(2,2',2"-TERPWINE)PLATINUM.@) COMPLEXES OF

PHENYLCYANAMIDE AND 1'4-DICYANAMDO-2,5-

DIMETHYLBENZENE LIGANDS

by

Fahad A.I. AL-mutlaq, B.Sc.

A thesis submitted to

the Faculty of Graduate Snidies and Research

in partial fbifhent of

the requirements for the degree of

Master of Science

Carleton University

Ottawa. ON

December, 1999

Q copyright

1999, Fahad A 1. AL-mutiaq

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Abstract

A series of square p k terpyridineplatinumcLI) complexes of the

p h e n y l c y d d e ligand and its derivatives bas k e n synthesized and

c haracterized by IR ' H NMR UV-Visible spectroscopy, cyclic vo hammetry

and X-ray crystaliography. The crystal structures of [(trpy)Pt@cyd)](PFs) and

[(trpy)R(2,1-Merpcyd)](CF3S03) show that the complexes are planar and the

l?t-NCN bond is bem with angles in the range of 159 to 175'. Since the

formation of n-stacks in the crystal iaîtice requires planarity, the k t that the

molecule is pl- leads to the cornparison with organic charge tramfer sahs

that show n-stacking and are highly conductive. it is suggested that the bending

of the cyanamide group dows for niixing between the +orbital of the metai

and the x* orbital of the ligand ard causes the appearance of the l i g d t o -

metal charge transfer (LMCT) in the visible spectnmi,

Two dinuclear terpyriduieplatinum (II) complexes of derivatives of the

1,44cyanamido bernue dianion ( c i i~~d )~ - were also syntfiesized and

chcterized by IR, 'H NMFt, W-Visible spectroscopy, a d cyclic

vokammetry.

iii

Acknowieàgements

FHst, 1 wish to thank Dr. Robert J. Crutchley, my research supervisor,

for his direction aad guidance throughout my the as his snident.

I would especially like to thank the Kingdom of Saudi Arabia,

represented by the Generai Organization of Technical Education and Vocational

Training Technicd Education for Ml financiai support ,and the Saudi Arabian

Cultural Mission in Caoada Tbanks are also necessary to Dr. Darrin Richeson,

for the elemental d y s e s , Dr. Glenn Yap, for X-ray Crystallography; to Keith

Bourque for the NMR specrra; and Tony O'Neil for the infuared spectm

Finally, 1 would Iike to thad my coileagues: Dr. Chris White, Maria

DeRosa, Peter Mosher and any other people who have assisted me during my

tirne at Carleton.

Table of Contents

Absfract

Acbwledgements

Dedication

Table of CoIItenks

List of Tables

List of Figures

List of Abbreviat ions

CHAPTER 1: Introduction

1.1 Background Information

Page

iii

iv

v

vi

ix

X

xiv

1.1.1 Introduction to Molecular Metals 1

1.1.2 Chemistry of Starting Materials 6

CHUTER 2: Esperimentai Section

Starting Mat&

Rcagents for Ligand Synthesis

Reagents for Complex Synthesis

CompmsedGaPes

So lvents

Soivents of the Synthesis

U.V. Solvent

NMR Solvent

2.2.4 Cyck Voltsmmetry Electrolyte and Solvent 17

2.3 S ynthesis of the Ligands 17

2.3.1 Thailium saits of P h e n y l c y d d e derivatives 17

2.3.1.1 General Description 17

2.3.1.2 Ligand S ynthesis of Phenylcyanamide and its Derivatives 20

2.3 1 Thallium Salts of the 1.4-Dicyanamidobeazew Derivatives 22

2.3.2.1 G e n d Description

2.3.2.2 Ligand Synthesis of 1,4-Dicyanamidobernene

hfbred SP=QQ=PY

Spectroscopy of NMR

Electronic Absorption Spectroscopy

C yclic Voltammetry

X-Ray Crystaüography

Elementai Analysk

CHAPTER 3: Monoauclear Compkxes of Phenylcyanamide Ligands: Physical CharacteMtion and Discussion

Inhred Speciroscopy 36

Roton NMR Spectroscopy 40

Electronic Absorption S pectro sco py 45

Cyclic Voltarnrnetry 50

X-Ray Structure Detefmination 54

X-ray hr [(Q~)R@cyd)l [PF6] 55

X- ray structure for [(trpy)Pt(2,4Me~-pcyd)] [CF3SOp] 55

CHAPTER 4: Diiuclear Compkxes of Dicyaaamidobenzene Ligands: Pbysical Characteriution and Discassion

4.2 Roton NMR Spectroscopy 81

4.3 Electronic Absorption S pectroscopy 83

CHAPTER 5: Summary and Future Work 90

List of Tables

Table Description

IR Data for the Mononuclear Phenylcyanamide Complexes

'H NMR Spectroscopy Daia for [(trpy)~t.L]' Complexes

UV-vis Absorption Data for [(trpy)PtL]' Complexes

Electrochemical Data for Mononuclear Plat inum Complexes

Crystai data and structure r e h e n t for [(trpy)Pt@cyd)]pF6]

Atomic Coordinates and equivalent isotropic displacement for [(trpy)Pt(pcyd~l(PFs)

Crystal data and structure refinement for [(trpy)Pt(2,4-Mez- PCY~)] [03so3 1

IR Data for the DUiuclear ~ i c ~ d ' - Complexes

' H NMR Spectroscopy Data for [ ( t ~ p ~ ) ~ t ~ ] 2 ~ ' Complexes

UV-vis Absorption Daia for [{(trpy)pt ) Complexes

Electrochemical Data for huclear Plathum Complexes

Page

39

41

16

51

57

59

60

63

71

74

79

81

84

86

List of Figures

Figure Description Page

1

3

4

5

5

7

8

9

10

12

37

37

38

38

39

Proton numbering schemes for momnuclear complexes of platinun 40

400 MHz 'H NMR spectrum of [(apy)PtCI](PF6) in cl6-DMSO 41

400 MHz 'H NMR spectnim of [(trpy)Pt@cyd)](PFh) in 4- DMSO 42

3.9 400 MHz 'H NMR spectrum of [(apy)Pt(3,5-Me2pcyd)](PF6) in 4-DMSO (terpyridme and pcyd peaks) 42

üV-vis absorption spectrum of [(trpy)Pt(3,5-Me2pcyd)](PFi) in CH3CN (3 .O0 x 1 O-%)

ü W r i s absorption tnxn of [(apy)Pt(Chpcyd)](PF6) ia CH3CN (3.00 x 1 O- 5

Cyclic Vottammognun of [(trpy)PtCl](Ph) in distilled DMF

Cyciic Vo l t a m m o m of [(trpy)Pt(3,5 -Metpcyd)](Ph) in distilled DMF

ORTEP drawing for the complex [(trpy)Pt(2,4-Me2pcyd)] (cF3so3) 64

ORTEP hwing for the complex [(trpy)Pt(2,4-M~pcyd)] (CF3SO3) 65

ORTEP Qawing for the complex [(trpy)Pt(2,4-Me2pcyd)] (CF3SO3) 66

Unit-Ce11 diagram for the mmplex [(qy)Pt(2,4-Me2pcyd)] (cF3so3) 67

Unit-Cell diagram for the complex [(npy)Pt(2,4-Mezpcyd)] (m3so3) 68

Stereoview for the complex [(trpy)Pt(2,4Mqpcyd)] (CFnSO3) 69

Stereoview for the complex [(trpy)Pî(2,4-Me2pcyd)] (CF3S03) 70

400 MHz 'H NMR spectrum of [{(t~py)Pt)~p-Medi~yd](PFs)~ ia d6-DMSO (t-yridk peaks) 82

400 MHz 'H NMR spectnmi of [{(t~)Pt)~-p-Cl&yd] (CF3S03h in &-DMSO 83

W-vis absorption spccmun of [((t~py)Pt)~-p-Me~dicyd] (PF& in distüled DMF (3.00 x 10'SM) 84

4.10 Cyclic voltammogram of [{(trpy)Pt )2-p-Cihdicyd](CF3SO3h in distillecl DMF 88

4.11 Cyclicvoltammogram~f[{(trpy)Pt}~-p-Chdicyd](CF~SO~)~ in distilled DMF 88

List of Abbreviatiom

*Y

TMS

Pcyd-

~icyd'-

Dip

methyl

dic hloro

pheny lc yaoamide

Chapter 1

Introduction

1.1 Background information

1.1.1 Introduction to Molecuhr Metais

In ment years, many materials with remarkable electronic properties have been

synthesized. Among these are the molecular met&, which are generally composed of

radical ions derived fi0 m donon (n-bases) and acceptors (x-acids). ' High wnductivitj. in

these types of complexes is associated with crystal structures in which planar molecules

are packeû hce to fhce.' n overlap and charge transfer interaction b e ~ n molecules

cause the unpaired n-electrons to be part ially delocalized a10 ng these O w -dimensional

stacks. This means that these complexes can conciuct elecmcity in that direction Two

important mo iecules invo lved in this branch of chemistry are tetracyano p

quinodimethane (TCNQ) and tetrathiafiilvaiene (T'ïF) (see figure 1.1).

T m Q TTF

Figure 1.1: Diapms ofTCNQ and TïF

The single cyta is of these molecular metais bave certain ~roperiies~:

1. The crystal lattices consist of planar stacks of donors and acceptors.

2. The stacks theniselves must be partially cbarged, Le. consist of neutral a d

charged molecules.

3. The conductivity inthese stacks is one dimemional, Le. the conductivity is

highest dong the stacking axis.

The stacking pattern is also important in the conductivity of charge tramfer sahs.

There are two main types of stacking 4:

1. Mked stacks, where donon (D) and acceptors (A) stack altematively (i.e. D-

A-D- A-D- A)

2. Segregated stacks, where donors and acceptors stack separately (Le. DD-D-

D-D.. ., and A-A-A-A-A.. ..)

