 3.0 ppm3.0 ppm
30
Homogeneous CatalysisHomogeneous CatalysisOverviewOverview•• IntroductionIntroduction
History, general principles & aspectsHistory, general principles & aspects•• OrganometallicsOrganometallics
•• Elementary Reaction StepsElementary Reaction Steps
•• Homogeneous Homogeneous Catalytic ProcessesCatalytic ProcessesHydrogenationHydrogenationHydroformylationHydroformylationCarbonylation of Methanol (Carbonylation of Methanol (Monsanto acetic acid & Monsanto acetic acid & acetic anhydride process)acetic anhydride process)
•• ConceptsConcepts
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HydrocyanationHydrocyanationWackerWacker--Hoechst OxidationHoechst OxidationOligomerizationOligomerizationMetathesisMetathesisPolymerizationPolymerization
Catalytic Cycle and Elementary StepsCatalytic Cycle and Elementary Steps
LLn-1M
HH
YYoxidative additionoxidative addition
++ HHYY- L
Ln-2MHH
YY
R
-- LL
YY
MMLLnn MMLLnn--11
dissociationdissociation
ν = 18, 16ν = 18, 16 ν = 16, 14ν = 16, 14
ν = 18, 16ν = 18, 16
ν = 16, 14ν = 16, 14
dissociationdissociation
associationassociationν 18 16ν 18 16
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+ L RLn-2M
YY
RHH
RYY
HH
ν = 16, 14ν = 16, 14
ν = 18, 16ν = 18, 16reductive eliminationreductive elimination
insertioninsertionassociationassociation
ν = 18, 16ν = 18, 16
Catgen_sw1
31
Transition metalTransition metal
Factors Controlling Activity and SelectivityFactors Controlling Activity and Selectivityin a Metal Complexin a Metal Complex
R
•• e--configuration (d0-d10)•• orbital symmetry•• number of coordination sites•• ion or atom radius•• ionic or neutral•• nature of counter ions
LigandsLigands•• donor / acceptor properties•• dissociation constant•• space filling (cone angle)•• chelate effect•• bite angle•• symmetry
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ML
L
R
SubstrateSubstrate•• in principle like ligands
Catgen_sw2
R3
Tolman’s Cone AngleTolman’s Cone AngleSteric Effects of Monodentate LigandsSteric Effects of Monodentate Ligands
°2.28 A Θ1/2Θ = Σ Θi / 2
3
2/3
P
R1 R2
Chadwick A. Tolman
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C. A. Tolman, Chem. Rev. 1977, 77, 313-348.
React_mech_37
•• Steric crowding favors dissociative activation because in this way the Steric crowding favors dissociative activation because in this way the formation of the activated complex can relief strain.formation of the activated complex can relief strain.
Θ = Σ Θi / 2i=1
2/3
metal atommetal atom
last change: 090909
32
Tolman’s Cone AngleTolman’s Cone AngleChelating LigandsChelating Ligands
β
Θ
metal atommetal atom
P
R2
R1 R1
R2
P
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C. A. Tolman, W. C. Seidel, L. W. Gosser, J. Am. Chem. Soc. 1974, 96, 53-60.
metal atommetal atom
Catgen_sw63
Ligand Θ / ° Ligand Θ / °CH3 90 P(OiPr)3 130
Tolman’s Cone AngleTolman’s Cone AngleMonodentate LigandsMonodentate Ligands
CO 95 η5-C5H5 (Cp) 136Cl, Et 102 PEt3 137PF3 104 P(OoTol)3 141Br, Ph 105 PPh3 145I, P(OCH3)3 107 P(iPr)3 160P(CH3)3 118 C5(CH3)5 (Cp*) 165tBu 126 PCy3 170
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Bu 126 PCy3 170P(OPh)3 128 P(tBu)3 182
React_mech_38
C. A. Tolman, Chem. Rev. 1977, 77, 313-348.L. Stahl, R. D. Ernst, J. Am. Chem. Soc. 1987, 109, 5673.
•• Substitution reactions are commonly dominated by Substitution reactions are commonly dominated by steric effectssteric effects ((ΘΘ) and not ) and not by by electronic effectselectronic effects ((pKpKaa).).
33
Ligand Steric InfluenceLigand Steric Influence•• Steric bulk increases the rate of dissociative processes.Steric bulk increases the rate of dissociative processes.
NiL4 NiL3 + L
Cone angle Cone angle ΘΘ and Kand KDD for some Ni complexesfor some Ni complexes
C. A. Tolman, Chem. Rev. 1977, 77, 313-348.
L Θ /° KD
PMe3 118 < 10-9
PEt3 132 1.2x10-5
PMePh2 137 5.0x10-2
PPh3 145 largePtBu3 182 largein benzene at 25°C
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In extreme cases even unusual electron configurations can be stabilized.In extreme cases even unusual electron configurations can be stabilized.
NiL4 NiL3 + L NiL2 + 2 Lνν = 16 e= 16 e--νν = 18 e= 18 e-- νν = 14 e= 14 e--
Cy3P Ni PCy3e.g.e.g.
Tolman’s Cone AngleTolman’s Cone AngleProblemsProblems
•• different conformations of substituentsdifferent conformations of substituents
°2.28 A
•• very bulky ligandsvery bulky ligands
•• local space at the metallocal space at the metal
•• chelating ligandschelating ligands•• flexibility
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tan α = h / dΘ = 180 + 2 α
αh
d
Catgen_sw66
34
Ligand Electronic PropertiesLigand Electronic PropertiesTolman’s Tolman’s χχ--Value,Value,
νCO = 2056.1 + χi [cm-1]Σ3
i=1LNi(CO)3 {ν0 = P(tBu)3Ni(CO)3}TolmanTolman:: forfor
QUALE (Q tit ti A l i f Li d Eff t )QUALE (Q tit ti A l i f Li d Eff t )
group 1group 1:: σσ--donor ligandsdonor ligandsgroup 2group 2:: σσ--donor/ donor/ ππ--acceptoracceptor
QUALE (Quantitative Analysis of Ligand Effects)QUALE (Quantitative Analysis of Ligand Effects)
1940
1950
1960
group 2group 2ν CO
/cm
-1
GieringGiering::CpFe(COMe)(CO)L
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ligandsligands
A.L. Fernandez, C. Reyes, A. Prock, W.P. Giering,J. Chem. Soc., Perkin Trans. 2, 2000, 1033-1041.M.M. Rahman, H.-Y. Liu, K. Eriks, A. Prock, W.P. Giering, Organometallics, 8, 1-7.C. A. Tolman, Chem. Rev. 1977, 77, 313-348.
1910
1920
1930
0.1 0.2 0.3 0.4 0.5 0.6
group 1group 1
E0/V
Organomet_22
Dimerization of PropeneDimerization of Propene+ +
[Ni-Kat.]
headhead--headhead headhead--tailtail tailtail--tailtail
n-Hexenes80
90%
2,3-Dimethylbutene2-Methylpentene
NiR3P
+
AlCl4-Cat. :
T = - 20°C p = 1 bar30
40
50
60
70
80
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B. Bogdanovic, Adv. Organomet. Chem. 1979, 17, 105-140.
T 20 C , p 1 bar
PPh3 PMe3 PCy3iPr2PtBu-
0
10
20
- iPrPtBu2
Catgen_sw5
35
Dimerization of PropeneDimerization of PropeneTry to Explain Ligand Influences !Try to Explain Ligand Influences !
NiL
XH
CH3
H3C
NiNi--CC11 insertioninsertion
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B. Bogdanovic, Adv. Organomet. Chem. 1979, 17, 105-140.G. Henrici-Olivé, S. Olivé, Top. Curr. Chem. 1976, 67, 107-127
NiNi--CC22 insertioninsertion
solutionsolution
VCH
*
OligoOligo-- and Cyclooligomerization of 1,3and Cyclooligomerization of 1,3--ButadieneButadieneLigand InfluencesLigand Influences
[ L'''Ni/R2NH ] [ Ni ]
[ L''Ni ]
[ L'Ni ]
1,5-COD
[ L'Ni ]
DVCB
Günther Wilke
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P. Heimbach, P. W. Jolly, G. Wilke, Adv. Organomet. Chem. 1970, 8, 29.
1,3,6-OT ttt-1,5,9-CDT
L' = P(OCL' = P(OC66HH44--oo--Ph)Ph)3 , 3 , Θ = 152° ; L'' = P(Cy)L'' = P(Cy)3 , 3 , Θ = 170°; L''' = P(OEt)L''' = P(OEt)3 , 3 , Θ = 109°
Catgen_sw6
36
Mechanistic Routes to Different ProductsMechanistic Routes to Different ProductsTry to Explain Ligand Influences !Try to Explain Ligand Influences !
Ni[Ni] Ni Ni1,5-COD
VCH
*
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G. Wilke, Angew. Chem. 1988, 100, 189.
ttt-1,5,9-CDToxidoxid. coupling. coupling
elem. react. stepselem. react. steps
solutionsolution
Selectivity Control by L/NiSelectivity Control by L/Ni--RatioRatio
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L = PPhL = PPh33, T = 60, T = 60°°C, [Ni] = 32 mmol/lC, [Ni] = 32 mmol/l
P. Heimbach, H. Schenkluhn, Top. Curr. Chem. 1980, 92, 45.Catgen_sw7
37
Bulky LigandsBulky LigandsHeck Olefination ReactionHeck Olefination Reaction
OP
MeO
N
I+
[Pd(dba)2 / 2 L]
NEt3, CH3CN80°C, 45 min
PdL
Br
BrPd
L
catalystcatalystO
MeO
OP
O
A
Bonve
rsio
n [%
]on
vers
ion
[%]
40
60
80
100 TON up to 500.000TON up to 500.000
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O O
O OPPd
PPd
(o-tol)2
(o-tol)2
C
Catgen_sw17
coco
0
20
PPh3
P(o-
tol) 3
P(O
Ph) 3 A B C
G.P.F. van Strijdonck, M.D.K. Boele, P.C.J. Kamer, J.G. de Vries, P. W.N.M. van Leeuwen, Eur. J. Inorg. Chem. 1999, 1073-1076.
Bulky Ligands in Bulky Ligands in Heck Olefination ReactionHeck Olefination ReactionI
+[Pd(dba)2 / 2 L]
NEt3, CH3CN80°C, 45 min
P4a: L =4a: L = OP
MeO
N4b L4b LPd
L
Br
BrPd
L
P4a: L =4a: L = PO
MeO
N4b: L =4b: L = catalystcatalyst
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38
I+
[Pd(dba)2 / 2 L]
NEt3, CH3CN80°C, 45 min
Bulky Ligands in Bulky Ligands in Heck Olefination ReactionHeck Olefination Reaction
rate law:rate law: zero order in [iodobenzene]zero order in [iodobenzene] (0.10 (0.10 –– 2.0 M)2.0 M)zero order in [NEtzero order in [NEt33]] (0.16 (0.16 –– 2.5 M)2.5 M)first order in [alkene]first order in [alkene] ( 0 ( 0 –– 4.0 M)4.0 M)½ order in [Pd]½ order in [Pd] ( 0 ( 0 –– 4.0 mM)4.0 mM)
SchuitSchuit Institute of Catalysis Institute of Catalysis
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r = k[alkene][Pd]r = k[alkene][Pd]1/21/2
What does this mean ?What does this mean ?
Bulky LigandsBulky LigandsHeck Olefination ReactionHeck Olefination Reaction
[Pd-L] ArXB
HBX
catalyst resting statecatalyst resting state
PdX
XPd
L
Ar LAr
R
PdArLX
PdLX
H
Ar RPd
LX
Ar
H R
PdHLX
Ar
R
B
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•• bulky ligands suppress formation of binuclear complexesbulky ligands suppress formation of binuclear complexes•• oxidative addition is NOT rate limiting oxidative addition is NOT rate limiting !!
very high TONvery high TON
H R
G.P.F. van Strijdonck, M.D.K. Boele, P.C.J. Kamer, J.G. de Vries, P. W.N.M. van Leeuwen, Eur. J. Inorg. Chem. 1999, 1073-1076.
r = kr = k22 KK1/21/2[alkene][Pd][alkene][Pd]1/21/2
39
Copolymerization of Ethene and COCopolymerization of Ethene and COEffects of Chelating LigandEffects of Chelating Ligand(PPh3)2PdX2
CH3OH+ CO
O
O
methylpropionatemethylpropionate> 98 %> 98 %
CH3OH
(DPPP)2PdX2
+ CO
O
O
Hn
alternating polyketonealternating polyketone> 99.9 %> 99.9 %
PPh2
PPh2
X = F3CSO3- ; DPPP :
COP 1 InsertionO
PP
OCPd
P
R
PdP
ORP
Eite DrentEite Drent
SchuitSchuit Institute of Catalysis Institute of Catalysis
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E. Drent, J. A. M. van Broekhoven, P. H. M. Budzelaar in Appl. Homog. Catal. with Organomet. Comp.(Eds.: B. Cornils, W. A. Herrmann) Vol. 1, VCH 1996, pp. 333-351.