Compounds that are segregaîed stacks conduct much more efficiently than mixed

stacks. This is because in segregated stacks, the electrons are tess localized due to

efficient %-orbital overlap. Short interplanar distances (3.17 A for TCNQ and 2.4 i A for

TTF) are crucial to the design of molecular metals, because it d o w s for n-molecular

orbital interaction and leads to the formation of a band.' as dlusuated by figure 1.2.

Figure 1.2: Formation of energy bands in a solid baseci on the overlap of atomic orbitals6

J k h band is made up of electmnic nates and the energy of these States fom a

conhuous range.' When the energy gap betvlieen the valence band and conduction band

(see figure 1.3) is large, the material is considered to be an insuiator. In materials with

smailer band gaps, promotion of an electron nom the valence band to the conduction

band is possible. These materials are known as semiconductors. In metals, the valence

band is partidly nIled, where elecwns can move easily into unlimited higher unoccupied

leveis, ailowing for conduction. The highest occupied level is known as the Femii level.

Its electrons, and those close to this level have a major influence on the physical

In charge tramfer complexes, the bands are derived h m the HOMO fiom the

domr +es and the LUMO for the acceptor species. Conductivity increases in these

complexes as the teqmature decreases âue to the reduction in the vibration of the

atomic lanice, thus kreashg orbital overlap. This is the oppsite of the temperature

dependence of semiconductors. At lower temperatines, less energy is available to

promote electmn across the band gap.

Figure 13: Banci structure of solids.'

ûrganic molecules such as TCNQ and TT?? are not the ody molecules that act as

molecular metais. If a planar molecule within a x-stack is bound to a transition metal.

variations in its molecular properties can be intmduced by changing the nature of the I

interactions with the rnetal8 This can cause variations in the conductivity of the

moiecular metal, as long as these perturbations do aot affect the x stack. In the 1960'~~

Uiorganic complexes such as K $ P t ( ~ ] B r o . > . 3 H 2 0 showed one dimensional metal-üke

characteristics due to the overlap of the metal d: ~rbitals.~ Much effort bas been put h o

incorporatmg the structural featurrs of the organic metals into the ligands for metal

complexes. In 1986, a series of highty conducting copper0 DCNQI (N,N'-

dicyanoquhmediimine) salts were discovered (see figure 1 .4).1° The crystai structure

showed that the DCNQI molecules are arranged in stacks linked with tetrahedmlly

coordinated copper ions (see figure 1 S).

Figure 1.4: Diagram of DCNQI

Figure 1.5: Perspedive view of the crysial smichire of Cu(XXNQr)z (H-atom Shom)

The DCNQi miecuie is almost planar and the copper compound consists of

d o m hce-to-fàce siacks of DCNQI molecules. By looking at the crystal smrtine, the

conduction peth seems to be formed mainiy by overlapphg prr-orbitals of DCNQI. "

Conductioo h u g h the copper atoms is unlikely, due to the large Cu-Cu distance (388

pm vs. the Cu-Cu distance in copper metal, which is 256 pm). In 2-5-dimethyl-DCNQI,

the metallic conductivity was found to be caused by the mixture of carbon 2p, nitmgen 2p

and copper 3d rnolecular orbitah in the valence band."

wth the discovery of the properties of this DmQI complex, interest has grown

in other conjugated, pianar organic molecules which can x-stack as ligands. Other metal

complexes of DCNQI and of phenyl cyanamide anion ligands may show high

conductivity . l 3 Platinum(rr) terpyridine complexes of pheny lc yanamide or

dicyanamidobenzene ligands may also be incorporated as building blocks in molecular

wires and switches.

1 1 2 Intmduction to the Cbemistry of the Starting Materials

The stuciy of transition metal complexes may be important in the understanding of

electron tramfer processes, mixed valence complexes, and magnetic coupling

interactions, e d 4 Platinum(II) terpyridine corriplexes have been well studied, and this

section will descni som of the chemistry of this system

The inflemiility of terpyridine (trpy) as a Ligand can cause steric effects to be

severe in some metal complexes. Trpy is an interesting Ligand because it does mt d o w

for the regubr octahedral geometries ~ ( t ~ p ~ ) ~ ] " . ~ ~ BackboDdmg h m filled metal d-

orb* to empty antibonding orbitals of p h ligands such as bipyridine,

phenantbrohe and terpyiidine increases the stability of the metai complexes with these

ligandsi6 Phtinum (II) complexes of terpyridine are knom to be planar m~lecules

similar to other Ccovalent paliadnim and plaîinum salts." The c m structure of

palladium anaiopes confmm the square planar coo~dinarion. Figure 1.6 is the crystal

structure of ~d~l(trpy)]+.

Figure 1.6: Crystal structure of [PdCl(trpy)]' showing bond angles.

The s t . is square planar with the coordinated terpyridine acting as a

tridentate ligand. The empty coordination site is filled with a covdentiy bonded chlorine

atom." The crystai structure consists of essentially plana. molecules packed in iayers as

show in figure 1.7.

Figure 1.7: View of the crystal ss~cture of [PdCl(trpy)]' sho wing intermo lecular contact.

The distortion in the planarity of these complexes is ke ly due to the steric

limitations of the rerpyridine molecuie. This meam that there is some decrease in the

stabilization ewrgy aEorded by the delocalized x bondkg. l9 The distance between

palladium is about 3.4 A which is close to the normal Vander Waal's radius. The closest

distance between the palladium and the nitrogen of neighbouring mo lecules is 3.1 3 & 0.6

A less than the Vander Waal's radius, showhg that there is some interaction between the

two groups.

The crystal structure of a [(trpy)PtCI]' has also been determined.zO Figure 1.8 is

the ORTEP drawing of the structure which is similar to many diimine and tris-chelate

complexes of plathum. The plat inun-platinum bond in diimines arises fiom the overiap

of the 5d: and 6borbitals of the neighbouring metal centres. The central trpy nitrogen

and the phtinum are relatively close with a short bond length of 1.952(15) k The other

Pt-N bond distances are near to 2 k The nitrogen-platiaurn-nitrogen bond angles are ail

les than 90".

Figure 1.8: ORTEP crystai structure of mCI(trpy)]*

Figure 1.9 shows the two independent cations in the crystai lattice. The cations

form a continuous stack dong the x - d i ~ t i o ~ and show repeating s h m and long

platinum-plat hum interactions. Figure 1.9 A shows the short Pi-Pt bond, whose vector is

nearly perpendicular to the two square planes. Figure 1.9B displays the long Pt-Pt

distance. One of the piaîimun trpy uniis is shifted laterally. The Pt-Pt distance is longer,

but the apy-trpy interaction is esrentially the same as in figure 1.9A.

The ligand field strength strongly influences the Pt-Pt interaction and

stackiag. Strong field ligands destabïlke S Q and allow for more interaction with

stacking. Also, n-afceptor d domr ligands affect stacking. Afceptors decrease the

ekctron demity on the metal centre, lessenhg the repulsion and shortening the Pt-Pt

distance."

Figure 1.9: ORTEP drawings of the two types of cation-cation interactions dong the m(trpy)Cl]' chahs. Structure A has a shorter Pt-Pt disrances, while B has longer Pt-Pt distances.

Merent colours of the platinum terpyridine starting material can be explained

by variations in the stackmg arrangements of the plam cations.

The UV-vis spectmm of piatinum(n) terpyridiw complexes has been extensively

s~idied. An intense visible absorption in these complexes has been assigned to a spin-

aiiowed metal-to-ligand charge transfer @lL+CT) involving dn-orbital of platinum as the

donor orbital and the x*-orbitais of trpy as acceptors. As the a-electron donating ability

of the fourth coordinated ligand iucreases the removal of an electron fiom the dn-orbital

becoms easiex and comsponding bands move to bwer eargies The apparent

extinction coeEcient in the UV decreases with increases [(trpy)PCl]' concentration due

to the k t that the W absorption bands of the oligomcrs are broader than those of the

monornets. l9

1.13 Iatroduction to Meta1 Compkxes of the Phenylcyanamide Anion and the

Dicyanamidobenzene Dianioo

The study of the transition metal coordioation chemisîry of phenylcyanamide

systems is important as its idonnation may lead to the coiistninion of molecular

materialS.

The cyanamide functional group is a resooance stabilized t hree-atom R-system.

There are two pairs of non-bonding electrons that cm be delocalized in these systerns

(See figure 1. IO)." Resooance structure A will coordinate to the metal via the nitrile

lone pair, ifody o-bonding interactions to the terminal cyanamide nitrogen are

considered. This results in an ideal bond angle of 180". Resonance structure B will

l d to the ideai bond angle of 120". However, a mixture of the IWO resonance of A and

B resuhs in a bond angle between the two ext~ernes.?~ Resonance ~ ~ c t u r e B will be

favoured in cases of strongly electropositive metal ions and metal ions with strong x-

acceptor character. The bond angle in these cases will be close to 1 80°, to maximize

interaction with the electron pairs on the nitmgeus.

Free anionic cyanamide ligands are anticipated to be planar, ifthere are no steric

effects. This is easily explained by the strong interaction of the cyanamide group with

the phenyl ring? An interesthg property of the phenyl cyanamide ligamls is that the o

and n4omr properties can be adjusfed by changing the subnituents on the phenyt ring2'

In [(trpy)Pd(~12-peyd]' , the pcyd is in the same plane as the trpy. This is due to

the extra space avaiiable in the fourth coordination site and the iack of steric hindrance.

This is in CO- to the pI(dip)(2-Clpcyd)] wtnple~ where the phenylcyanamide is

forced out of the piane by the stericaiiy hindered ligard8 In most transition metal-pbenyl

cyanamide complexes plaaanty of the cyanamide ligand is retaioed, provided steric

hindrance is not a problem

X flbl

b 1 Figure 1.10: a) Resomnce stabilized pbenylcyanamide anion ligand. b) Orthogonal n- symmetry molecular orbitals resulting h m the debcaüzation of two non-bondhg electron pairs as in resooaece fom B. The size of the atomic orbitals approxirnate their contri'b&on to the molecular orbital-

Dinuclear metal systeins involving di ave been well investigated for their possible

role in molecular switchhg devices. The control of metadmetai coupling is very

important in the contml of signal ûansfer. Metal-metal c o u p l . in dinuclear rutbenium

complexes were shown to be sensitive to the nature of the outer-amrdiiiation sphere.=

Pailadium dinuclear dicyd complexes, such as [{(aW)Pd)pp-(Me2dicyd)]Cl have

aiso been syntheskd and cbaracterized by IR 'H NMR. UV and cyclic voltammetry. 26

Tbse complexes were sbown to have unusual electrochemïcal pmperties, uadergobg 2-

electron processes, unlike similar dinuclear ruthenium complex It was also f o d that

the substituents on the dicyd phenyl ring affect the l igd's n-domr properties.

1.2 Aims of this Tbesis

Referring to the figure 1.5, the m a l structure of Cu(DCNQb shows planarity

of the DCNQI molecules and the high colductivity through the partially empty rings of

this mo lecule is due to the segregated n-stac king. Lotetactions exist through the 2p of the

carbon and nitmgen and the 3d of copper. The proposal of this research depends on the

possibility of building similar systems by taking two copper atoms and using dicyd2-

instead of DCNQI as a bridging ligand. Also, the other three DCNQi ligands bonded to

each copper are repiaced by trpy, because trpy is a phnar ligand. At the sarne time,

platimun is used instead of copper, due to its square planar geometry. Th& the dinuclear

complex wiil be plariar and this should kilitate ir-stacking . The goal of this project is to

grow crystals which have conductive properties through x-stacking of dicyd2' molecules

when oxidized by dopiog wiih I1.

1. To synthesize and cbaracterize a senes of mononuclear terpyridineplatïnum(11)

p h e n y l c y d d e complexes:

2. To synthesize and characterize dinuclear terpyridinepLatinw

dicyanamidobenzene complexes:

3. To investigate the spectroscopie and structural properties of the above cornpiexes.

Chapter 2

ExperimenQl Section

2.1.1. Reagents for Ligand S ynthesis

Ammonium thiocyanate (97%, ACS Reagent, Aldrich), bemyl chionde (99%,

Reagent Grade, Aldrich), lead (II) acetate trihydrate (>99%, Aldrich), glacial acetic acid

(99.7%, Anachernia), triethylamine (TE4 >99%, Alfa Aesar), sodium hydroxide (Lab

Grade, Anachernia), thaliium O acetate (99.99%- Aldnc h), ammonium thiocyanate

(98%, Aldrich), aniline (99%, Aldnch), 2,5-dimethylaniiine (990?, Aldrich), 3 3 -

dimethyloxyanilme (99'!!. Aldrich), 1 ,bpknylenediamine (97%, Akirich), 3 3,-

dimethyl4,4-phenyienediamine (97%, Aldrich), 3,s-dichloro- l,4-pheny lewdiamine

(97%. Aldrich), Ferrocene (J.T. Baker Chernical Co., sublimed) aii have been used as

received.

2.1.2 Reagents for Cornplex S ynthesis

Potassium tetrachloroplatinate(II) (99.9% Pressure Chernical Co.), 236'2"-

terpyridine (98%, MC h), ammonium hexafluompbospke (>95%, Aldrich),

hy&ochioric acid (36.5-38.0%, Reagent Grade, hachernia) have been used *ut

fitrtiaer purification.

2.13 Compressed Gases

Nitrogen @OC Gases), argon (Ulrra hi& puntiy, BOC Gases).

2.2.1 Solvents of the S p h s i s

Ethanol (anhydrous, Commercial Alcoho k, hc.), methaool (La b Grade,

Aaac hemia; glass distilled before use), acetone (Lab Grade, Ariachernia, glass distilled

before use), diethyl ether (99%, anhydrous, Caledon Labs), acetonitrile (99.83 %, HPLC

Grade, Alâric h), dirnethy lformaniide (99.98%, Anac hemia), dimethy lsul fo xide (99 9%

m h , ACS Reagent. Anachernia), water (dinilled using an analpicai deionizer).

2.2.2 U.V. Solvent

Dimethylformamide (99.8% min, ACS Reagent, Anachernia).

22.3 NMR Solvent

Deutrated dimethyl sulphoxide (DM0 isotopes), dimethyGddsulphoxide (99.9

atom% D, CDN Isotopes), tetramethylsilane (~99.9?/0 NMR Grade, ACS Reagent,

Aidrich).

23.4 Cyclic Vot*uiimtry Electrolyte and Solvent

TetrabutylLunmanium hexafluorophosphate was made by combining aqumus

solutions of tetrabutylammonium bromide (99??, Aldrich) and ammonium

hexafluoropho sphate (>95%, Aldrich). The c d e salt was recrystallized fko m ethano 1

twice and dried under vacuum at 1 10°C ovemight. Dimethylformamide was purinesi by

Al2@ and distilled under vacuum and argon.

2.3 Syntheses of the Ligands

2.3.1 Thallium sdts of pheny l c y a d d e derivat ives

22.1.1 General Description

Benzoyl thiocyanate was prepared fiom the reaction of bentoyl chloride with

ammonium thiocyanate, in acetone. To this was added the aniline to form thiourea

derivative. This cornpoumi was desulphurised by a heavy metal sah such as lead (II)

acetate, resulting in the pheny lcyanamide anion whic h is protonated by acetic acid. The

general scheme of the reaction is shown on the foilowing page.

Scbeme 2.1

+ NH4 SCN

a C-NCS + N%Cb)

where R = H, Cl, CH3, or 0CH3

The neutral phenylcyanamide could be converted to its thailium sait. To get pure

product, the reaction conditions shodd be carefully controlled. A h , there is equiiiirium

between the dimer ad its anion monomer. As a resuit, when thallium acetate is

introduced, the equilihium will SM to the mommer anion to give thallium

phenylcyanamide as the p i p i t a t e .

Scheme 2.1 (cont)

23.12 Ligand Synthesis of phenylcyanamide and its derivatives

Thallium salt of phenylcyanamide anion [Tl(pcyd)]

Benzoylchloride (2.8 g, 20 mmol in 20 ml acetone) was added hpwise to a

boiiing sohdion of ammonium thiocyanate (1.5 g, 20 mmol) in 20 ml acetone.

Immediately, ammonium chioride precipitatd The -ion was &wed to reflux for 10

min. Met thab aniline (1.9 g, 20 mmol) in 20 ml of acetone was added dropwise to the

reaction mixture. Thni, the reaction was alluwed to reflux for one hour to give milln(

yellow soiution which was poured slowly hto 300 ml of distillecl water with vigorous

stirrïng. The yellowish precipitate (benzo yliliiourea) was filtemi by Buchner funne1 and

washed copiously with distillai water. The benzoyl thiourea was dissolved in 50 ml of

hot aqueous solution of sodium hydroxide and boiled for 5 min. The solution was cooled

to 60°C, and then 6.5 g (20 mmol) of lead acetate in 20 ml of distillecl water was added.

The reaction was maintiiined between 50-60°C for 5 min to give a deep blafk

precipitation of PbS. Then, PbS was filtered off to get clear solution ofphenyicyaaamide

anion which could be converted to thallium sah of tbe ligand by two methods:

Fust methoci:

The clear solution of phenylcyanamide anion was cooled in an ice bath. Then, 5

ml of ghcial acetic acid was added to give immediately a white precipitate which was

filterd and washed with distilled water. The yield of neutral of pkny lcyaaamide was

1.68 g (72%). The neutral phenyicyanamide (1.68 g, 14 mmol) was dissolved in 65 ml of

a boiling mixture of waterfacetow (1 : 1). Then, thallium acetate (6.5 g, 23.5 rnmol) in 65

ml of watedacetone (1 : 1) was slowiy added to main sohition Imnsediately, triethylamine

(1.9 g, 18.7 m l ) was added. The solution was dowed to &tain boiiing for one

more minute and then was cookd to RT. Whae needle crystals were f o d fkom the

cooled solution which were fihered, foilected and washed with water foilowed by

acetone. Th yield was 2.15 g (68.2%).

Second method:

Thallium acetate (5.3 g, 20.12 rnmol) in 50 ml of water was added slowly to the

clear solution of phenylcyanamide anion described above (2.4 g, 20 mmol). Then, the

solution was heated for 5 minutes. It was allowed to cool, and a white precipitate was

collected by Ntration, waskd with acetone and air dried. The yield was 1.60 g (72%).

Thallium salt of phenylcyannmide anion ?ï@cyd) , and thallium sait of 2,3-

dichlompheny lc yaoamide anion. Tl(2.3 -C12pcyd), were prepared by both methods.

However, thallium salt of 3,5-dimethylphenylcyanamide anion T1(3,5-Me2pcyd) and

thallium sah of 3,5-dimethoxyphenylcyanamide anion Tl(3,S-(Meûhpcyd) were

prepared by the fïrst method

2.3.2 Thallium sahs of 1,4Dicyanamido benzene Denvat ives

23.2.1 Generai Description

To prepare protonated dicyanamidotsemene, bemyl thiocyanate was reacted

with 1,4-phcny lenediamhe derivat ive with heating to tom thiourea derivative. This was

desuiphmisecl by metal salt such as lead (II) a c e w with gentle heating to get the

dicyanamide diaaion and was protooated by acetic acid to form white precipitation of

aeutrai of 1 ,Wcyanarnidebenzene (H2dcya). However, the temperature of the reaction

should be maintained d e r 80°C to pievent -ion

23.2.2 Ligand Synthesis of 1,4-dkyanamidobe1lzene anci its derivatives

Thallium sait of 2,5-dimethy l- 1 , 4 - c d T12(Mez-Dic yd)

Ammonium thiocyanate (6.4 g, 84.2 m l ) in 85 ml of acetone was heated to

boiling. Benzoyl chloride ( 1 1.8 g. 84.3 mmol) in 100 ml acetone was added to the

bo h g solut ion to give immediately a white precipitate of m C 1 . Then, 2,5-dimethy l-

1,4-phenylenediamine (4.6 g, 42.6 m l ) in 85 ml of acetow was added slowly. Mer

that, the mùbure was allowed to boil for 1 5 min. Then, the mixture was poured to 1 500

ml of distilied water with stimng. The white precipitation was fiitered off by Buchnet

fimuel and was washed with 150 ml of acetone, 150 ml of water and once more 150 ml

acetone. The pale yellow wet complex was air dried.