PPd CO
R
P 1. Insertion
2. C2H4 PPd RPR
PPd CO
R
P
PPd
ORP
Catgen_sw10
Natural Bite Angle Natural Bite Angle ββnn of a Chelating Ligandof a Chelating Ligand
PP
PP
ββnn
d d MM--PP
d d RhRh--PP = 2.315 A= 2.315 A
d d NiNi--PP = 2.177 A= 2.177 A
°°°°
SchuitSchuit Institute of Catalysis Institute of Catalysis
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“The natural bite angle (βn) is defined as the preferred chelation angle determined only by ligand backbone constraints and not by metal valence angles.
The flexibility range is defined as the accessible range of bite angles within less than 3 kcal / mol excess strain energy from the calculated bite angle”.C. P. Casey, G. T. Whiteker, Isr. J. Chem. 1990, 30, 299-304.
Catgen_sw78
40
Flexibility Range of Xantphos LigandsFlexibility Range of Xantphos Ligands
SixantphosSixantphos
l mol
l mol
--11)) DPEphosDPEphos
O O
Si
mat
iona
l ene
rgy
(kca
lm
atio
nal e
nerg
y (k
cal
DPEphos
P P P P
Sixantphos
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PP--RhRh--PP
ββnn = 108= 108°°
PP--RhRh--PP
ββnn = 101= 101°°
conf
orco
nfor
Catgen_sw79
Bite Angle Electronic EffectsBite Angle Electronic Effects
E [ e
V ]
E [ e
V ]
≈
πu
δg*
≈
2b1
4a1
2b2
PP
PPMM
δ δ
δg, πg
δg*
1b 1a
3a1
2a1, 2b2, 1a2
•• ββnn small =>small => nucleophilic character nucleophilic character
raised reduction potentialraised reduction potential
•• ββnn large =>large => electrophilic characterelectrophilic characterlower reduction potentiallower reduction potential
a large bite angle cana large bite angle can
SchuitSchuit Institute of Catalysis Institute of Catalysis
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S. Otsuka, J. Organomet. Chem. 1980, 200, 191.T. Yoshida, K. Tatsumi, S. Otsuka, Pure Appl. Chem. 1980, 52, 713.
z
x
y
LLPPttLL
x
zyPPtt
LL
LL
δu, δg 1b1, 1a1
Walsh diagram for d10 fragments
a large bite angle cana large bite angle can-- enhance the coordination of an olefinenhance the coordination of an olefin-- enhance reductive eliminationsenhance reductive eliminations
41
Bite Angle EffectsBite Angle EffectsRates of Reductive EliminationRates of Reductive Elimination
P
P
PPd
P
PPd
CN
TMSP P^P
NC CH TMS- NC-CH2TMS
100
1000
10000
log
k [s
-1]
91°
98°
•• acceleration by 104 !
SchuitSchuit Institute of Catalysis Institute of Catalysis
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J.E. Marcone, K.G. Moloy, J. Am. Chem. Soc. 1998, 120, 8527-8528.
1
10
dppe dppp diop
-
85°
Ligand Bite AnglesLigand Bite Angles
DPEphosDPEphosββnn = 102= 102°° (86(86--120120°°))
OPh2P PPh2
SixantphosSixantphosββnn = 109= 109°° (93(93--130)130)
OPh2P PPh2
Si
Ph2P PPh2
BISBIBISBIββnn = 123= 123°° (101(101--148148°°))
PPh2Ph2PTRANSphosTRANSphosββnn = 111.2= 111.2°° ββnn (( )) ββnn (( ))ββnn (( ))ββnn 111.2 111.2
ThixantphosThixantphosββnn = 110= 110°° (96(96--130130°°))
OPh2P PPh2
S
XantphosXantphosββnn = 111= 111°° (97(97--133133°°))
OPh2P PPh2
O O
Ph2P PPh2
DIOPDIOPββnn = 98= 98°° (90(90--120120°°))
BINAPBINAPββnn = 92= 92°°
Ph2P PPh2
BINAPOBINAPOββnn = 105= 105°°
O OPPh2Ph2P
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Ph2P PPh2DPPEDPPE
ββnn = 78= 78°°
OPPh2Ph2P
DBFphosDBFphosββnn = 131= 131°° (117(117--147)147)
DPPPDPPPββnn = 86= 86°°
Ph2P PPh2
DPPBDPPBββnn = 99= 99°°
Ph2P PPh2
P.W.M.N. van Leeuwen, P.C.J. Kamer, J.N.H. Reek, P. Dierkes, Chem. Rev. 2000, 100, 2741-2769.
42
Large Bite Angle DiphosphinesLarge Bite Angle Diphosphines
PP PPMM
rigid backbonerigid backbone
large bite anglelarge bite angle ββnn
O
X RR
PAr2PAr2
X R Ar βn** [°]
1a H, H H Ph 1051b SiMe2 H Ph 1121c S Me Ph 113
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Xantphos ligandsXantphos ligands
1
1d CMe2 H Ph 1141e CMe2 H 3,5-(CF3)2Ph 1171f - H Ph 140
* calculated based on Ni* calculated based on Ni--P = 2.177 AP = 2.177 A°°
Mirko Kranenburg, Organometallics 1995, 14, 3081-3089.
XX--Ray Structures of Xantphos LigandsRay Structures of Xantphos Ligands
OO PPPP
SiSi
OOPPPP
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W. Goertz, W. Keim, D. Vogt, U. Englert, Maarten D.K. Boele, L.A. van der Veen, P.C.J. Kamer, P.W.N.M. van Leeuwen, J. Chem. Soc., Dalton Trans. 1998, 2981-2988.
SixantphosSixantphosββnn = 109= 109°° (93(93--130)130)
SS
ThixantphosThixantphosββnn = 110= 110°° (96(96--130130°°))
43
Hydroformylation of 1Hydroformylation of 1--OcteneOctene
50
60109°
112° 123°
+ CO/H2 CHOCHO
+[Rh-cat.]
10
20
30
40
l/b
l/b --
ratio
ratio
84°
102°
108°
131°
Piet van Leeuwen
SchuitSchuit Institute of Catalysis Institute of Catalysis
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M. Kranenburg, Y.E.M. van der Burgt, P.C.J. Kamer, P.W.N.M. van Leeuwen, K. Goubitz, J. Fraanje, Organometallics, 1995, 14, 3081-3089.
0
DPP
E
DPE
phos
Sixa
nt
Thix
ant
Xant
phos
BIS
BI
DB
Fpho
sCatgen_sw14
T = 40°C, p = 10 bar CO/H2 (1:1), substrate/Rh = 674, L/Rh = 2.2, [Rh] = 1.78 mM
Counterion Effects and Hemilabile LigandsCounterion Effects and Hemilabile LigandsHydrovinylation of StyreneHydrovinylation of Styrene
+[(η3-allyl)NiBr]2 / L*
AgXCH2Cl2, - 45°C, 1.5 h
* + + homo-oligomers+ higher co-oligomers
nver
sion
[%]
nver
sion
[%]
40
60
80
100 AB
P
A
P
O
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M. Nandi, J. Jin, T. V. RajanBabu, J. Am. Chem. Soc., 1999, 121, 9899-9900.
con
con
0
20
40
OTf ClO4 NTf2 SbF6 B(ArF)4
P
B
Catgen_sw86
44
Simulated StructureSimulated StructureWeakly Coordinating Anion as Bulky LigandWeakly Coordinating Anion as Bulky Ligand
H
XOP
Ni
**
free volumefree volumearound Ni at 2.2 Åaround Ni at 2.2 Å
styrenestyrene
PP
NN
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Coordination of the olefin at the metal is supposed to be the enantioselective stepCoordination of the olefin at the metal is supposed to be the enantioselective step
HYVHYV--swsw8787
around Ni at 2.2 Åaround Ni at 2.2 Å
K. Angermund, A. Eckerle, F. Lutz, K. Angermund, A. Eckerle, F. Lutz, Z. Naturforsch. Z. Naturforsch. 19951995, , 50b50b, 488., 488.
Chirality in NatureChirality in Nature
Snail (Snail (Helix pomatiaHelix pomatia))
Appears as right and left handed form in a ratio of 5000 15000:1.
Colored snail (Colored snail (Liguus virgeneusLiguus virgeneus))
Like most snails right winding; only mutants occasionally have the opposite winding.
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Field bind weed (Field bind weed (Convolvulus arvensisConvolvulus arvensis))
As most climbing plants, it only grows right winding.
Asymm-sw3
45
Different Effect of EnantiomersDifferent Effect of Enantiomers
odor of lemonodor of lemon odor of orangesodor of oranges
LimoneneLimoneneS
CH3R
CH3
AsparagineAsparagine
bitter tastebitter taste
S H2N OHO
O
NH2
sweet tastesweet taste
RNH2
O
O
NH2
HO
odor of lemonodor of lemon odor of orangesodor of oranges
PropranololPropranololS
OOH
NH
CH3
CH3
R
OOH
NH
H3C
CH3
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betabeta--blockerblocker
S
causes liver damagecauses liver damage
R
EthambutolEthambutol
drug for tuberculosis treatmentdrug for tuberculosis treatment
S,SH3C
N
OH
N
OH
CH3
causes blindnesscauses blindness
R,RCH3
N
HO
N
HO
H3C
Asymm-sw5
Use of Chiral Compounds Use of Chiral Compounds •• Food additivesFood additives•• PharmaceuticalsPharmaceuticals•• Feed additivesFeed additives
The different physiological effect of enantiomers must The different physiological effect of enantiomers must be taken into account!be taken into account!
•• Feed additivesFeed additives•• Agro chemicalsAgro chemicals
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The "The "wrongwrong" enantiomer can be:" enantiomer can be:•• ineffective,ineffective,•• poisonouspoisonous•• of opposite effect.of opposite effect.