The complex (15.9 g, 34 rnmol) was dissolveci in 200 ml of hot aqueous solution

o f W H (18.4 g, 0.4 mol). The solution was boiled for 10 min. and then was cooieù to

70°C. Lead (II) acet;ite trihydrate (32.5 g, 85 mmoI) in 80 ml of water was added to the

solution with the temperature of the reaction kept between 60-70°C. A biack (PbS)

precipitate was filtered off by Buchner funnel. Then, the clear sohdion of 2,S-dimethyC

1.4-dicyanamidobe~lzene dianion was mled by an ice ûath and acidifiecl with glacial

acetic acid. The white precipitation of MM2Dicyd was fihered off and washed with

mer. Then, the product was allowed to dry ovemight

The mde pioduct was recrystailized by dissohring in minimum of hot acetone

and then addiog M e d wata u t i l it staited to precipitate. Tben, it was put in a fiidge

(5°C). Mer gome t h e the crystals were fihered off and washed with very cou

watedacetone (1 : 1). The yield was 3 -39 g (54%).

Aheraatively, the d e product was dissolved in hot minimum DMF and then

was Gltered (very deep blue solution in case of DM-HIDicyd and pink in case of DC-HÎ-

Dicyd). An equal v o h e of water was added to the filtrate, precipitating some product.

The mixture was placed in the Bidge overnight. T'he product was filtered and vacuum

dried. The yield was high (80-90%). The IR spectra for the produa denved by the two

tecrystallization methods were identical.

To convert 3,5-Me2Dicyd to its thaihum sait, there are two methods:

First method:

The neutral2,5dirnethyl-1,4-dicyanamidobenzene (2.15 g, 12 mmol) in 150 ml of

hot acetooitrile and the sohition was fikered. Thallium acetate (6.3 g, 24 m l ) was

added slowly. Triethy lamine (2.7 g, 26.5 m l ) was addeù. Then, the solution was

ailowed to set aside to cool to give yellow precipitate which was filtered off and washed

with water followed by acetow and dried. The yield was 5 g (7W).

Second method:

Thailium acetate (26.3 g, 100 mmol) which was dissohred in 25 ml of distilled

water whic h was added to the ckar solution of 2,S-dimethyi- 1 ,edicyanamido benzene

dianion (2.6 g, 14 mmol). The solution was boiied for 10 min and anci then cooled to RT.

The yeilow precipitate was f i k d off and washed with acetone and dried in air. Th

yield was 7.71 g (65%).

Scheme 2.2

2 NY, SCN

2 lï(Ac0) 2 AcOH I

2 -4.1 Chloro(terpyridine) plathum(II) chioride dihydrate [(txpy)Pt C1]C1.2Hr0

This complex was prepared by using the m e h d for the d o g o u s Pd

complexes.26 Potassium tetrachloroplatinate @) (4.14 g, 10 ml) was dissolved in 700

mi of deionized water. Terpyridine (2.87 g, 12 m o l ) was added to the solution which,

after 2 h of reflux, gave a colour change to yellow orange. The reaction was refluxed for

four days until a Pt mirror began to fonn on the round-bottomeci flask. The red solution

was filtered and the filtrate's volume was reduced to 20% (40 ml). The red precipitate

was filtered and washed with very CO ld water fo liowed by acetone. The yield was 75-

95%.

Scheme 2.3

The crude [(trpy)PtCqCl@ 2H20 (1.85 g, 3.7 m m l ) was dissolved in a minimum

of hot acetonitriie, f ï i t d and was cooled to m m tempaatiae, yieküng red crystals

which were fihered and wasbeû with acetoœ The yield was 1.7 g (92% fiom mde).

Chloro(trpy) platinum(n)chloride dihydrate must be converteci to the salt which is

more sohibie in mst nonqireous solvents such as PFs and CF3S@.

This complex was made by using the method descn'bed for the d o g o u s Pd

complexes? Chloro(terpy) platinum(n)chloride dihydrate (O. 85 g, 1.7 mmol) was

dissolveci in f OO ml of distilled water and was heated to 50°C. Then, ammonium

hexafluorophosphate (0.45 g, 2.8 mmol) was dissolved in 50 ml of distilled water. The

latter was added slowly to the Grst solution with vigorous stirring, forming a yellow

canary precipitate. The mixture was ailowed to stir for 30 min. The precipitate was

fltered off and washed with distilled water followed by acetone and dried in air

overnight. The yield of the d e was (0.96 g, 1.6 mmol), 93%.

Scheme 2.4

To recrystallize the crude of [(trpy)RC1]PF6, it was dissolved in minimum of

DMF solvent without heaîing. The solution was filterd and e k r was allowed to diffuse

into the sohitioa Yebw needle crystals were formed which were coUected by filtration

and wastied with ether and dried d e r vacuum.

This complex was made by using the metbod described for the anabgous Pd

complexes? Chioro(trpy) p l a i h u m 0 chloride dihydrate (1 -38 g, 2.8 mmol) was put in

three-necked fia& (25 ml) which mis put in oü (Si&) bath. Nltrogen gas was albwed to

flow through the flask. Thea cRflic acid (0.9 g, 5 -5 m l ) was added carefully and

slowly to the tlask with stirring and increasing the temperatlue to 100°C. Hydrochloride

gas evolved and was monitored by passing t through a silver nitrate solution (&CI $1.

More triflic acid (0.1 g, 0.7 mmoI) was added and the reaction continued overnight.

After cooling the r&on solution, ether was added to precipitate the complex which was

filtemi, washed with ether and air dried. The yield of the crude was 1.80 g (88%)

Scheme 2.5

The triflic(trpy) platinum(II) trifiate (1.8 g, 2.8 rmno1)was dissolved in 150 ml of

hot acetone, the solution was filtered a d was dowed to cool at RT. 150 ml of ether was

added to precipitate the complex which was filtered, was washed with ether and was air

dried ovemight. The yield was 1.52 g (75%).

An improved method for rnaking the starting material is to use pktinum(II)

chloride PtC12 and 1 00/o dimethy isulfox.de (DMSO) 1 : 1 water+xetonrmle as the soivent.

Using this methocl, the siarting materiai, [{trpy)PtCl]Cl*2H20, uui be prepared in a few

hours and in nearly quantitative

2.5 Syntheses of mononuclear complexes of Platmum

[(trpy)Pt pcyd ]PFs (0.2 g, 0.3 3 mmol) was dissolveci in 75 ml of aceto&.de,

which was heated to 50°C. Tlpcyd (0.1 1 g, 0.33 m o l ) was dissolved in 50 ml of

acetonitrile and was added to the fist solution Mer short the, the colour of the

mixture solution changed to redaange and a white precipitate fomied The reaction was

heated and stinred for a fkther 40 min, and then the solution was fihered. The volume of

the filtrate was reducec! to about 50%, and then ether was added to crash the complex

which was fihered and washed with ether.

Scheme 2.6

To recrystallize the crude of the complex, it was dissolved in minimum hot

acetonitrile and was mered- Ether was dowed to d i fhe into the clear solution for a

couple of dayq slowly crysialliPng the complex which was filtered, washed with eîher

and was vacuum dried overnight. The yield was 0.15 g (66%).

Eiementai -sis based upon [(trpy)Pt pcyd]pF6] (as CuH&FbPPt, FW490.5

1)

Calcd (%) CC, 38.27; H, 2.34; N, 10.14

Found (%) C, 38.2; H, 2.36; N, 10.33

This complex was prepared in a similar manner to the previous one. The

recrystallization of the m d e complex was done as before. The yield was 0.14 g (600/0).

Elemental analysis h e d upon [(trpy)Pt@Mpcyd)][PF6] as (CzJboNtFsPPt, FW=718.5

g b 1)

Calcd (%) C. 40.12; H, 2.8 1 ; N, 9.75

Found (%) C, 39.08; H, 2-91 ; N. 9.49

This complex was niade in similar minner to the previous one. The

recrystallization of the fnide was done as before. The yield was 0.20 g (80%).

Elewntal analysis based upon [(trpy)Pt Ckpcyd]pFs] (as CuHi&ClzFsPPt, FW=

759.34 g/mol)

Found (%) C, 34.89; H, 2.22; N, 9.36

This complex was made in similar manner to the previous one. The yield was

0.23 g (93%).

Elementai analy sis based upon [(trpy)Pt-(MeO)rp~yd] pF6] (as C24H20N5F602PPt)

Caicd (%) C, 38.41 ; H, 2.69; N, 9.33

Found (%) C, 38.54; H, 2.90; N, 9.61

2.6 Syntheses of dinuclear complexes of pktinurn

(T1)z Mezdicyd (0.25g, 0.42 mmol) was placed in a £iask and was degassed under

argon. In another flask [(trpy)PtCIjPF,~ (0.5 g, 9.82 mmol) was dissolved in DMF and

degasxd under argon This so1ution was tben transkrred to tk ligand flask. Initially,

the colour cbariged h m orange to dark green ami after one week became &rk blue with

a white precipitate. The solution was filtemi and the product was forced out of the

nhrate by the addition of e k .

Scheme 2.7

DMF [(trpy)Pt CI]Pb + Th PMdicyd] - Ar

{(trp~)Pt)Tri-(DM-dicyd)l(PF6)2 + 2 TICI (s)

The cade complex was dissolved in hot DMF and then was filtered. Ether was ailowed

to diffuse into the clear deep blue filtrate. Mer a couple &YS, the solution was filtered

to give crystalline deep blue complex which was vacuum dried overnight. The yield was

0.46 g (84%).