Asymm-sw6
46
•• The main markets for chiral technology and chiral The main markets for chiral technology and chiral intermediates are:intermediates are:
Chiral MoleculesChiral MoleculesMarket SegmentationMarket Segmentation
-- PharmaceuticalsPharmaceuticals (81 %)(81 %)
-- AgrochemicalsAgrochemicals (14 %)(14 %)
-- Flavors and fragrancesFlavors and fragrances (5 %)(5 %)
-- Material science, polymers, liquid crystals and veterinary medicinesMaterial science, polymers, liquid crystals and veterinary medicines
F & F Materials
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Source: Frost & Sullivan, 2001
5%Agro14%
0%
Pharma81%
Asymmetric SynthesisAsymmetric Synthesis•• classical synthesisclassical synthesis
+ +
reagentreagent product 1:1product 1:1substratesubstrate
•• stereoselective synthesisstereoselective synthesis
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chiral auxiliarychiral auxiliary
reagentreagent
+
substratesubstrate product, left handed onlyproduct, left handed only
Asymm-sw7
47
Conversion of a Substrate Using aConversion of a Substrate Using aChiral CatalystChiral Catalyst
H Hchiral
t l tH H
(Si)(Si)
CH3
((SS))
catalyst
chiral ligand
H+
((RR))
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A chiral catalystchiral catalyst favors one face of the substrateOneOne product enantiomerenantiomer is formed predominantlypredominantly
Asymm-sw13
Asymmetric SynthesisAsymmetric Synthesis
*
HH
*O OHHOHH
HH
sisi--half spacehalf spaceSSRR
rere--half spacehalf space
ΔΔ
G
[kJm
ol-1
]#
6
8
10
12
ΔG# ΔG#
ΔΔG#
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0
2
4
0 20 40 60 80 100ee [%]
ΔGR ΔGS
48
Homogeneous CatalysisHomogeneous CatalysisOverviewOverview•• IntroductionIntroduction
History, general principles & aspectsHistory, general principles & aspects•• OrganometallicsOrganometallics
•• Elementary Reaction StepsElementary Reaction Steps
•• Homogeneous Homogeneous Catalytic ProcessesCatalytic ProcessesHydrogenationHydrogenationHydroformylationHydroformylationCarbonylation of Methanol (Carbonylation of Methanol (Monsanto acetic acid & Monsanto acetic acid & acetic anhydride process)acetic anhydride process)
•• ConceptsConcepts
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HydrocyanationHydrocyanationWackerWacker--Hoechst OxidationHoechst OxidationOligomerizationOligomerizationMetathesisMetathesisPolymerizationPolymerization
heterogeneous homogeneous biocatalysis
Comparison of Catalytic PrinciplesComparison of Catalytic Principles
Advantages and disadvantages of heterogeneous, homogeneous, Advantages and disadvantages of heterogeneous, homogeneous, and bio catalysisand bio catalysis
heterogeneous homogeneous biocatalysisg g y
Conditions generally harsh mild mild
Activity changing high i.g. very high
Selectivity changing high i.g. very high
Catalyst life-time high changing i.g. low
Catalyst recycling solved expensive expensive
Sensitivity agains poisons high low high
Diffusion problems possible none only whole cells
g g y
Conditions generally harsh mild mild
Activity changing high i.g. very high
Selectivity changing high i.g. very high
Catalyst life-time high changing i.g. low
Catalyst recycling solved expensive expensive
Sensitivity agains poisons high low high
Diffusion problems possible none only whole cells
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Diffusion problems possible none only whole cells
Mechanistic understanding low medium to good medium
Catalysis_07
Diffusion problems possible none only whole cells
Mechanistic understanding low medium to good medium
49
Homogeneous CatalysisHomogeneous Catalysis
Process Catalyst Capacity / 1000 t/a
Homogeneous catalytic processes in industryHomogeneous catalytic processes in industry
Hydroformylation HRh(CO)n(PR3)m 3690
HCo(CO)n(PR3)m 2445
Hydrocyanation (DuPont) Ni[P(OR3)]4 ∼1000
Ethene-Oligomerization (SHOP) Ni(P^O)-chelate complex 870
Acetic acid (Eastman Kodak) HRhI2(CO)2 / HI / CH3I 1200
Acetic acid anhydride (Tennessee-Eastman) HRhI2(CO)2 / HI / CH3I 227
Metolachlor (Novartis) [Ir(ferrocenyldiphosphine]I / H2SO4 10
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Citronellal (Takasago) [Rh(binap)(cod)]BF4 1,5
Indenoxide (Merck) chiral Mn(salen)-complex 600 kg scale
Glycidol (ARCO, SIPSY) Ti(OiPr)4 / diethyl tartrate several tons
Homogeneous CatalysisHomogeneous CatalysisOverviewOverview•• IntroductionIntroduction
History, general principles & aspectsHistory, general principles & aspects•• OrganometallicsOrganometallics
•• Elementary Reaction StepsElementary Reaction Steps
•• Homogeneous Homogeneous Catalytic ProcessesCatalytic ProcessesHydrogenationHydrogenationHydroformylationHydroformylationCarbonylation of Methanol (Carbonylation of Methanol (Monsanto acetic acid & Monsanto acetic acid & acetic anhydride process)acetic anhydride process)
•• ConceptsConcepts
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HydrocyanationHydrocyanationWackerWacker--Hoechst OxidationHoechst OxidationOligomerizationOligomerizationMetathesisMetathesisPolymerizationPolymerization
50
Homogeneous HydrogenationHomogeneous Hydrogenation•• Wilkinson’s catalyst 1965 Wilkinson’s catalyst 1965 RhCl(PPhRhCl(PPh33))33
1st homogeneous hydrogenation catalyst1st homogeneous hydrogenation catalyst
Synthesis of the catalystSynthesis of the catalystEtOH
RhCl3 * 3 H2O + exc. PPh3
EtOH
80°CRhCl(PPh3)3 + 2 HCl + Ph3P=O
dd6644
IIIIII II
Reversible coordination of etheneReversible coordination of ethene
RhCl(PPh3)3 +20°C
trans-RhCl(C2H4)(PPh3)2 + PPh3
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R coordinates less by a factor of 2000coordinates less by a factor of 2000
Irreversible coordination of COIrreversible coordination of CO
RhCl(PPh3)3 + CO20°C
trans-RhCl(CO)(PPh3)2 + PPh3
e.g. decarbonylation of aldehydes can lead to the deactivation of the catalyste.g. decarbonylation of aldehydes can lead to the deactivation of the catalyst
Homogeneous HydrogenationHomogeneous Hydrogenation
oxidative additionreductiveelimination
H2
RhL
LCl
L
LLH
R
H H
RhL
H
R
LL
RhL
ClL
HL
RhL
ClL
H
H
H
liganddissociation
RhCl
LH
LR
H
RhCl
L
RHL
ligandassociation
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alkenecoordinationR
RhL
ClL
H
R
H
migratoryinsertion
•• HH22 activation is the rate limiting stepactivation is the rate limiting step
51
Homogeneous HydrogenationHomogeneous Hydrogenation
Cp* La HR R
Lanthanocene hydride catalystsame transformation, very different cycle!
σ-bondmetathesis
Cp*2LaH
H δ+δ+
δ-
δ-Cp*2La
H
R
Cp*2La Holefincoordination
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R
δ+ δ-
H2Cp*2La
R
H
migratoryinsertion
Hessen/Elsevier
•• The least substituted C=C bond is hydrogenated fastestThe least substituted C=C bond is hydrogenated fastest
Homogeneous HydrogenationHomogeneous Hydrogenation
R» » > »
•• For simple alkenes manly steric factors determine the reactivityFor simple alkenes manly steric factors determine the reactivity
terminal > internalcis > trans
hydrogenation is stereospecific hydrogenation is stereospecific ciscis
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low tendency towards isomerizationlow tendency towards isomerization
tolerated functional groups:tolerated functional groups: COOH, COOR, CN, NO2, O
strongly coordinating strongly coordinating substratessubstrates inhibit:inhibit: NH2 COOH;
52
Asymmetric HydrogenationAsymmetric HydrogenationCOOR
NHAcMeO
OAc
H2
[Rh(dipamp)]+ NH2
COOH
HOOH
OMe
LL--DOPADOPA
•• Monsanto’s LMonsanto’s L--DOPA processDOPA processLL DOPA is an agent against Parkinson’s diseaseDOPA is an agent against Parkinson’s disease
P P
MeO
DIPAMP
+N
COOMeHN
MeOOC H +
RhS
SP
P*+
ArNHCOMe
COOMe+
LL--DOPA is an agent against Parkinson’s diseaseDOPA is an agent against Parkinson’s disease
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+ RhP
P *ArOH3C
RhP
P* ArO CH3
kR kS
majormajordiastereomerdiastereomer
minorminordiastereomerdiastereomer
kS » kR
((SS))--product formed predominantlyproduct formed predominantly
NO
HNO N
OClO
[I (I) K t ]
Asymmetric Hydrogenation of IminesAsymmetric Hydrogenation of IminesApplication of Chiral Ferrocenyl Phosphines at CIBAApplication of Chiral Ferrocenyl Phosphines at CIBA
[Ir(I) Kat.]
((SS))--metolachlor, metolachlor, herbizideherbizideee = 80 %ee = 80 %
I (I) / li d / i did / HI (I) / li d / i did / H SOSOPchiral ligand
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Ir(I) / ligand / iodide / HIr(I) / ligand / iodide / H22SOSO44substrate / Ir < 1 000 000substrate / Ir < 1 000 000
PPh2Fe2
g
H.-U. Blaser, H.-P. Buser, R. Häusel, H.-P. Jalett, F. Spindler, J. Organomet. Chem. 2001, 621, 34-38.H.-U. Blaser, M. Studer, Applied Catalysis A: General 1999, 189, 191-204.
Asymm_01
53
Other Chiral DiphosphinesOther Chiral DiphosphinesApplicationApplication
99 % e.e.100 bar H2
NEt3
Ru(BINAP)(RCO2)2
R R
O O
R R
OH O
PPh2
P
RR
R
NCH3 N
F
NO
OCO2H
OHOH
OHO ((R)-BINAP)Ru2+
H2 70 bar
Levofloxacin
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PPh2
PPh2P
R
R
RR--DuPhosDuPhos SS--BINAPBINAP
A. Miyashita, …., R. Noyori,J. Am.Chem. Soc. 1980, 102, 7932.
M.J. Burk, J.E. Harlow,J. Am.Chem. Soc. 1992, 114, 6266.
Hessen/Elsevier
Phosphorus LigandsPhosphorus Ligandsfor Asymmetric Hydrogenationfor Asymmetric Hydrogenation
PCy2
PCy2
FeP
P
PPh2PPh2
O OPh2P PPh2P P
OMe
Josiphos
Spindler, Togni 1994
P
DuPHOS
Burk 1990
2
BINAP
Noyori 1980Kagan 1972
Ph2P PPh2
CHIRAPHOS
Bosnich 1977
MeO
Knowles 1972
PPhOOPh
P tBuPPh2
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PPh2PPh2
BIPHEMP
Schmid 1988
OO
P OR*
Reetz 2000
OO
P N
Ph
Feringa 2000
PtBu
tBuHH
TangPhos
Zhang 2002
PPh2
Phanephos
Pye, Rossen 1997
54
Homogeneous CatalysisHomogeneous CatalysisOverviewOverview•• IntroductionIntroduction
History, general principles & aspectsHistory, general principles & aspects•• OrganometallicsOrganometallics
•• Elementary Reaction StepsElementary Reaction Steps
•• Homogeneous Homogeneous Catalytic ProcessesCatalytic ProcessesHydrogenationHydrogenationHydroformylationHydroformylationCarbonylation of Methanol (Carbonylation of Methanol (Monsanto acetic acid & Monsanto acetic acid & acetic anhydride process)acetic anhydride process)
•• ConceptsConcepts
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HydrocyanationHydrocyanationWackerWacker--Hoechst OxidationHoechst OxidationOligomerizationOligomerizationMetathesisMetathesisPolymerizationPolymerization
HydroformylationHydroformylation
•• The hThe hydroformylation reaction was found by O. Roelen in 1938 during his ydroformylation reaction was found by O. Roelen in 1938 during his work on Fischerwork on Fischer Tropsch synthesisTropsch synthesis
R R
CHO
RCHO+
CO/H2
[catalyst]
work on Fischerwork on Fischer--Tropsch synthesisTropsch synthesis
Very important reaction for the production of softeners for plastics and Very important reaction for the production of softeners for plastics and detergent alcohols.detergent alcohols.
Bulky substituents increase the linearity of the product.Bulky substituents increase the linearity of the product.
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Acceptor ligands increase the rate of the reaction by accelerating ligand and Acceptor ligands increase the rate of the reaction by accelerating ligand and CO dissociation and olefin coordination.CO dissociation and olefin coordination.Acceptor ligands increase the ratio of linear productAcceptor ligands increase the ratio of linear product..
55
Catalyst Co(CO)4H Co(PBu3)(CO)3H Rh(CO)4H Rh(TPP)3(CO)H Rh(TPPTS)3(CO)H
T 110-180°C 160-200°C 100-140°C 85-115°C 50-130°C
p 200-350 bar 30-100 bar 200-300 bar 15-20 bar 10-100 bar
Products aldehydes alcohols aldehydes aldehydes aldehydes
Industrial Hydroformylation Overview Industrial Hydroformylation Overview
l/b (propene) 80:20 88:12 50:50 92:8 95:5
Byproducts medium high low low low
Poisoning low medium high - high
Feed stocks C2-C20 Higher alkenes spec. alkenes,ethene
lower alkenes lower alkenes
Processes RuhrchemieBASFKuhlmann
Shell - LPO Ruhrchemie/RhônePoulenc
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Separationcat./product
several distillation underincreasedpressure
- distillation phase separation
Catalystrecycling
several in residue - cat. remains inreactor
in aqueous phase
HydroformylationHydroformylation
Formation of the catalyst complexFormation of the catalyst complex
Co2(CO)8H2
2 HCo(CO)4•• Cobalt systems:Cobalt systems:
At high Rh concentration and low pressure there is an equilibrium between At high Rh concentration and low pressure there is an equilibrium between catalytically inactive dimeric species and the active hydride.catalytically inactive dimeric species and the active hydride.
(acac)Rh(CO)2
CO/H2 ; L
- Hacac
HRhCO
COLL•• Rhodium systems:Rhodium systems:
SchuitSchuit Institute of Catalysis Institute of Catalysis
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2 Rh
H
CO
COL
L+ H2
C
CRhL
L
LRhC
C L
O O
OO
cata yt ca y act e d e c spec es a d t e act e yd decata yt ca y act e d e c spec es a d t e act e yd de
56
Hydroformylation Hydroformylation (Cobalt(Cobalt--catalyzed)catalyzed)
ROR
COH H
H2
(CO)4Co Co(CO)4
ligandexchange
mechanism?
CO
CO- CO
H2
H
Co
COCO
COR
Co
CO
OCCO
CO
O R
H
Co
CO
OCCO
COexchange
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COCO
COCO
Co
CO
OCCO
CO
R
migratoryinsertion
migratoryinsertion
Hessen/Elsevier
Hydroformylation Hydroformylation (Cobalt(Cobalt--catalyzed)catalyzed)
Sterically demanding phosphines increase linearity
PC20H41 P
(Shell Process)
Co-cat can hydroformylate internal alkenesto linear aldehydes
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to linear aldehydes
- Fast isomerisation of the alkene
- Only conversion to aldehyde via primary alkyl
Hessen/Elsevier
57
HydroformylationHydroformylation•• In most cases CO or ligand In most cases CO or ligand
dissociation is the rate limiting dissociation is the rate limiting step, together with olefin step, together with olefin coordination.coordination.
liganddissociation
R
HRhCO
COLL
H LO R
CO
lk
ν = 18ν = 18
RhCOL
L
HRhCO
LL
RRh
H
COL
HLR
O
alkenecoordination
migratoryinsertion
oxidative addition
reductiveelimination
ν = 16ν = 16
ν = 18ν = 18
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RhCO
COLL
RRhCOL
LRO
RhCOL
L R
CO
H2
ligandassociation
migratoryinsertion
ν = 18ν = 18
ν = 16ν = 16ν = 16ν = 16Type I rate law:Type I rate law:
r =k [H2][Rh]
[CO]-1
RhOCP
R
CHO
R
H
RhP
HydroformylationHydroformylationRegioselectivityRegioselectivity
Rh
CO
OCP R
RCHORh
CO
OCP
P
R
R
Rh
CO
PP
H
Rh
CO
PP
Linearity increases with Tolman cone angleLinearity increases with Tolman cone angle ΘΘ
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Linearity increases with Tolman cone angle Linearity increases with Tolman cone angle ΘΘ
Linearity bulky phosphites > phosphines, BUT: Linearity bulky phosphites > phosphines, BUT:
For very large coneFor very large cone--angle angle Θ Θ only ONE P on Rh only ONE P on Rh fast but also isomerization (see table 6.4)fast but also isomerization (see table 6.4)
Hessen/Elsevier
58
HydroformylationHydroformylationRhodiumRhodium--PhosphitePhosphite
•• Among first ligands used in hydroformylation (apart from PPhAmong first ligands used in hydroformylation (apart from PPh33))
•• Large acceptorLarge acceptor--type ligands: lead to unstable catalysts HRh(CO)type ligands: lead to unstable catalysts HRh(CO)33(P);(P);these are extremely reactive. Only ONE Pthese are extremely reactive. Only ONE P--ligand on metal;ligand on metal;these are extremely reactive. Only ONE Pthese are extremely reactive. Only ONE P ligand on metal; ligand on metal; space limitationspace limitation
This complex may This complex may easily loose COeasily loose CO
OP
OO
R
R
H
Rh
CO
OCCO
P
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•• Fast hydroformylation, also of 2Fast hydroformylation, also of 2--alkenes and other internal alkenes!alkenes and other internal alkenes!Extremely fast for 1Extremely fast for 1--alkenes; high linearity of product.alkenes; high linearity of product.
BUT: also isomerization of 1BUT: also isomerization of 1-- to 2to 2--alkenes alkenes branchedbranched
R Θ = 195Θ = 195οο
Hessen/Elsevier
HydroformylationHydroformylationRhodiumRhodium--PhosphinePhosphine
H H
•• Alkylphosphines: donors Alkylphosphines: donors stabilize Rhstabilize Rh--CO bond;CO bond;hence little COhence little CO--dissociation and very SLOW reaction dissociation and very SLOW reaction
•• Smaller (bidentate) arylphosphines give more stable catalysts;Smaller (bidentate) arylphosphines give more stable catalysts;these are less reactive, and give less linear product these are less reactive, and give less linear product (equil. right hand side)(equil. right hand side)
H
Rh
CO
OCP
P
H
Rh
P
OCCO
P
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•• Larger (bidentate) arylphosphines, especially with high Larger (bidentate) arylphosphines, especially with high χχ--values give more linear product (equil. left hand side)values give more linear product (equil. left hand side)
Hessen/Elsevier
59
Ligand ConceptLigand ConceptChelating ligands possessing a rigid backboneChelating ligands possessing a rigid backbone
P Prigid backbone
(Xantphos(Xantphos--Ligands)Ligands)
P PM
Large bite angle βn
Ar
Ph
Ph
R
H
HSiMe2
X
H, H
βn[°]
102
108
DPEphos
SixantphosO
X RR
SchuitSchuit Institute of Catalysis Institute of Catalysis
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M. Kranenburg, Y.E.M. van der Burgt, P.C.J. Kamer, P.W.N.M. van Leeuwen, K. Goubitz, und J. Fraanje, Organometallics, 1995, 14, 3081.
Ph
Ph
Ph
H
H
Me
SiMe2
S
CMe2
108
109
112Xantphos
Thixantphos
Sixantphos
Xantphos-Ligands
OPAr2PAr2
Hydroformylation of 1Hydroformylation of 1--OcteneOctene
50
60109°
112° 123°
+ CO/H2 CHOCHO
+[Rh-cat.]
10
20
30
40
l/b
l/b --
ratio
ratio
84°
102°
108°
131°
Piet van Leeuwen
SchuitSchuit Institute of Catalysis Institute of Catalysis
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M. Kranenburg, Y.E.M. van der Burgt, P.C.J. Kamer, P.W.N.M. van Leeuwen, K. Goubitz, J. Fraanje, Organometallics, 1995, 14, 3081-3089.
0
DPP
E
DPE
phos
Sixa
nt
Thix
ant
Xant
phos
BIS
BI
DB
Fpho
s
Catgen_sw14
T = 40°C, p = 10 bar CO/H2 (1:1), substrate/Rh = 674, L/Rh = 2.2, [Rh] = 1.78 mM
60
+ CO / H2CHOUnion Carbide,
Rhodium + Phosphine
Catalyst-Recycling V
CO / H2
substrate
productreactor
flashdistillation
HRh(CO)(PPh3)3
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make up purge(tars)
•• low CO pressure•• low temperature•• very hydridic character•• limited to light alkenes !
(volatile aldehydes)
stable in molten PPh3
+ CO / H2CHORuhrchemie/Rhône Poulenc,
Rhodium + Phosphinetwo Phase Process
Catalyst-Recycling VI
CO / H2
substrate
productreactor
HRh(CO)(L)3
decanter
P
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make up purge(tars)
in aqueous layer L =SO3Na 3
•• limited by alkene solubility in water
61
+ CO / H2CHORuhrchemie/Rhône Poulenc,
two Phase Process
gas recycle & off gas
Catalyst-Recycling VII
L =
P
SO N
hydrophilic ligand: TPPTS
organic layerproduct
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SO3Na 3
solubility: > 1 kg / l H2O
•• process intensification
=> reactor & decanter in one unitCO / H2
propene
Homogeneous CatalysisHomogeneous CatalysisOverviewOverview•• IntroductionIntroduction
History, general principles & aspectsHistory, general principles & aspects•• OrganometallicsOrganometallics
•• Elementary Reaction StepsElementary Reaction Steps
•• Homogeneous Homogeneous Catalytic ProcessesCatalytic ProcessesHydrogenationHydrogenationHydroformylationHydroformylationCarbonylation of MethanolCarbonylation of Methanol ((Monsanto acetic acid & Monsanto acetic acid & acetic anhydride process)acetic anhydride process)
•• ConceptsConcepts
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HydrocyanationHydrocyanationWackerWacker--Hoechst OxidationHoechst OxidationOligomerizationOligomerizationMetathesisMetathesisPolymerizationPolymerization
62
Monsanto Acetic Acid ProcessMonsanto Acetic Acid ProcessCarbonylation of MethanolCarbonylation of Methanol
[RhI2(CO)2]-
CH3OH + CO CH3COOH -
oxidativeaddition
RhCO
II
CO
CH3
Imigratoryinsertionli i ili i i
- -
-
RhCO
COI
I
I
COassociation
insertion
RhC
II
COI
CH3
O
II
C CHO
COH3C C
I
OCH3COOH
HI H2O
CH3OH CH3I
ν = 16ν = 16 ν = 16ν = 16
ν = 18ν = 18rate limitingrate limiting
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•• New BP process uses [IrI2(CO)2]- with Ru2(CO)6I2(μ-I)2 as cocatalyst
•• Currently ~ 3.5 Mt/a produced worldwide, 60% of all acetyl compounds based on this process.
reductiveelimination
RhCO
I
I
C
CO
CH3 COI
ν = 18ν = 18
BP Cativa Acetic Acid ProcessBP Cativa Acetic Acid ProcessCarbonylation of Carbonylation of MethanolMethanol
O
IrCO
I
I
CO
Me
Ir
ICO
I
I
CO
MeOH
MeI
HI
H2O
MeO
MeO
I
IrCO
I
II
O
Me
OC
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ratedeterminingCO
MeOH
IrCO
I
II
O
Memigratoryinsertion
Hessen/Elsevier
63
TennesseeTennessee--Eastman, Acetic AnhydrideEastman, Acetic AnhydrideCarbonylation of Methyl AcetateCarbonylation of Methyl Acetate
-
O
oxidativeaddition
RhCO
II
CO
CH3
Imigratoryinsertion
18 18rate limitingrate limiting
[RhI2(CO)2]-H3CC(O)OCH3 + CO CH3C(O)O(O)CCH3
- -
-
H3COO
reductiveli i ti
RhCO
COI
I
COassociation
RhC
II
COI
CH3
O
RhI
IC CH3
OCO
H3C CI
O
LiI
CH3I
LiOO
OO
ν = 16ν = 16 ν = 16ν = 16
ν = 18ν = 18rate limitingrate limiting
SchuitSchuit Institute of Catalysis Institute of Catalysis
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elimination RhCO
ICO
3O
ν = 18ν = 18
•• Process conditions are highly corrosive! => Expensive Hastelloy must be used.