Elemental analysis based upon [{R(trpy) ]2(p-2,5-Medicyd)](PFo) (as

C4&Iai#itP2Pt2, FW= 1330.83 g / m ~ l )

2.63 [fPt(trpy)}2(ÿ2?5-Ci2dicyd)l(CFpso3h

[(Pt(~y))2(CF3S03)](CF3S@) (0.4 g, 0.55 m l ) was dissoived in 150 ml of

DMF and was degassed by argon. This solution was transfmed to a flask containhg

DC-HIdicyd (0.07 g, 0.3 1 mmol, excess) (de-). Then, TEA (0.45 ml) was injected

into the solution. Mer a short time, the colour of the soiution changeci to iight green and

then changecl to purple. The &on was allowed to continue under argon atmosphere

for couple days.

Scheme 2.8

DMF 2 [@PY )PtCF3 S03 1 [ CF3 SO, 1 + DC-H2dicyd - TEA, Ar

[{Pt(trpy)h(ri-DC-~cyd)l(CF3SW + 2 TICF3SO3 (s)

The recrystallization was done by dissolving the cmde of the complex in DMF

ami filtering. Then, tbe c h solution was diffusai by ether. After a couple of &YS, the

product was filtered, washed with ether and dried in vacuo ovemight. The yield was 0.16

g, (42%).

Ele mental analysis based upon [{Pt(îrpy) ) 2(p2,EC12dicyd) J (CF3 S03)z (as

c ~ 2 ~ ~ # 6 C & j s 2 P ~ Fw= 1379.9 -1)

2.7.1 hhred Spectroscopy (IR)

I M spectroscopy was executed on Bomm Michelson 120 Fî-IR as KBr

(oven dried ai 120°C) disks. The spectra were comcted for background air. Data were

analyseci by ushg Bomem Grams/386 version 3.04.

'H NMR spectra were obtained on a Bruka AMX-400 spectrometer at 300K by

using ultra-miperial grade PP 507 sample tubes (Wilmad) and were referenced TMS.

Samples were dissolved in 4-dimethyl dphoxide. U d y , 10 mg of the sample was

dissolved in 1 .O0 ml of &-DMSO

2.73 Electronic Absorption S pectrosco py

Electronic spectroscopy was performed on a Cary UV-Vis/NIR

spectrophotometer. The simples were disso lved in acetonitrile for mononuclear

complexes and DMF for dinuclear complexes. N o d y , 10-1 5 mg of the sample was

dissolved in 200 mi of the proper solvent. Matching quartz cells were w d and solvent

background correction (badine) was d e t d e d

2.7.4 Cyclic Vobmmeîry (CV)

Cyclic vohammetry was performed on a BAS CV-27 eiecîmchemistry system

online to a BAS X-Y recorder. The electrochemical cell was made up of a double-

jacketed glass container. The temperature was govemed by means of a Haake D8-G

refiigerated bath aod circulator @recision f0.02OC). The teflon cap of the cell has four

holes for a platmum di& work electrode, wire counter electrode, reference electrode

(silver vuire) and an argon gas d e t tube. Tetrabutyiammonium hexafiuoropbospbate

(TBAH) was dissolved m 15 ml of distilleci DMF. Each sample was prepared by

disso1ving 10-1 5 mg in the DMF solution. Ferrocene (EO = 0.665 V vs NHE) was used as

a interd refmence?'

The X-ray structure detennination was performed by Dr. G.P.A Yap at Ottawa

University. There were two X-ray structura where determined for single crystal of

[(try)Pt@cyd)]PFa and [(trpy)Pt DM-(pcyd)]PF6. Data were collected on a Bniker

SMART CCD diBadometer.

2 -7.6 EIemental Analyses (EA)

Elemental analyses of ail samples were performed by the ctiemistry depanment of

the University of Ottawa AU of the samples have been recrystailized and dned for

overnight.

Mononuclear Complexes of Phenylcyaoamide Ligands: Physid Characterization and Discussion

3.1 Infmred Spectrweopy of Mononuclear Corn pkxes of Plitinum

M k e d spectra of the four mononucleat complexes, as weU as the starting

materid, are show in Figures 3.1-3.5. AU complexes show the v(NCN) in the range of

2165-2194 cm*'. Compared to the fiee ligand, the v(NCN) is shifted to higher

wavelength by 66- 1 16 cm" (see Table 3.1). Similar swing is seen in the v(C=N) of

hard cations bound to nitriles."

The v(NCN) of [(tqy)Pt@cyd)](PF6) diffas fiom the O* mnonuciear

plat inum complexes, in that two are visible. This rnay suggests the presence of two

types of Pt-N bondhg in the cornplex: through the amaK and nibile nitrogen. It is

possible that due to the d l e r aeric hindrance of the phenylcyanamide ligand the Pt@)

can coordioate to the amine nitrogen as weii as to the preferred nitrile nitrogen This may

also be explained by the crystal packing. Two v(NCN) are also seen in the thallium sait

of the unnibstinied pkny lcyanamide anion.

4000 3500 3000 2500 2000 1500 1000

Wavenum ber (cm")

Figure 3.1: h h r e d spectnim of [(trpy)PtCI](PF6) (KBr disk)

1

i l

O 4000 3500 3000 2500 2000 1500 1 O00

Wavenum ber (cm-')

F i p n 3.2: I d k e d spectrum of [(trpy)Pt@cyd)](PFs) (KBr âisk)

O 4000 3500 3000 2500 2000 1500 1000

Wavenurn ber (cm-l)

Figure 33: Innared spectnim of [(trpy)Pt(3,5-Mezpcyd)](PF6) (KBr disk)

O 4000 3500 3000 2500 2000 1500 1000

Wavenumber (cm")

Figure 3.k hfcarcd sperrnmi of [(trpy)Pt(2,3-Chpcyd)](PFs) (ICBr di&)

O

4000 3500 3000 2500 2000 1500 t O00

Wavenum ber (cm")

Figure 3.5 : h f k e d spectnim of [(trpy)Pt(3,5-(MeOhpc yd] m) (KBr disk)

Table 3.1 IR Data for the Mononuclear Phenylcyanamide Complexes '

P C Y ~ anion (L) r

P C Y ~

3 J-Mhp~yd

3,4=c@yd

3 , 5-Me02pcyd

In cm". Ail spectra were obtamed as KBr d i s

Ti sait of Ligand

2078,2056

2099

2102

2084

Krr~~)ptLl(PFs)

2194,2154 1

2165

2192 1

2177

3.2 Protom NMR Spectmscopy of Mooonuciear Complexes of Piatiaum

The proton NMR spectra of the four mononuclear complexes were taken as a

second method of characterizaiion The spectra were taken in d6-DMSO and ali

assignments are tabulated in Table 3.2.

NCN-

NCN

NCN

Figure 3.6: Roton numbering schemes for mommclear complexes of piatinum

Tabk 33 'H NMR Spectroscopy Data for [(trpy)PtLr Complexes a

Figure 3.7: 400 MHz 'H NMR spectrum of [(trpy)PtC1](PF6) m 4-DMSO

L

Cl

F Y ~ L

3,5-dimethylpcyd

2,3-dichloropcyd

3.5-dimethoxypcyd

'Chernicd shifis are in ppm. Al1 NMR spectra were taken in d6-DMSO

pcyd QY

H4

6.90

6.54

7.10

6.09

H2

7.52

7.13

7.16

6.66

Hl0

8.60

8.02

, 8.01

H3

7.25

7.03

tI9

7.90

H5

8.60

H6

8.60

H7

8.74

8.59

' ~ 8

8.48

8.65

8.68

8.52 8.62

8.59

8.67

8.67 8.54

8.50

8.11

8.61

8.54

8.42

8.41

8.62

7.94

7.96

7.98 8.54

7.98 8.01

Figure 3.8: 400 MHz 'H NMR specmim of [(trpy)Pt@cyd)](PF6) in &- DMSO

Figun 3.10: 400 MHz 'H NMR spectnim of [(trpy)Pt(3,5-Me2pcyd)](Ph) in cl6-DMSO (=thy 1 p e w

Figure 3.11: 400 MHz 'H NMR spectnim of [(trpy)Pt(Chpcyd)](P&) i~ &-DMSO

Figure 3.12: 400 MHz 'H NMR spectrum of [(t~py)Pt((Meû)~pcyd)](P~) in d6-DMSO (terpyridine and pcyd peaks)

The 'H NMR spectra showed many similarities to those of [trpy(Pd)12'

phenylcyanamide mononuclear complexes taken by Zl~ang.~~ This is reasonable since

Zhaog's complexes resemble those of this study, mth the ody major difference king the

metal centre.

3.3 Ekehoaic Absorption Spectrwcopy of Mononucleer Complexes of Phtinum

The electronic spectra of the four mononuclear platinum complexes, as well as the

[(trpy)PtCl]' starhg material were generated in acetonitrüe solution and are show in

figures 3.14-3.1 8. AU spectral assignments are listed in Table 3.3.

In the range of 200-300 nm, the spectra show n-x* transitions of the aromitic trpy

ligand. Metal-to-Ligand charge transfer (MLCT) W s were seen in the range of 300-

350 na Another interesthg feature of the UV-vis spectra is the broad ligand-to-meta

charge tramfer (LMCT) baads that appear amund 370990 nm. The transitions are broad

and are not very intellse, b u s e the LMCT is synunetry forbidden However, the bond

between the Pt ard cyanamide group is bent with an angle o f 159.1-175.9°. This causes

sorne mixhg between the n* orbitais of the cyanamide and the a*cm2$l orbital of

platinum and results in a partially allowed LMCT transition. ( n e ) .