•• Catalyst is stabilized by addition of small amounts of H2.[Rh(CO)2I2]- + 2 HI [Rh(CO)2I4]- + H2
[Rh(CO)2I4]- RhI3 (sol) + 2 CO + I-
TennesseeTennessee--Eastman, Acetic AnhydrideEastman, Acetic AnhydrideCarbonylation of Methyl AcetateCarbonylation of Methyl Acetate
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Flow scheme of the processFlow scheme of the process
64
Homogeneous CatalysisHomogeneous CatalysisOverviewOverview•• IntroductionIntroduction
History, general principles & aspectsHistory, general principles & aspects•• OrganometallicsOrganometallics
•• Elementary Reaction StepsElementary Reaction Steps
•• Homogeneous Homogeneous Catalytic ProcessesCatalytic ProcessesHydrogenationHydrogenationHydroformylationHydroformylationCarbonylation of Methanol (Carbonylation of Methanol (Monsanto acetic acid & Monsanto acetic acid & acetic anhydride process)acetic anhydride process)
•• ConceptsConcepts
SchuitSchuit Institute of Catalysis Institute of Catalysis
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HydrocyanationHydrocyanationWackerWacker--Hoechst OxidationHoechst OxidationOligomerizationOligomerizationMetathesisMetathesisPolymerizationPolymerization
isomerization
n : i = 93 : 7
three step processthree step process
Hydrocyanation of ButadieneHydrocyanation of ButadieneDuPont ADN ProcessDuPont ADN Process
CN + HCN CNNC
Ni[P(O-tol)3]4
+ HCN70°C, low pressurehigh ligand excessHCN dosation
CNCN
+Ni[P(O-tol)3]4
3 : 2
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Nylon 6,6Nylon 6,6
ADNADN[ Lewis acid ]
•• ca. 800.000 t/a ADN
HCN-sw2
65
Mechanism of the Hydrocyanation ReactionMechanism of the Hydrocyanation Reaction
L NiH
CN
LL
- LHCN
CN L
+ L
NiL
L
H
CN
CNL2Ni CN
NiL4 NiL3
- L
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Nickel Nickel -- allyl allyl -- mechanism for 1,3mechanism for 1,3--dienes (L = phosphite)dienes (L = phosphite)
CN
HCN-sw16
Deactivation of the CatalystDeactivation of the Catalyst
L4Ni+ HCN
NiH
CNL
LL
- L
+ L
- L
+ LNNi
LL
H
CN
RL3Ni
- H2+ HCN
L2Ni(CN)Ni(CN)22
•• large excess of ligand necessary
•• HCN concentration has to be low
reaction rates are relatively low
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•• loss of nickel by formation of Ni(CN)2
•• sophisticated engineering concerning HCN injection
•• recycling of the catalyst is expensive
HCN-sw3
66
Considerations About the MechanismConsiderations About the Mechanism
angle
The Role of the Bite AngleThe Role of the Bite Angle
P
NiP
PP
PNC
1
P
7 square planar 90°
1, 4, 6 tretragonal 109°
120°
120°
species structureangle
P - Ni - P
trigonal-bipyr.
trigonal2
3, 5
HCN
P
RNC
P
2 CN
Ni PP
P
H
CN
Ni
PP
R
P
NiPP
6
3
SchuitSchuit Institute of Catalysis Institute of Catalysis
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HCN
P
R
5
CN
NiH
PP
4
CN
NiP
P
H
R
NiP
CNP
CN7
Hydrocyanation of Styrene Applying Xantphos LigandsHydrocyanation of Styrene Applying Xantphos Ligands
30
40
50
60
105°
112°113° 114°
117°
d [%
]
0
10
20
30
P(O
-p-to
l)3
dppe
dppp
dppb
BIN
AP 1a 1b 1c 1d 1e 1f
78° 87° 98° 85°140°
yiel
d
ligand
T = 60°C; t = 18h; L/Ni = 1.2; sty./HCN/Ni = 40 / 40 / 1; a) L/Ni = 5
a)
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1a - f
O
X RR
PAr2PAr2
ligand a b c d e f
X H,H SiMe2 S CMe2 CMe2 -
R H H Me H H H
Ar Ph Ph Ph Ph 3,5-(CF3)2-Ph Ph
Mirko Kranenburg, J. Chem. Commun. 1995, 2177-2178.
HCN-sw7
67
Du Pont ADN Process IDu Pont ADN Process I
CN
isom.reactor
distil.
distil.
flashdistil.reactor
flashdistil.
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catalystmake-up
catalystmake-up
CNcatalystcatalyst
HCN
Du Pont ADN Process IIDu Pont ADN Process II
byproductssolvent
CN
distil.
distil.
liquid-liquid
extraction
flashdistil.reactor
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catalystmake-up
HCN
NCCNcatalyst
68
Hydrocyanation of ButadieneHydrocyanation of ButadieneTriptyceneTriptycene--Based Large Bite Angle LigandsBased Large Bite Angle Ligands
Large defined bite angleLarge defined bite angleVery rigid backboneVery rigid backboneLimited flexibility rangeLimited flexibility range
PPh2Ph2PLimited flexibility rangeLimited flexibility range
Cl1a
Cl1
Pt
P1
P1a
ACH
Ni(cod)2 / LCN +
CN
3-PN 2M3BN
t [h]t [h] Conv. [%]Conv. [%] Sel.Sel.(3PN)(3PN) [%][%]
SchuitSchuit Institute of Catalysis Institute of Catalysis
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XX--ray crystal structure of LPtClray crystal structure of LPtCl22PP--P distance = 3.61 P distance = 3.61 ǺǺPP--PtPt--P bite angle = 107.53P bite angle = 107.53°°
W. Ahlers, R. Paciello, D. Vogt, P. Hofmann (BASF) WO02/083695, (W. Ahlers, R. Paciello, D. Vogt, P. Hofmann (BASF) WO02/083695, (2002)2002)
33 5959 97.897.855 8787 95.395.3
Ni/BD/ACH = 1:100:200; L/Ni = 1; T = 90Ni/BD/ACH = 1:100:200; L/Ni = 1; T = 90°°C;C;0.018 mmol Ni(cod)0.018 mmol Ni(cod)22; 2ml dioxane; 2ml dioxane
L. Bini, et al., L. Bini, et al., J. Am. Chem. Soc.J. Am. Chem. Soc. 20072007, , 129129, 12622., 12622.
last change: 071114
Hydrocyanation of ButadieneHydrocyanation of ButadieneTriptyceneTriptycene--Based Large Bite Angle LigandsBased Large Bite Angle Ligands
P
PNi(cod)
P
3PN
CN
PNi0
PNi0
PP
Ni0P
PNiII
P H
CN
2M3BN HCNPPh2Ph2P
SchuitSchuit Institute of Catalysis Institute of Catalysis
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CNCN
PNiII
P
CN
CN
L. Bini, C. ML. Bini, C. Müllerüller, J. Wilting. L. Chrzanowski, A.L. Spek, D. Vogt, , J. Wilting. L. Chrzanowski, A.L. Spek, D. Vogt, J. Am. Chem. Soc.J. Am. Chem. Soc. 20072007, , 129129, 12622, 12622--12623.12623.
last change: 071114
69
Homogeneous CatalysisHomogeneous CatalysisOverviewOverview•• IntroductionIntroduction
History, general principles & aspectsHistory, general principles & aspects•• OrganometallicsOrganometallics
•• Elementary Reaction StepsElementary Reaction Steps
•• Homogeneous Homogeneous Catalytic ProcessesCatalytic ProcessesHydrogenationHydrogenationHydroformylationHydroformylationCarbonylation of Methanol (Carbonylation of Methanol (Monsanto acetic acid & Monsanto acetic acid & acetic anhydride process)acetic anhydride process)
•• ConceptsConcepts
SchuitSchuit Institute of Catalysis Institute of Catalysis
D. Vogt NIOK CAIA course 2009 Homogeneous CatalysisTUTU//ee NIOKNIOK
HydrocyanationHydrocyanationWackerWacker--Hoechst OxidationHoechst OxidationOligomerizationOligomerizationMetathesisMetathesisPolymerizationPolymerization
Direct Oxidation of EtheneDirect Oxidation of EtheneWacker ProcessWacker Process
[Pd(0)/ Cu(II)]C2H4 + 1/2 O2 CH3CHO
•• An important feature is that the oxygen atom in the product acetaldehyde stems An important feature is that the oxygen atom in the product acetaldehyde stems
C2H4 + PdCl2 + H2O H3CCHO + Pd(0) + 2 HCl
Pd(0) + 2 [CuCl4]2- [PdCl4]2- + 2 [CuCl2]-
2 [C Cl ]- + 1/2 O + 2 HCl 2 CuCl + 2 Cl- + H O
•• The whole process only becomes catalytic by the reoxidation of PdThe whole process only becomes catalytic by the reoxidation of Pd(0)(0) with Cuwith Cu(II)(II)..
from water by nucleophilic attack of the coordinated olefin.from water by nucleophilic attack of the coordinated olefin.
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2 [CuCl2]- + 1/2 O2 + 2 HCl 2 CuCl2 + 2 Cl + H2O
•• Behalf of ethene, all other olefins give the corresponding ketone in the Wacker Behalf of ethene, all other olefins give the corresponding ketone in the Wacker oxidationoxidation..
•• Substitution of water is possible (e.g. by CHSubstitution of water is possible (e.g. by CH33COOH), giving rise to other COOH), giving rise to other productsproducts..
70
Direct Oxidation of EtheneDirect Oxidation of EtheneWacker ProcessWacker Process
[Pd(0)/ Cu(II)]C2H4 + 1/2 O2 CH3CHO
[PdCl4]2-
-Pd
Cl
Cl
Cl- Cl-
2 CuCl1/2 O2
- H2O
2 HClν = 16ν = 16
H2O
Pd0
Cl
PdCl
Cl
H2O
-ClH OPd
Cl
Cl
H2O - - H+
- Cl- H2O
- Cl-- HCl- H2O
2 CuCl2
H3C CH
O
ν = 16ν = 16
ν = 16ν = 16
16 16
nucleophilic attacknucleophilic attackby Hby H22OO
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PdCl
Cl
H2O
OH
OH
PdH
Cl
H2O
OH
- Cl-
+ Cl-ν = 16ν = 16
ν = 16ν = 16
ν = 16ν = 16
d[CH3CHO]
dt= k
[C2H4][PdCl42-]
[H+][Cl-]2
Wacker ProcessWacker Process[Pd(0)/ Cu(II)]
C2H4 + 1/2 O2 CH3CHO
•• One stage processOne stage process
Conversion limited to 35 Conversion limited to 35 -- 40% 40% =>=> gas recycle necessarygas recycle necessary
High purity gases are needed to avoid purges:High purity gases are needed to avoid purges:
Two process variants operated
High purity gases are needed to avoid purges:High purity gases are needed to avoid purges:pure Opure O2299.9 % ethene99.9 % ethene
TiTi--equipment needed (highly corrosive HCl in oxidative medium)equipment needed (highly corrosive HCl in oxidative medium)
But, low pressureBut, low pressure
•• Two stage processTwo stage process
Total conversion of ethene Total conversion of ethene =>=> no gas recycle no gas recycle =>=> raw gases usedraw gases used
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g yg y gg
But higher pressure + two reactors But higher pressure + two reactors =>=> higher investment higher investment
TradeTrade--off betweenoff between •• low investment + costly raw materialslow investment + costly raw materials•• high investment + cheap raw materialshigh investment + cheap raw materials
(determining factor is the price of pure O(determining factor is the price of pure O22 !)!)
71
Homogeneous CatalysisHomogeneous CatalysisOverviewOverview•• IntroductionIntroduction
History, general principles & aspectsHistory, general principles & aspects•• OrganometallicsOrganometallics
•• Elementary Reaction StepsElementary Reaction Steps
•• Homogeneous Homogeneous Catalytic ProcessesCatalytic ProcessesHydrogenationHydrogenationHydroformylationHydroformylationCarbonylation of Methanol (Carbonylation of Methanol (Monsanto acetic acid & Monsanto acetic acid & acetic anhydride process)acetic anhydride process)
•• ConceptsConcepts
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HydrocyanationHydrocyanationWackerWacker--Hoechst OxidationHoechst OxidationOligomerizationOligomerizationMetathesisMetathesisPolymerizationPolymerization
Ethene OligomerizationEthene Oligomerizationαα--OlefinsOlefins
Application Market share ( % ) α-Olefin cutUSA Western
EuropeJapan
αα--Olefin marketsOlefin markets
Europe
Detergents 32 56 35 C10-C20+
Copolymers 26 13 37 C4-C8
Plasticizer 12 8 22 C6-C10
Polyalphaolefins 9 12 * C10
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Polyalphaolefins 9 12 C10
Others 21 11 6
* included in "Others"C. S. Read, R. Willhalm, Y. Yoshida in The Chemical Economics Handbook Marketing Research Report “Linear Alpha-Olefins“, SRI International 1993, 681.5030A.
72
Ethene OligomerizationEthene Oligomerizationαα--OlefinsOlefins
Final Products Olefin Consumption (103 t)
USA Western Europe
Uses of higher linear Uses of higher linear αα--olefins 1992 (Stanford Research Institute)olefins 1992 (Stanford Research Institute)
USA Western Europe
Detergent Alcohols 215 150
Plasticizer Alcohols 91 34
Amines and -Derivatives 25 *
α -Olefinsulfonates (AOS) 10 3
Linear Alkylbenzenes (LAB) 11 40
Copolymers (HDPE LLDPE) 208 60
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Copolymers (HDPE, LLDPE) 208 60
Synthetic Lubricants (SHC) 70 50
Lubricant Additives 25 40
Total 787 385
* unknown
Ethene OligomerizationEthene Oligomerizationαα--OlefinsOlefins
Comparison of product qualities of technical CComparison of product qualities of technical C66--CC1818 αα--Olefins Olefins
Quality [wt. % α-olefin]Wax-cracking Chevron Ethyl SHOP
α-Olefins 83 - 89 91 - 97 63 - 98 96 - 98
Branched olefins 3 - 12 2 - 8 2 - 29 1 - 3
Paraffins 1 - 2 1.4 0.1 - 0.8 0.1
Dienes 3 - 6 - - -
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A. M. Al-Jarallah, J. A. Anabtawi, M. A. B. Siddique, A. M. Aitani, A. W. Al-Sa´doun, Cat. Tod. 1992, 14, 1.
Monoolefins 92 - 95 99 > 99 99.9
73
Ethene OligomerizationEthene OligomerizationShell Higher Olefin Process (SHOP)Shell Higher Olefin Process (SHOP)
NiOO
PPh Ph
- 1,5-CODNi
OO
PPh Ph
H
PPh2
COOHSHOP ligand:SHOP ligand:
pn
en
CH2=CH2
CH =CH
NiO
PH
NiO
PNi
O
P
RnRn
Willi Keim
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p1
p2
CH2=CH2
CH2=CH2
CH2=CH2
NiO
PNi
O
P
e2 e1
p1, p2, p3, ... propargation stepse1, e2, e3, ... elimination steps
50
60
n, %
w C6 - C10C20+
Shell Higher Olefin Process (SHOP)Shell Higher Olefin Process (SHOP)Product DistributionProduct Distribution
0
10
20
30
40
0 4 0 5 0 6 0 65 0 7 0 75 0 8 0 85 0 9
Prod
uct d
istr
ibut
ion
C12-C18
C4
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0,4 0,5 0,6 0,65 0,7 0,75 0,8 0,85 0,9
Growth factor, K
Catalysis_24
•• The chain length of the α-olefins is determined by the geometric factor K of molar growth
74
Shell Higher Olefin Process (SHOP)Shell Higher Olefin Process (SHOP)
products
reactors
phaseseparation
C H
Catalyst
C2H4flash
distillation
Catalyst purge
•• The catalyst complex is soluble in butanediol 1 3
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•• 98% linear α-olefins are obtained as important intermediates for low density polyolefins and detergents.
•• The catalyst complex is soluble in butanediol-1,3
•• Shell’s higher olefin process was the first example using a two-phase catalyst separation.
Shell Higher Olefin Process (SHOP)Shell Higher Olefin Process (SHOP)plant principleplant principle
What to do with (relatively low value) 1What to do with (relatively low value) 1--butene and C18butene and C18++ alkenes?alkenes?
•• Isomerize to internal alkenes (Na/K on SiOIsomerize to internal alkenes (Na/K on SiO22 cat.)cat.)
•• Olefin metathesis to intermediate chain length internal Olefin metathesis to intermediate chain length internal alkenes (Coalkenes (Co--Mo oxide catalyst) Mo oxide catalyst)
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•• CoCo--catalyzed hydroformylation that converts internal catalyzed hydroformylation that converts internal alkenes to mainly terminal aldehydesalkenes to mainly terminal aldehydes
Hessen/Elsevier
75
Shell Higher Olefin Process (SHOP)Shell Higher Olefin Process (SHOP)
Ethylene
AO Product DistillationEthylene OligomerizationLight EndsColumn
Heavy EndsColumn
Reaction Separation Product Wash
Catalyst
y
C6 - C8
C8 - C10
C6
C8
C10
Isomerization / Disproportionation
Light RecycleDIST
DIS
IT
Catalyst
Bleed
P PurificationI IsomerizationD Disproportionation
c.w.
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C10 - C11
C11 - C12
C13 - C14
C15 - C19
C10
C12
C14
C16
C18AO Feed
PID
Heavy Recycle
IL
T
LAT
N
IO
ILLAT
N
IO
Internal Olefins alpha - Olefins
Homogeneous CatalysisHomogeneous CatalysisOverviewOverview•• IntroductionIntroduction
History, general principles & aspectsHistory, general principles & aspects•• OrganometallicsOrganometallics
•• Elementary Reaction StepsElementary Reaction Steps
•• Homogeneous Homogeneous Catalytic ProcessesCatalytic ProcessesHydrogenationHydrogenationHydroformylationHydroformylationCarbonylation of Methanol (Carbonylation of Methanol (Monsanto acetic acid & Monsanto acetic acid & acetic anhydride process)acetic anhydride process)
•• ConceptsConcepts
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HydrocyanationHydrocyanationWackerWacker--Hoechst OxidationHoechst OxidationOligomerizationOligomerizationMetathesisMetathesisPolymerizationPolymerization
76
Olefin Metathesis CatalysisOlefin Metathesis CatalysisM CHR
RHC CHR
M CHR
RHC CHR
M
RHC
CHR
CHR
Catalyses:Catalyses:
RHC CHR RHC CHR RHC CHR2+
cross metathesis
ring opening / ring closing metathesis
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g p g g g
CH2H2C
n n H2C CH2+
Hessen/Elsevier
Olefin Metathesis PolymerizationOlefin Metathesis PolymerizationROMP-polymerisation
(ring-opening metathesis)
R
(Acyclic diene metathesis)ADMET-polymerisation
n
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H2C CH2+ n
nX
X
H2CX
CH2
Hessen/Elsevier
77
WellWell--Defined Metathesis CatalystsDefined Metathesis Catalysts
RuClCl CHPh
N N
Mo CHRN
(CF ) CHO ClPCy3(CF3)2CHO
(CF3)2CHO
Mo CHRN
Cy
SchrockGrubbs
Ru catalyst highlytolerant to polar functionalities:
Richard Schrock Bob Grubbs
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OO
Mo CHRy
Cy Schrock/Hoveyda
functionalities:
Highly valuablein organic synthesis
Hessen/Elsevier
Homogeneous CatalysisHomogeneous CatalysisOverviewOverview•• IntroductionIntroduction
History, general principles & aspectsHistory, general principles & aspects•• OrganometallicsOrganometallics
•• Elementary Reaction StepsElementary Reaction Steps
•• Homogeneous Homogeneous Catalytic ProcessesCatalytic ProcessesHydrogenationHydrogenationHydroformylationHydroformylationCarbonylation of Methanol (Carbonylation of Methanol (Monsanto acetic acid & Monsanto acetic acid & acetic anhydride process)acetic anhydride process)
•• ConceptsConcepts
SchuitSchuit Institute of Catalysis Institute of Catalysis
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HydrocyanationHydrocyanationWackerWacker--Hoechst OxidationHoechst OxidationOligomerizationOligomerizationMetathesisMetathesisPolymerizationPolymerization
78
PolyolefinsPolyolefins
By free-radical polymerization:
LDPE : Long-chain branching amorphous polyethene; films, packaging.
B t l t l d l i tiBy metal-catalyzed polymerization:
HDPE: Linear polyethene chain; high strength, stiffness;pipes, containers, caps, closures.
LLDPE: Short-chain branching; properties and use dependent on comonomer type and content.
PP: Isotactic propene homopolymer. High rigidity;ersatile properties large range of applications
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versatile properties; large range of applications
Heterophasic copolymer. Elastomeric (E/P copolymer) phase dispersed in a homopolymer matrix; impact resistant.
Random copolymer. Ethylene and/or butene incorporated into PP chain; improved transparency.
Hessen/Elsevier
World Production PolyetheneWorld Production Polyethene
~ 45 Mt/a in 2000~ 45 Mt/a in 2000
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79
Catalyst Families for Olefin PolymerizationCatalyst Families for Olefin Polymerization
Ziegler catalysts
transition-metal halide + Al-alkyl( ll lid t)(usually on a solid support)
Phillips catalystCr-species on SiO2 support
"Single-site" catalysts
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Single-site catalysts
Well-defined organometallic complexes(can be used in solution or on a solid support)
Hessen/Elsevier
Generations of Ziegler CatalystsGenerations of Ziegler Catalysts
1st TiCl3 / AlEt2Cl
productivity(kg PP/g Ti)
% i-PP
5 90
TiCl3 / isoamylether /AlCl3 / AlEt2Cl
MgCl2 / ester / TiCl4AlEt3 / ester
MgCl2 / ester / TiCl4AlEt / 1 3 di th
15
300
600
95
92
98
2nd
3rd
4th
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AlEt3 / 1,3-diether
MgCl2 support greatly improves effectivity of Ti'external donors' convert sites with poor selectivity to eitherselective or inactive sites
Hessen/Elsevier
80
CosseeCossee--Arlman MechanismArlman Mechanism(migratory insertion)
CH2R
MXX
CH2R
MXX CH2ethene
M
X
X
X
CH2RCH CH R
M
X
X
X CH2
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M
X
X
X
X CH2
CH2M
X
X
X
XCH2
CH2 CH2R
Hessen/Elsevier
Alkene PolymerizationAlkene Polymerization
•• Cossee Cossee -- Arlman MechanismArlman Mechanism
Cl Cl
[TiCl3]n
AlEt3
polyethylene Cl
ClTi
Cl
Cl
ClTi
ClCl
ClTi
Cl
polyethylene
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Cl
ClTi
Cl
Catalysis_27
81
Isospecific Active Sites in Ziegler-Natta Catalysis
Cl Ti
Cl*R
Cl M
L*R
TiCl3 MgCl2/TiCl4/donor
Cl Ti Cl
ClTiCl
Cl Ti Cl
ClML
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L = donor or Cl
•• Site determines orientation of chain ; monomer minimizes interaction with chain
•• Stereospecificity by enantiomorphic site control
Hessen/Elsevier
Single-Site (Zirconocene) Polymerization Catalyst(Sinn, Kaminski; 1978-1980)
cocatalyst: MAO = methylalumoxane = "[(CH3)AlO]n"
MAOMAO
ethene
ZrCH3
ZrCH3
CH3Zr
Cl
Cl- CH3[MAO]
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Zr CH3 ZrCH3
ZrCH3
Hessen/Elsevier
82
Alkene PolymerizationAlkene PolymerizationFliping Mechanism for MetallocenesFliping Mechanism for Metallocenes
•• catalyst activationcatalyst activation
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AlO
AlO
AlO
Al+ZrClCl
Zr CH3MAO
Methylaluminoxane (MAO)Methylaluminoxane (MAO)
•• catalyst activationcatalyst activation
Selective Polymerization of PropeneSelective Polymerization of Propene
C2vTiClCl
atactic
C2ZrClCl
isotactic
HansHans--H. BrintzingerH. Brintzinger
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W. Kaminsky, M. Arndt in Appl. Homog. Catal. with Organomet. Comp. (Eds.: B. Cornils, W. A. Herrmann) Vol. 1, VCH 1996, pp. 220-236.
CSHfClCl
syndiotactic
83
Propene PolymerizationPropene PolymerizationAnalysis of relative stereochemistryAnalysis of relative stereochemistry
m m m rrm m m m m
r = r = rac; rac; m =m = mesomeso
Triad = rmTriad = rmPentad = mmmmPentad = mmmm
mmmm
mmmr mmrr
mrrm
mmrmmmmr
mmmm
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δ 13C
m m m mrm m m m m
δ 13C
One ‘mistake’One ‘mistake’Hessen/Elsevier
Catalytic Trimerization of Ethene
B(C6F5)3 Ti MeMe
TiMe
MeMe
ethene1-hexene
[MeB(C6F5)3]
+ Ti
1-hexene+ Ti
2 ethene
+ TiH
proposed catalyticcycle
involves Ti(IV)-Ti(II)states
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+ Tiethene
H statesinduced by coordinated arene
Hessen et al. Organometallics 21 (2002) 5122Budzelaar et al. Organometallics 22 (2003) 2564
Hessen/Elsevier
84
Chromium Trimerization Catalysts
+ MAO
N NN
R'R'
R'
CrR R
R
Cr(O2CR)3
AlEt3HN
WO 00/58319 (BASF)
Koehn et al. Angew. Chem.Int. Ed. 39 (2000) 4337
1-alkene trimerisationR
ethene trimerisationPhillips petroleumvarious patents
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WO 02/04119 (BP)
high activity ethene trimerisation
+ MAOCr
PN
P
O
Ar
Ar
Ar
RR R
Wass et al.Chem. Commun.(2002) 858
Hessen/Elsevier
Polymerization Catalysts Late Transition Metals
iPrNO
AriPr
iPrNN
Pd
iPr
iPriPrNi
PhMeCN
PdMe OEt2
Brookhart, Johnson Bennett, Grubbs
tolerant of functional groups, but slow + poor comonomer incorporation
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iPr
iPr
NN
Fe
iPr
iPrN
Cl Cl/ MAO
Brookhart,Small, BennettGibson
highly active, but mainlyfor ethene polym./oligom.