A dflerence in the LMCT energies was mted when the ligand loses some of its

donathg chactter. AU phenylcyanamides are donor ügamis. However, the donor

propaties of the cyanamide group can be duceci by the addition of electron

withdrawing substmKms on the p h y l ring, e.g. CL The chlorinateci pheuylcyaoamide,

shows a hi* energy LMCT wmpaited to the dimahyl phenylcyanamide, which bas

more doaating character. This can be explaid by the faa that the prrseiice of the Cl

substituents on the phenyl ring stabilizes the nd orbitals of the pcyd. This increases the

energy gap between the x i of the ligand and a* of the mtal and shows that the LMCT

a AU daia were recorded in 3.00 x 10" M C&CN soiution. Extinction coefficieÏits are in

energies can be modifÏed siniply by cbanging the donating nature of the ligand.

Table 3.3 W-vis Absorption Data for [(trpy)PtL]' Complexes a

parentheses. sh = shouider; br = broad

L

Cl

,

Pcyd

L

3,j-dimethylpcyd

2,3-dichloropcyd

,

3,5-dimethollypcyd

PX* (QY)

209 (38000)

255 (44000)

270 (33300) sh

280 (43800)

245 (86200)

277 (59000)

208 (50500)

250 (41000)

282 (36300)

208 (49400)

220 (42000) sh

248 (37500)

276 (42600)

21 6 (47200)

245 (36800) sh

280 (32000)

MLCT

303 (15700)

3 16 (16950) sh

332 (23900)

348 (1 3900)

307 (26500) sh

328 (27700)

342 (38900)

312(16400)sh

328 (1780)

343 (1 8000)

327 (1600)

340 (1 9200)

328 (15550)

342 (16550)

LMCT

387 (3500)

370 (5000) sh

390 (300) sh

490 (2000) br

370(3500)

390 (2700)

490 (2900) br

370 (3700) sh

390 (2500) sh

462 (3200) br

370 (3300) sh

390 (2300) sh

490 (2500) br

3 0 0 4 0 0 5 0 0 W a v e l e n g t h ( n m )

Figure 3.14: UV-vis absorption spectnim of [(upy)PtCl](PF6) in CH3CN (3 -00 x 1 O%-)

3 0 0 r o o 5 0 0

W a v a i r n g t h ( n m )

Figure 3.15: UV-vis absorption spectnim of [(trpy)Pt@cyd)](PF6) in CH3CN (3.00 x 10**hl)

Figure 3.16: UV-vis absorption spectrum of [(trpy)Pt(3,5-Me2pcyd)](Ph) in CH3CN (3.00 x 1 0 " ~ )

4 2 0 0 3 0 0 4 0 0 5 O 0 6 0 0 7 0 0

W a w e i c n g t n ( n m )

Figure 3.17: UV-vis absorption spectrum of [(trpy)Pt(Chpcyd)](PF6) in CH3CN (3.00 x 1 0 - * ~ )

i l 1

i I

l 7 1

2 0 0 4 0 0 6 0 0

W a v e k n g t h ( n m )

Figure 3.18: UV-vis absorption spectrurn of [(trpy)Pt(@kO)2pfyd)](Pb) in CH3CN (3.00 x 10%)

3.4 Cycüc Voltammet y of Mononuclear Complexes of Phtinurn

Cyclic voltammetry is an important technique that has been used to study

electrochemical reactions for many years. The effect of ligands on the redox potential of

the metal ion in inorganic complexes is one of the significant applications of cyclic

vo ltammetry. 'O

The electrochemical data for the five platinum complexes, including the starting

mated, are shown in Table 3.4 and the cyclic voltammgrams are presented in figures

3.1 9-3.24. The cyclic vo ltammetry experirnents were performed in distilled DMF u s i .

plat hum working and counter electmdes, a silver wire pseudo-electrode and

ferrocene/ferrocenium couple (0.665 V vs. N.H.E.) as an intemal reference.

The two major features of the cyclic vo!tammograms are the platinum (+2/+)

couple. with a range of -0.56 to -0.45 V, and the terpyridine (O/-) couple, with a range of -

1.14 to - 1 .O5 V. Since the oxidation of fmocene is a known one-electroa event, and the

concentraiion of ferrocew added was the same as diat of the complex added, cornparison

of current heights of this couple with the platinum and terpyridine couples lead to the

conclusion that these were also one-electron events. Ahhougb the peak currents of

ferrocene and platimun mmplex couples are very reversible, there is a lack of

quivalence between ferrocenium/fmocew peak currents and those of the one electron

redox couples of the plathm complexes. This codd be due to ermr in the addition of

the ferrocew and platinum complexes. Also, it could be related to the reversibility of

these waves. The ferrocene couples possess a more ideal reversible behaviour compared

to the p l a t h anci trpy couples and this wiU have the effect of narrowing the

vokammogram waves. All redox events of the five mononuclear plathum complexes

were reversible. Cyanamide ligand oxidation events sbouid also be visible on the cyclic

vokammograms but are not seen for these complexes. By varying the scan rate for the

platinum mononuclear complexes, it was found that the voltages of the redox couples

were independent of scan rate (see figure 3.21).

FC'IFC W / W trpy O/-

Tabie 3.4: Electrochemical Daia for Mononuclear Plaîinum Complexes '

1 -42 Volts vs. N.H.E. -1.59 Figuir 3-19: Cyclic Voltammogram of [(trpy)PtCI](PFs) in distilled DMF

Complex

[(aP~)ptcl]pF6

[ ( ~ Y ) ~ @ C Y ~ ) I P F ~

[(WY )Pt(3,s-Metpcyd) lPF6

[(WY )pt(2,3-Chp~yd)]ph

[(~~PY)~(~.~-(M~O)~~CY~)]PFS

'AU potentials are in volts vs. N.H.E. using fmocene as the internai reference (665 mV vs. N.H.E.). Measured ushg 3.6 mM solutions in distilled DMF at 25°C at a scan rate of 1 00mV/s. EIectrolyte used was 0.1 M tetrabutylammonium hexafluorophosphate.

Platinum couple

-0.56

-0.52

-0.5 1

-0.45

-0-5 1

7 v

Terpyridine couple (00

-1.14

-1 .O9

-1 .O5

- 1 .os

-1 .07

4 c a n Direction 14.5 mAkm

1.09 I

Volts vs. N.H.E -1.59 Figure 330: Cyclic Voltammogram of [(trpy)Pt(pcyd)](PF6) in âistilled Dh4F

1 I

1.12 Volts VS. N.H.E -1.87 Figure 3.21: Cyclic Voltanmiogtam of [(trpy)Pt(3,5-Me2pcyd)](PF6) in distilled DMF

F&F c WIR+ t ~ p y 01-

V +Scan Direction 14.5 mA/m

1 I

1.23 Volts VS. N.H.E -2.00 Figure 3.22: Cyclic Voltammogram of [(trpy)Pt(2,3-Clzpcyd)](PFs) in distiUed DMF

1 I 1.10 Volts VS. N.H.E -1.6 Figire 3.23: Cyclic Voîtammograni of [(trpy)Pt((Meû)lpcyd)](Ph) in distilleci DMF

P~?+IP~+ trpy 01- f t

0.05 Volts vs. N.H.E -11.60 Figure 3.24: Scan Rate Dependence Cyclic Voitammogram for

[(~y)R((Ma)2p~yd](pF6) in distilkd DMF

3.5 X-Ray Structure Determination

The X-ray crystallographic &ta for two complexes, [(ûpy)Pt@cyd)] pF6] and

[(trpy)Pt(2,4M@-pcyd)] [CF3S03] are given in tables 3 53.7 and 3.8-3.10, respectively.

The hall-and-stick diagram for [(trpy)Pt@cyd)][PFs] is shown in figure 3.25 and both the

ORTEP diagram for [(trpy)R(2,4Mez-pcyd) J[CF3S03] are show11 in figures 3 26- 3.28.

The Ml-and-stick unit ceIl diagram are shown in figures 3.29 and 3.30. The stereoviews

of [(trpy)Pt(2,4-M4-pcyd)] [CF3S03] are also displayed in figures 3.3 land 3.32.

3.5.1 X- ray S tractu re for [(trpy)Pt(pqd)] (PFsj

The residuals of this crystd structure are very high with the R for the significant

reflections king 0.1592. Furthermore, the goodaess of fit was very bad at 3.454

resulting in values of low confidence. Hae we see that the Metal-Ligand bond occurs via

the nitrile nitrogen of the phenylcyanamide ligand as has ben seen in simiiar stuclies

involving palladium complexes of this nature. The crystal structure of

[(trpy)Pt(pcyd)] [PF6] indicates that the coordination environment about the Pt(Q metai

ion is one of a distorted square p h geometry with four nitrogen donor atoms making

up the coordination sphere.

Due to the p r data rauhing fiom this crystal analysis, emphasis on bond

lengtbs and angles wiil not be mentioned, however, this structure does confïnn the results

obtained f?om elemental d y s i s . A more useful structure for elucidating the geometry

of this complex is that of [(trpy)Pt(2,4-Me2-pcyd)][CF3S03].

3.5.2 X-ny stmctu re for [(trpy)Pt(2,4-Merpeyd)] [CF3SOd

The residuals of this crystal stnicture are acceptable with the R for the significant

reflections being 0.0530 and the goodaess of fit king 1.034. When compareci to the

previous structure, we see that the Metal-Ligand bond occurs via the same nitrile aitrogen

to platinum bondkg mode. Subsquemly, the crystal structure of [(trpy)Pt(2,4-Mez-

pcyd)][CF3S03] indicaîes tbat the coordmation environment about the P t 0 metal ion is

one of a distorted square plauar geometry with four aibogen domr atoms making up the

coordination sphere.

One of the more interesting &tors of this structure -sis is the k t that there

are 3 unique geometries present in this one crystaL We see from figures 3.26,3.27 and

3.28 that the structures do mt appear very dissimilar however, wben closely examining

the bond length and angle &ta, we see some small variations in the coordination sphere

about the P t 0 ion. For exarnple, the Pt-cyairamide bond angle in the three different

structures varies fiom 159-175". Two thlligs, however, are for certain. First, the

geometry of the P t 0 ion remab distorted square plaaar in all k e e structures and

second, the phenyl ring of the phenylcyanamide ligand and the Pt-trpy complex are

coplanar in ali three stnictures.