Hessen/Elsevier
85
NNNi
Br BrNN
Ni
Br Br
NNNi
Br Br
Polyethene with Designer CalalystsPolyethene with Designer Calalysts
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highly branchedhighly branched=> rubber, elastic=> rubber, elastic
polymer with short branchespolymer with short branches=> soft, films=> soft, films
highly linear polymerhighly linear polymer=> hard, fibers=> hard, fibers
SupplementSupplement
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Homogeneous CatalysisHomogeneous CatalysisOverviewOverview•• IntroductionIntroduction
History, general principles & aspectsHistory, general principles & aspects•• OrganometallicsOrganometallics
•• Elementary Reaction StepsElementary Reaction Steps
•• Homogeneous Homogeneous Catalytic ProcessesCatalytic ProcessesHydrogenationHydrogenationHydroformylationHydroformylationCarbonylation of Methanol (Carbonylation of Methanol (Monsanto acetic acid & Monsanto acetic acid & acetic anhydride process)acetic anhydride process)
•• ConceptsConcepts
SchuitSchuit Institute of Catalysis Institute of Catalysis
D. Vogt NIOK CAIA course 2009 Homogeneous CatalysisTUTU//ee NIOKNIOK
HydrocyanationHydrocyanationWackerWacker--Hoechst OxidationHoechst OxidationOligomerizationOligomerizationMetathesisMetathesisPolymerizationPolymerization
Catalytic Cycle and Elementary StepsCatalytic Cycle and Elementary Steps
- LLn-1M
HH
YY 18 16 18 16
oxidative additionoxidative addition
++ HHYY
Ln-2MHH
YY
RHH
-- LLMMLLnn MMLLnn--11
dissociationdissociation
ν = 18, 16ν = 18, 16 ν = 16, 14ν = 16, 14
ν = 18, 16ν = 18, 16
ν = 16, 14ν = 16, 14
dissociationdissociation
associationassociationν = 18, 16ν = 18, 16reductive eliminationreductive elimination
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+ L RLn-2M
YY
HH
RYY
HH
ν = 16, 14ν = 16, 14
insertioninsertionassociationassociation
ν = 18, 16ν = 18, 16
Catgen_sw1
87
Elementary Reaction StepsElementary Reaction Steps
Catalytic Cycles are Composed of sequential Catalytic Cycles are Composed of sequential elementary reaction stepselementary reaction steps
•• ligand coordination/ dissociation/ exchangeligand coordination/ dissociation/ exchange•• migratory insertion/ deinsertionmigratory insertion/ deinsertion•• nucleophilic or electrophilic attacknucleophilic or electrophilic attack•• oxidative addition/ reductive eliminationoxidative addition/ reductive elimination
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•• oxidative coupling/ reductive cleavageoxidative coupling/ reductive cleavage•• cycloaddition reactions (reversible)cycloaddition reactions (reversible)
Hessen/Elsevier
Reaction Mechanisms of dReaction Mechanisms of d--Metal ComplexesMetal ComplexesLigand Substitution ReactionsLigand Substitution Reactions
•• For a consideration of the rates of reactions, the thermodynamic formation For a consideration of the rates of reactions, the thermodynamic formation constant is not a useful measure.constant is not a useful measure.
TheThe nucleophilicitynucleophilicity describes thedescribes the rate of attackrate of attack of a certain ligand (Lewisof a certain ligand (LewisThe The nucleophilicitynucleophilicity describes the describes the rate of attackrate of attack of a certain ligand (Lewis of a certain ligand (Lewis base) relative to another reference in a nucleophilic substitution reaction.base) relative to another reference in a nucleophilic substitution reaction.
Reaction rates are always relative to another rate, set as standard!Reaction rates are always relative to another rate, set as standard!
•• Substitution reactions span a wide range of ratesSubstitution reactions span a wide range of rates
-- Aqua complexes of group 1, 2, and 12 metal ions, lanthanide ions, and Aqua complexes of group 1, 2, and 12 metal ions, lanthanide ions, and some 3d metal ions exchange within nanosecondssome 3d metal ions exchange within nanoseconds
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some 3d metal ions exchange within nanoseconds.some 3d metal ions exchange within nanoseconds.
-- Heavier d metals in higher oxidation states like Ir(III) or Pt(IV) can have Heavier d metals in higher oxidation states like Ir(III) or Pt(IV) can have halfhalf--lives of up to years.lives of up to years.
•• Spectator ligandsSpectator ligands are present in a complex, but not exchanged.are present in a complex, but not exchanged.They can influence the rate of an exchange reaction.They can influence the rate of an exchange reaction.
React_mech_2
88
Ligand Displacement ReactionsLigand Displacement Reactions
M L ML
XM X
X
L
associative
L
M L ML
X
M X
XSN2-like
L
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- LM L M M X
dissociative+ X
L
Hessen/Elsevier
The The transtrans EffectEffect•• A strong A strong σσ--donor or donor or ππ--acceptor ligand greatly accelerates the acceptor ligand greatly accelerates the
substitution of a ligand in substitution of a ligand in transtrans positionposition
Substitutions on sqpl complexes proceed almost invariably via an Substitutions on sqpl complexes proceed almost invariably via an associative rateassociative rate--limiting stage.limiting stage.
σσ--donor donor : : OHOH-- < NH< NH33 < Cl< Cl-- < Br< Br-- < CN< CN--, CO, CH, CO, CH33-- < I< I-- < SCN< SCN-- < PR< PR33 < H< H--
ππ--acceptoracceptor : : BrBr-- < I< I-- < NCS< NCS-- < NO< NO22-- < CN< CN-- < CO, C< CO, C22HH44
transtrans--effecteffect
Effect of the trans ligand in substitutions of Effect of the trans ligand in substitutions of transtrans--[PtCl[PtClLL(PEt(PEt33))22]]
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L k 1/s-1 k 2/(L m ol-1s-1)C H 3
- 1.7 10 -4 6 .7 10 -2
C 6H 5- 3.3 10 -5 1 .6 10 -2
C l- 1 .0 10 -6 4 .0 10 -4
H - 1.8 10 -2 4 .2PEt3 1.7 10 -2 3 .8
89
The The transtrans EffectEffect•• The greater the overlap of ligand orbitals with either a The greater the overlap of ligand orbitals with either a σσ-- or or ππ--Pt 5d Pt 5d
orbital, the stronger the orbital, the stronger the transtrans effect.effect.This is in line with a large ligandThis is in line with a large ligand--field splitting.field splitting.
X
CM
C
T
X•• ππ--acceptor ligands facilitate acceptor ligands facilitate nucleophilicnucleophilic attack on a dattack on a d--metal atom by removing emetal atom by removing e--
CM
C
T XC
M
C
T
Y
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Y
React_mech_21
metal atom by removing emetal atom by removing edensity.density.
•• The activated complex has a tbpy structure if the The activated complex has a tbpy structure if the transtrans ligand, Y, and X have complementary ligand, Y, and X have complementary influences on the reaction rate.influences on the reaction rate.
Y
The The transtrans EffectEffectExampleExample
•• How to prepare How to prepare ciscis and and transtrans [PtCl[PtCl22(NH(NH33))22]] starting from starting from [PtCl[PtCl44]]22-- or or [Pt(NH[Pt(NH33))44]]2+2+ ??
ClCl-- has the stronger has the stronger transtrans effect effect =>=> the ammonia in the ammonia in transtrans position is substituted in the second stepposition is substituted in the second step
H3NPt
NH3
H3N NH32+ HCl
H3NPt
ClH3N NH3 HCl
H3NPt
ClCl NH3
+
-- NHNH44XX -- NHNH44XXtranstrans
PtCl Cl 2- NH3 Pt
Cl Cl - NH3 PtCl NH3
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again Clagain Cl-- has the stronger has the stronger transtrans effect effect =>=> the second ammonia is introduced in the second ammonia is introduced in ciscis positionposition
ClPt
Cl ClPt
NH3 ClPt
NH3
3
-- MClMCl -- MClMClciscis
90
Steric EffectsSteric Effects
•• Hydrolysis of Hydrolysis of ciscis--[PtClL(PEt[PtClL(PEt33))22] ] at 25 at 25 °°CC
Steric crowding at the reaction center usually inhibits associative reactions Steric crowding at the reaction center usually inhibits associative reactions and facilitates dissociative reactions.and facilitates dissociative reactions.
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k /sk /s--11 8x108x10--22 2x102x10--44 1x101x10--66
Migratory Insertion ReactionMigratory Insertion Reaction
Homogeneous CatalysisHomogeneous CatalysisElementary StepsElementary Steps
MeCO
COCO
Me
Mechanism supported by IR and Mechanism supported by IR and 1313C NMR studiesC NMR studies
Methyl migration by nucleophilic attack at the carbonyl CMethyl migration by nucleophilic attack at the carbonyl C--atomatom
Mn
CO
OC* CO
OC
COMn
CO
C* CO
OC
CO
O
+ CO
Acyl complexAcyl complex
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ΔS‡ = = --88.2 JK 88.2 JK --11molmol--11
Migratory insertion reactions play an important role in many catalytic Migratory insertion reactions play an important role in many catalytic carbonylation reactions, alkene polymerizations and other reactions carbonylation reactions, alkene polymerizations and other reactions involving substrates with ‘double’ bondsinvolving substrates with ‘double’ bonds
91
Mechanism of COMechanism of CO--Migratory InsertionMigratory Insertion
1313C label shows: Me migrates to cisC label shows: Me migrates to cis--COCO(in fact, the reverse reaction was studied; principle of (in fact, the reverse reaction was studied; principle of ‘ i i ibilit ’ li d)‘ i i ibilit ’ li d)‘microscopic reversibility’ applied)‘microscopic reversibility’ applied)
Me
Mn
CO
OC* CO
OC
COMn
CO
C* CO
OC
COMe
O
+ CO
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CO
Mn
CO
C* CO
OC
COMe
O
Hessen/Elsevier
Homogeneous CatalysisHomogeneous CatalysisElementary StepsElementary Steps
Migratory insertionMigratory insertion
H
MCH2
CH2M
CH2CH3
ββ--EliminationEliminationH H
Metal(hydride) alkene complexMetal(hydride) alkene complex Metal alkyl complexMetal alkyl complex
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MCH2CH3
MCH2
CH H
M
HCH2
CH2
ββ--Hydrogen is abstracted via a cyclic 4Hydrogen is abstracted via a cyclic 4--membered transition statemembered transition state
Hessen/Elsevier
92
Homogeneous CatalysisHomogeneous CatalysisMechanismMechanism Elementary StepsElementary Steps
Migratory deMigratory de--insertioninsertion
CO CH3
Opposite of migratory insertionOpposite of migratory insertion
CO
Mn
CO
C* CO
OC
COMe
OMn
CO
C* CO
OC
COMe
O
CH3
Mn
CO
CO
OC
COOC*
- CO
ββ--EliminationElimination Needs ‘open’ coordination siteNeeds ‘open’ coordination site
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ML
CH2 CH3
M
CH2
CH2
H
agostic interaction
MCH2
CH2
H
CH2
CH2M
H
Stabilization of intermediate : agostic interactionStabilization of intermediate : agostic interactionHessen/Elsevier
In fact, most ‘insertions’ involve migration of a In fact, most ‘insertions’ involve migration of a nucleophile onto an unsaturated moiety, which nucleophile onto an unsaturated moiety, which can take place in various ways:can take place in various ways:
X X
Migratory InsertionMigratory Insertion
M
X
A B
XA
M AB
X1,1 migratory insertion
B1 2 migratory insertion
X
18e 16e
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MB
M A1,2 migratory insertion
X migrates with MX migrates with M--X bonding electrons (CHX bonding electrons (CH33--))
and attacks theand attacks the ππ* orbital of A=B* orbital of A=B
Hessen/Elsevier
93
Oxidative AdditionOxidative Addition
P RhOP
O + CH3-I P RhOP
OCH3
ICharacteristics:Characteristics:Oxidation number +2Oxidation number +2Coordination number +2Coordination number +2
•• Nucleophilic attack of lone pair of the metal on carbonNucleophilic attack of lone pair of the metal on carbon
Three important mechanisms for oxidative addition:Three important mechanisms for oxidative addition:
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p pp p
(R3P)4Pd + ClPh
DH
PdClPR3
PR3
Ph
DH + 2 PR3
CH3X > CH3CH2X > CHR2X > CyX X = halogen
00 IIII
The other two important mechanisms:The other two important mechanisms:
Oxidative AdditionOxidative Addition
HH H
•• nonnon--polar addition:polar addition:
IrPR3
XR3POC H2
IrPR3
XR3POC
H H
Ir
X
PR3
HR3POC IIIIIIII
•• radical addition in a stepwise reaction:radical addition in a stepwise reaction:
Concerted addition; nonConcerted addition; non--polar TSpolar TS
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IrPMe3
ClMe3POC R
IrPR3
R3PR
Cl
Cl
RBrIr
PR3
R3PR
Cl
ClBr
IIIIIIII
Ir(I)Ir(I) Radical; Ir(II)Radical; Ir(II) Ir(III)Ir(III)
94
OrthoOrtho--MetallationMetallation
•• Via Via oxidative addition of Coxidative addition of C--H:H:
PPhClPPh3PPh
M M –– C C 120 120 –– 240 kJ/mol240 kJ/molM M –– H H 200 200 –– 280 kJ/mol280 kJ/molC C –– HH 400 400 –– 440 kJ/mol440 kJ/mol
IrH
PPh3PPh3
PPh2PPh2Ir
Cl
3PPh3
H
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Oxidative addition of COxidative addition of C––C difficult:C difficult:
M M –– C C 120 120 –– 240 kJ/mol240 kJ/mol
C C –– CC 360 360 –– 380 kJ/mol 380 kJ/mol often ‘hidden’ bondoften ‘hidden’ bond
Hessen/Elsevier
Reductive EliminationReductive Elimination
Reductive elimination is the reverse mechanism of Reductive elimination is the reverse mechanism of
•• Usually, both coordination number and oxidation state Usually, both coordination number and oxidation state decrease by two!decrease by two!