C l o s examination of the ball-and-stick diagram of the unit cell shows how the

complexes "stack" with respect to one another. A dotted line suggests some degree of

interaction between the P i 0 ion and the nitrile nitrogen of the phenylcyanamide ligand.

However, the distance between these two moieties is of the order of 5.4 & inacating

very üttle, if any, interaction between them

Table 3.5: Crystal data and structure refinement for [(trpy)Pt(pcyd)] [PFs]

Paramter Vaiue

Empirical Formula Formula Weight Temperature Wavelength Space Group CeU Dimensions:

a (4 b (4 c (4 a (degrees) P (degrees) Y (degrees)

Volume (A') 2, Calculateci density Absorption Coefficient F (000) (elecnons) Crystal size 8 range for data collection L iiniting indices Reflections coiiected/unique Completeness to 0 = 20.99 Refïneement mthod Data I restraints / parameters Goodness of fit on F' Final R indices R indices (al1 data) Extinction coefficient Largest ciifference (peak and ho le)

6.662 -' 660 0.4 x 0.1 xO.1 mm 1.69 - 20.99 O

-9ShI9,-lO<kSfO,OIlS 12 2306 / 2306 (R(int) = 0.0000) 99.6% Full-matrix least-squares on F~ 2306 / O /142 3.454 Rl=û. 1592, wR2=û.4172 RI4.1714, wR2=0.4213 0.0 M(5) 12.570 and 4.002 k3

Figure 3-25 BalI-and-shck drawing for the cornpiex [(trpy)Pt(pc~d)lrF61

Table 3.6: Atomic coordinates' and equivalent isotropie displacement parametenb for [(trpy )Pt( pc~d!l PFGI

7611!2) 7870(17! 0490(50) 6170 (40) 7850(40) ?SOO (50) 7830 (40) 8080 (50) 6600 (SOI aioo(s0, 8770(50) 7200 (50) 6160 (60) 5830 (70) 5230 (70) 5380 (70) 6200 (60) 6820 (50) 7630 (60) 7960 (60) 8760(70) 9190(50) 8840 (SOI 9310 (70) 10120 (70) IO380 (60) 1840 (60) 9010 (60) 6650 (50) 7250 (63) 7440 (60) 6740 (60) 5970 (70) 5800 (60) 6380 (50)

Table 3.7: Bond lengths (A) and angles (deg) for [(rrpy)Pt(pcyd)][PF6]

C(66] -C(67) -C(68) C(66) -C(67)-C(71) C(68)-C(67)-C(71) C(69)-C(68)-C(67) C(70} -C(69)-C(68) C(70) -C(69) -C(72) C(68)-C(69)-C(72) C(69)-C(70)-C(65) 0(3!-S(1)-O(21 O ( 3 ) -S(l)-O(1) O(2)-S(1)-O(1) O(3)-S(l1-C(73) O ( 2 1 - S ( 1 ) -C(73) O(i)-S(1)-C(73) F ( 3 ) -C(73)-F(2) F(3) -C(73)-F(1) F ( 2 ) -C(73)-F(1) F(3) -C(73) -S(1) F(2) -C(73)-S(I) Fil) -C(73)-S(l1 O(5)-S(2) -O(6) O(5) -S(2) -0(4) O(6)-S(2)-O(4) O(5)-S(2)-C(74) O(6)-S(2)-C(74) 0 1 4 ) -S ( 2 ) -C(74) F(6) -C(74)-F(4) F(6)-C(74)-F(S) F(4) -C(74)-€(SI F ( 6 ) -C(74)-S(2) F(4) -C(74)-S(2) F ( 5 ) -C(74)-S(2) O I 8 ) -S ( 3 ) -0(9) O(8) -S (3)-O(7) O(9) -S (3) -0(7) O ( 8 ) -S (3) -C(75) O(9) -S (3) -C(75) O ( 7 ) -S (3)-C(75) F ( 7 ) -C(75) - F ( 8 ) F(7) -C(75) -F(9) F(8) -C(75) - F ( 9 ) F(7)-C(75) -S(3) F ( 8 ) -C (75)-S ( 3 ) F(9J -C(751 -S(3) F(9' ) -C(7S1)-F(6') F(9')-C(75')-F(7') F ( 8 ' ) -C{75')-F(7')

Symmetry transformations used to generate equivalent atoms:

S p e t r y transformations used ta generate e a u i v a l e n t atoms:

Tab k 3.8: Crystal data and structure refinement for [(tqy)Pt(2,4Me-pcyd)] [CF3S03]

Enipirical Fonnula C2fi83Ns03PR Formula Weight 722.61 Temperature 203(2) K Wavelength 0.71073 A Space Group Tricl&, Pl Cell Dimensions:

a (4 10.345(3) A b (4 15.524(4) A C (4 23.506(7) A a (degrees) 78.819(5)" P (delFees) 83.794(5)' Y (deti?ees) 8 1.834(6)'

volume (A3) 3653(2) A3 2, Calculateci density 6, 1.971 m m3 Absorption Coefficient 5.910 mm' v F (00) (electrons) 2100 Crystal size 0.05 x 0.1 x 0.2 mm 0 range for data collection 1.35 - 22.50 a

L imiting indices -81hS 11 , -161k~15 , -2461525 Reflections coflected/unque 15237 / 9427 (R(int) = 0.0621) Completmess to 8 = 20.99 98.7% Rehernent method Full-matrix least-squares on F~ Data / restraints / parameten 9427 / 224 /IO43 Gooâness of fit on F* 1 .O34 Final R indices R14.0530, wR2=0.1112 R indices (al1 data) R14.0751, w W . 1 1 4 9 Largest Merence (peak and hole) 2.480 and -2.307k3

Figure 3.26: ORTEP drawing for the complex [(rrpy)Pt(2,4-Me1-pcyd)][CF3SQ 1- The triflate ion has been removed for clarïty

Figure 3.27: ORTEP drawing for the cornplex [(m)R(2,4-Merp-d)][CF3SQ]- The tnff ate ion has been removed for clan-ty

Figure 328: ORTEP drawing for the cornplex [(trpy)P1(2,4-Me~-~yd)][CF3so3]- The m'fl ate ion has been removed for claity

Figu re 3.29: Unit-ce1 l d i a p m for the corn plex [(trpy)Pt(2?4-Me~-pcyd)] [CF3S03].

Figure 3.30: Unit-ce11 diagram for the cornplex [(trpy)Pt(2,4-Me2-pcyd) J[CF3S03]

69 Figu re 3 3 1 : Stereoview for the complex [(trpy)P1(2, 4-Me2-pcyd)][CF3 SOI ]

I

Figure 3.32: Stereoview for the corn plex [(trpy)Pt(2,4-Mez-pcyd) ][CF3SO3]

Table 3.9: Atomic coordinatesJ and equivalent isotropie displacement parametersb for [(trpy)Pt~~,~-Me2-pcyd)lfCF3s031

Table 3.10: Bond lengths (A) and angles (deg) for [(trpy)Pt(2,4-Mel-pcyd)] [CF3S0,]

1.363 ( 1 7 ) 1 . 4 7 , 8 ( 1 8 ) 1 . 3 8 3 ( 1 7 ) 1 . 3 9 8 (18) 1 .507 (17) 1.394(16) 1.354 (17) 1.543(17) i.419(18) !.351(19) 1.364 ( l ? ) 1 . 3 5 4 (16) 1.485(16) i.417(17) l.363{17) 1.380(18) 1.393(17) f -474 (17) 1.386(17) 1.411(19) 1.31(2) 1.359(18) 1-385(18) 1.415(17) 1.403(18) 1.384 (18) 1.516(17) 1.387 (13) 1.355 (17) 1.508(18) 1.355(18) 1.356 (19) 1.391 (19) 1.380(18) 1.477 (18) 1.381 (17) 1 .361 (19) 1.330(18) 1.386(18) 1.460(18) 1-396(18) 1-38 (2) 1- 38 12) 1.376(19) 1.386(18) 1.415 (19) 1-37 (2) 1.39(2) 1-52 ( 2 ) 1.42 (2) 1.374 (19) 1.48 (2) 1.429 (8) 1.421 ( 8 ) 1.457(8} 1 . 8 2 4 ( 1 2 ) 1.323(12)

1.307 (12) 1.310(12j L.415(9) 1.436 ( O ) 1.458(9) 1.839(13) 1.315i14) 1.310(13) 1.322(13) 1.377 (9) 1.413(8) 1.538(14) 1.774(16) 1.292(1?) 1.286(17) 1.303 ( 1 7 ) 1.302 (18) 1.307 (17) l.336(17)

179.0(5) 80.3(4)

100-O(¶) 81.2(4) 98.4 (5) 161.5 (5) 1 7 8 . 4 (5) 81.0(4) 98.4 ( 5 ) 80.4 (4) 100.2(5) 161.3(4) l78.l(S) 81.2(5)

100.2 (6) 82.6(4) 96.l(S) 163.7 (5) 122.0(12) 125.3 (10) 112.6(9) 120.2(11) 120.8 (9) 118.9(8) 118.4 (12) 126.9 (10) 114.6(9) 159.1 (il, 123.1 (12) 120.4 (Il) 124.9(9) 114.7(8) 125.1 (10) 116.8 ( 5 ) Il8.*(8) 117.2 (11) 128.5(10)

Dinuclear Complexes of Dicyanamidobenzew (dicyd2] Ligands: Physical Charaeterization and Discussion

4.1 Infrnred Spectmseopy of Diiuciear Complexes of Piatinam

b e d specaa of the two dinuciear complexes are sbown in Figures 4.1 and 4.2.