oxidative additionoxidative addition
IIIIIIIIRh
ClPPh3OC
Ph3PRh
CH3
OCPh3P
PPh3
O R
Cl
+ RCOCH3
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backback
•• CC--C and CC and C--H (when cis!) easily eliminateH (when cis!) easily eliminate
•• Often last step in catalytic reactionOften last step in catalytic reaction
95
•• Occurs readily for M in high oxidation stateOccurs readily for M in high oxidation state
•• Pt(IV), Pd(IV), Rh(III), Ir(III), Ni(II), Pd(II)Pt(IV), Pd(IV), Rh(III), Ir(III), Ni(II), Pd(II)
•• CC C and CC and C H (H ( hen cis!)hen cis!) easil eliminateeasil eliminate
Reductive EliminationReductive Elimination
•• CC--C and CC and C--H (H (when cis!) when cis!) easily eliminateeasily eliminate
•• Often last step in catalytic reactionOften last step in catalytic reaction
(C(C--H bond forming; hydrogenationH bond forming; hydrogenationCC––C bond forming; hydroformylation etc.)C bond forming; hydroformylation etc.)
P P
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P Pd CH3H3C
P
cis
Pd CH3H3C
P-P
CH3-CH3k = 1/[P]
Hessen/Elsevier
I-
Mechanism of Reductive EliminationMechanism of Reductive Elimination
•• Usually microscopic reverse of oxidative addition Usually microscopic reverse of oxidative addition mechanismmechanism
Ph2P
PtCH3P
Ph2
CH3
CH3
I
Ph2P
PtCH3P
Ph2
CH3
CH3Ph2P
PtCH3P
Ph2
CH3
CH3
PhPh Ph
+
H3C CH3 CH3IPt(IV)Pt(IV)
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Ph2P
PtCH3P
Ph2
CH3Ph2P
PtIP
Ph2
CH3Ph2P
Pt
PPh2
CH3+I-
Pt(II)Pt(II)Pt(II)Pt(II)
Hessen/Elsevier
96
Mechanism of COMechanism of CO--Migratory InsertionMigratory Insertion
(CO)4Mn
L
CO
Me
(CO)4Mn
Me
C O (CO)4Mn CO
Mek1
k-1
L; k2
slow
Rate =-d[Rgt]
dt=
k1k2[L][Rgt]k-1 + k2[L]
if k-1 ~ k2[L]
if k-1 << k2[L]k1[Rgt]-d[Rgt]=
OORgt. Int. Pdct.
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-d[Rgt]dt
= if k-1 >> k2[L]k1k2[L][Rgt]k-1
dt
Hessen/Elsevier
•• MetalMetal--induced coupling with two or more ligands induced coupling with two or more ligands to form a metallacycle:to form a metallacycle:
Oxidative CouplingOxidative Coupling
Moxidative coupling
(reductive cleavage)M
M M
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•• For alkynes easier than for alkenes, faster when For alkynes easier than for alkenes, faster when electronelectron--withdrawing substituents presentwithdrawing substituents present
Hessen/Elsevier
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97
Activation of coordinated substrate:Activation of coordinated substrate:
Nucleophilic attackNucleophilic attack
OH-
2+
+
PdOH
R H
H H
R H
H H
Pd
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Electron density on alkene CElectron density on alkene C--atom lower than in free alkene;atom lower than in free alkene;
Sensitive to nucleophilic attackSensitive to nucleophilic attack
Hessen/Elsevier
σ--Bond MetathesisBond Metathesis
M CH3
H H
M CH3
H H
M CH3
H H
•• Operational for dOperational for d00 complexes, for which oxidative complexes, for which oxidative addition is NOT possibleaddition is NOT possible
M CH3
D3C H
M CH3
D3C H
M CH3
CD3 H
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addition is NOT possibleaddition is NOT possible
•• May beMay be operational for higher doperational for higher dnn configurations, configurations, but not but not quite proven as yetquite proven as yet
Hessen/Elsevier
98
HeterolyticHeterolytic Cleavage of DihydrogenCleavage of Dihydrogen
NEt3(+)
When HWhen H22 is dissociated into His dissociated into H++ and metal hydrideand metal hydride
fast
3+ HNEt3
+
slow
(+)RuL
L HH
H
HRuL
L
RuL
LH
Observed ‘arrested’ intermediate:Observed ‘arrested’ intermediate:
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RuPh2P
PPh2
HH
NMe2RuPh2P
PPh2
NMe2
RuPh2P
PPh2
H H NMe2+
++ H2
‘hydrogen bridge’‘hydrogen bridge’
Hessen/Elsevier
αα--Elimination ReactionsElimination Reactions
M CH2R'R
α-H elimination
- R-H
R HM CHR
R
C-H addition
R-H
α-H elimination
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M NR'R-H
- R-H
C-H addition
M NHR'
R
Hessen/Elsevier
99
22ππ+2+2ππ CycloadditionsCycloadditions
M CHR
RHC CHRRHC CHR
M CHR
M CHR
RC CR
M CHR
RHC CHR
symmetry-forbiddenfor organic reactions:
allowed whentransition-metalis involved
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M CHR
RHC CHRRC CR
M CRis involved
Hessen/Elsevier
Olefin MetathesisOlefin MetathesisA very powerful reaction for cleaving & (re)forming of C=C bondsA very powerful reaction for cleaving & (re)forming of C=C bonds
Nobel Prize 2005 to:Nobel Prize 2005 to: -- Yves ChauvinYves Chauvin-- Richard SchrockRichard Schrock-- Robert GrubbsRobert Grubbs
CHR
CHR
M
RHC
M CHR
RHC CHRRHC CHR
M CHR
Robert GrubbsRobert Grubbs
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+ 2 RHC CHRRHC CHRRHC CHRCatalyses
Hessen/Elsevier
100
PolyolefinsPolyolefinsGlobal PP DemandGlobal PP DemandGlobal PP DemandGlobal PP Demand
kT/a
95%
100%
% OP Rate
Demand
Capacity
Utilisation50 000
55,000
Global PE DemandGlobal PE DemandGlobal PE DemandGlobal PE Demand
kT/a
95%
100%
% OP Rate
Demand
Capacity
Utilisation80,000
90,000
70%
75%
80%
85%
90%
20,000
30,000
40,000
25,000
35,000
45,000
50,000
30,000
40,000
50,000
60,000
70,000
70%
75%
80%
85%
90%
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1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
50%
55%
60%
65%
0
10,000
5,000
15,000
0
10,000
20,000
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
50%
55%
60%
65%
Hessen/Elsevier
Stereocontrol in C2-Zirconocene Catalysts
Pol
Pol
- Ligand dictates conformation of polymer chain
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- Monomer enantioface coordination with least steric hindrance- Two 'sites' on metal related by C2 symmetry: stereopreference is the same
isotactic polymer
Hessen/Elsevier
101
Single-Site Catalysts for Ethene/1-Alkene Copols
Me2SiN
Ti
tBu
R"Constrained geometry catalyst"
(CGC)
Many variations in this systemReview: Waymouth & McKnight Chem. Rev. 98 (1998) 2587
Stevens et al. EP 0416815 (1990; Dow Chemical)
tBu
R''n
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TiNPR'
R'
R'
R
Stephan et al. Organometallics 22 (2003) 1937Nova Chemicals
Hessen/Elsevier
Monocyclopentadienyl Titanium Catalysts:Unusual Behaviour!
(s-PS)syndiotacticpolystyrene
MAOTi
Cl Cl
Tg = 100oCTm = 266oC
Ishihara et al. Macromolecules 21 (1988) 3356
Ph Ph PhPhPhPh PhPhMAOCl
th
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TiH3C
CH3
CH3B(C6F5)3
ethene
toluenesolvent
ethene + 1-hexenecopolymer
Pellecchia et al. Macromolecules 32 (1999) 4419
Hessen/Elsevier
102
Syndiotactic Polymerization of Styrene
PhRRS
Ph PhPhTi
R S RRSTiCp
Ph
Ti
Ph
Cp
- Catalyst is Ti(III): [CpTiR]+
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- Propagation proceeds via 2,1-insertion Catalyst is Ti(III): [CpTiR]
Cavallo et al. Macromolecules 34 (2001) 2459 + 5379
- Calculations on stereoregularity: chain-end control
Hessen/Elsevier
Propene Polymerization: RegioselectivityPropene Polymerization: Regioselectivity
TiPol Pol
Ti[1,2]fast
Ti Pol
TiPol Pol
Ti[2,1]
slow
H Pol
dormant
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Ti H Ti
H2 Pol-
fast fast
Hessen/Elsevier
1
NiL
H3CNi
L
X
NiNi--CC22
H
L
Dimerization of PropeneDimerization of PropeneLigand InfluencesLigand Influences
nn--hexeneshexenes
NiL
XH
CH3
L HH3C
NiX
NiNi--CC11
H
NiL
X
H
CH3
H3C
NiL
X
NiNi--CC11
H
reductive elim.reductive elim.
+
22--methylmethyl--22--pentenepentene
isomerizationisomerization
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NiX
NiNi--CC22
NiNi--CC11
NiL
X
H
X
NiNi--CC22
CH3
B. Bogdanovic, Adv. Organomet. Chem. 1979, 17, 105-140.G. Henrici-Olivé, S. Olivé, Top. Curr. Chem. 1976, 67, 107-127
last change: 071121
2,32,3--dimethyldimethyl--22--butenebutene
Mechanistic Routes to Different ProductsMechanistic Routes to Different Products
NiL
2
Ni
L
2
VCH
*
1,5-COD
+ LL
Ni
Ni[Ni] Ni Ni
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G. Wilke, Angew. Chem. 1988, 100, 189.
ttt-1,5,9-CDT
2
Ni
Catgen_sw8