AU complexes show a single v(NCN) in the range of 21 14-2158 cm-'. Compared to the

fke dicyd2- ligand, the v(NCN) is shifted to higher wavelength by 21-58 cm" (see Table

4.1).

In similar work done by ~ h ~ " ' , a dinuclear palladium complex of Mezdicyd was

synthesized. The h h e d spectnmi of this complex showed two equally intense v(NCN)

stretches. [ { (trpy)Pt ) rpMe2dicyd](PF& and [{(trpy)Pt) 2-p-C12di~yd] (CF3S03)2 showed

single cyanamide stretches.

Tabk 4.1 IR Data for the Dhuclear IIicyd2- Complexes "

Complex v(NCN) cm-' Complex

~ e 2 d i c ~ d "

v(NCN) cm-'

2093

! O -

4000 3500 3000 2500 2000 1 500 1 O00

Figu re 4.1: b e d S pectrum of [ {(trpy)Pt p-Medcyd] (PF& (KBr disc)

4.2 Proton NMR Spectroscopy of DUociear Complexes of Piatinum

The proton NMR spectra of the two dinuciear complexes were taken as a second

method of chac&&ation. The spectra were taken in 4-DMSO using a 400MH.z NMR

spectrometer. The assignmenîs for the spectra are similat to those for the mononuclear

piatinum complexes (see table 4.2). Shce the position of the trpy resonances changes

very iittle for the dinuclear complexes compared to the mononuclear complexes, it cm be

concluded that their environments are very similas.

Table 4.2 'H NMR Spectroscopy Data for [ ( t r p y ) ~ t ~ ] ~ ~ + Ornplexes '

L

Me2dicyd

Clzdic yd

achemical shifts are in ppm. Al1 NMR spectra were taken in da-DMSO

dicyd

6.74

6.92

WY

HS

8.54

8.47

H9

7.96

7.94

Hl0

8.54

8.47

H8

8.48

8.36

H6

8.54

8.47

H7

8.64

8.58

Figure 4.3: 400 MHz 'H NMR spectm of [{(trpy)PtJz-p-Me&cyd](pF6h in &-DMSO (terpyridine peaks)

Figure 4.5: 400 MHz 'H NMR spectrum of [{(trpy)Pt}2-p-C12dicyd](CF3S03)2 in 4- DMSO

4 3 Eiectronic Absorption Spectmseopy of Dinuclear Comp bxes of Piatinum

The electronic spectra of the two dinuclear platinun complexes in distilled DMF

solution are shown in figures 4.54.6. AU spectral assignments are listed in table 4.2.

The non* transitions of the aromatic trpy ligand are obscured by the solvent cutoff of

DMF. Metal-to-Ligand charge transfer (MLCT) bands wae seen in the range of 335-400

nm. Also sem on the UV-Vis spectra is the broad Ligand-to-Metal charge transfer

(LMCT) bands that appear a r o d 537-580 n m These LMCT are considerably more

intense than those for the mononuclear compkxes, because there are two LMCT

chromophores per mole of complex

Tabk 4 3 UV-vis Absorption Data for [((trpy)~t)2-CI-~]2' Complexes a

b I

%l data were recurded in 3.00 x 10" M distilied DMF solution. Extinction coefficients are in brackets. sh = shoulder; br = broad

3 O O 4 0 0 5 0 0 6 0 0 7 0 0 8 0 O 9 0 0

W a v e l e n g t h ( n m )

Figure 4.6: W-vis absorption spectrum of [{(ttpy)Pt}r~-M~dicyd]~F~k in distilleci DMF (3.00 x ~V'M)

6 0 0 8 0 0

W a v e l e n g t h ( n m )

Figure 4.7: UV-vis abso tion spectm of [{(trpy)Pt)2-p-C12dicyd](CF3S03)2 in rP dist illed DMF (3 .O0 x 10 M)

4.4 Cyclic Voltammet y of Dinuclear Complexes of Platinum

The electrochemicd data for the two dinuclear platinum complexes are s h o w in

Table 4.3 and the cyclic voltammograms are presented in figures 4.7 and 4.10. The

cyclic voltamrnetry experiments were performed in distilled DMF using platinurn

working and counter electrodes, a silver wire pseudo-reference electrode and

ferrocene/ferrocenium couple (0.665 V vs. N.H.E.) as an interna1 reference.

The cyclic vo ltammetry of [{(trpy)Pt)2-p-Me2dicyd](PF6)2 and [ { (trpy)Pt) 2-p-

Chdicyd](CF3S03)2 was very difficult. In order to complete a cyclic voltammagram

without decomposition of the dinuclear cornplex, it was necesssary to use swi rates of

400 mV/s or more. The first cyclic voltammograins obtained for these complexes were

very messy (see figures 4.7 and 4.9). When P t 0 is reduced to P t 0 there is a possibihy

of disproportionation If these two species p(0) and Pt@)] ex&, the cyc lic

voltammogram will be very messy. Nevertheless, the cyclic voltammograms in figure

4.8 resemble that of mononuclear complexes (see figure 3. lg), even though they are not

very clean It can be suggested that the kst wave is the Pt@I)/Pt(I) reduction couple and

the second wave is the trpy reduction couple. In fàct, if this is mie, then the poor

reversibility that is seen may be due to the disproportionation reaction in which two Pt(?

are formed 60m the sarne complex and react to rnake Pt(0) and R(I1). These products

may deposit on the surface of the work electrode. AAer many scans and fiequent

cleaning of the electrodes, reproducible cyclic voltammograms were obtained (see figures

4.8 and 4.10).

The two major features of the cyclic voltamrnograms are the platinum (+2/+)

couple, with a range of -0.62 to -0.7 1 V, and the terpyridine (O/-) couple, with a range of

- 1.1 to - 1.3 V. Al1 redox events of the dinuclear platinum complexes appeared to be

somewhat reversible. In dinuclear complexes, it is sometimes possible to see two metai-

centred redox events. In the two dinuclear piatinum complexes presented, these events

are superimposed, so oniy one peak is visible.

Table 4.4: Electrochemical Data for Dïnuclear Platinum Complexes '

" Al1 potentials are in volts m. N.H.E. using ferrocene as the intenial re ference (665 mV VS..

N.H.E.). Measured using 3.6 mM solutions in distilled DMF at 25OC at a scan rate of 400mV/s. Electrolyte used was 0.1 M tetrabuty lamrnonium hexafluorophosphate

Ligand couples

M.58. M.26

Terpyrid ine couple (Or) -1.1

P

Complex

[ {(trpy)Pt ) 2-v-Me2dicy dl (PF6 h

Plat hum couple

-0.62

+ Scan Direction l I 1 .O0 Volts vs. N.H.E - 1 S O Figure 4.8: Qctic vohammogram of [{(trp~)Pi)~p-Mqdicyd](PF6)2 in distilled DMF

H.25 mA/cm t Scan direction I I 1.00 V O ~ S VS. N.H.E -1.50

Figure 4.9 : Cyclic vohammo- of [{(~)Pt)rp-M~di~yd](PF6h in distükd DMF

+ Scan direction I

1.20 Volts vs. NH.E I

-2.25

Figure 4.10 : Cyclic voiîammogram of [{(trpy)Pt)2-p-C1Zdkyd](CF3S03)t in distilled DMF

Fc'IFc Ptz'/pt' trpy O/-

T=O.SO W c m +- Scan direciion

I I

1.20 Volts vs. N-HE -2.25 Figure 4.11 : C yclic vo hammogram of [((trpy)Pt } rp-Cl~ddrydl(CF3S03h in distilleci DMF

Attempts to grow X-ray quality crystals of these two dinuclear platinum

complexes have been unsuccessfÙL Many attempts were made using ciBiirent solvents

such as dichlorometbane, dimethylsulfoxide, benzonit.de a d methoxyet)ranol Also,

many dflerent kinds of df i sed solvents such as water, acetone, ethawl ether, and ethyl

acetate at RT and 5°C were used. However, wne of îhese methods wceeded to give

proper crystals for X-ray structure.

Chapter 5

Summary and Future Work

nie fokwing mononuciear complexes have been made: [(trpy)Ptpcyd]PF6,

[(~y)PmM-~cydlPF6~ [(trpy )Pm-pcyd] PF6 [(Qy)PtDMO-pcyd]PF6 which are

characterizci by IR, UV, CV and X-ray. Importantly, the crystal structure of these

complexes is s h o w to be planar and this is suggests that perhaps the dinuclear

complexes are p l a m as welL Udortunately, we could wt grow crynals of the dinuclear

complexes to prove planar geometry. Unfiominately, there was not &cient time to

measure the cooductivity of dinuclear complexes, however, this will be done by Dr.

Crutchley in the near future.

Moreover, the seps are invoived in making the dmuclear complexes conductkig

assume that there is x-stacking in the crystal lattice through dicyd '- ligands. The dicyd '' ligands are a filled n system and overiapping filled x system are not going ro be

conducthg. They have to be partially oxidized in the same way as the copper DCNQI

system and this can ôe done by doping the powder with h. The progress of oxidation can

be monitored spectroscopically by watching the growth of the radical anion bands in the

visible spectnrm3'

The electrochemistry of the dinuclear complexes, [((trpy)PtJ2-p-

Mezdicyd](PF& and [{(trpy)Pt ) 2-p-Châicyd] (CF3S03)2, gave ambiguous c yclic

voltammograms, as seen in figures 4.7 and 4.9. This phenornenon requires fiirtiaer study

before definite conclusions can be d e .

This study also gave the resuhs that the substitution on the phenyl ring on both the

pcyd anion and dicyd dianion ligands aEected the ligand's n-donating properties. By

chaagmg the substituents, one can adjust the donor properties of the ligand and so adjust

the properties of the complex Future studies could involve the synthesis of other

dinuciear (trpy)R(?I) complexes of other dicyd derivatives to shidy their properties.

Also, the effect of the stenc buik of the counter ion on stacking crystal lanice could be

investigaîed

The purity of the complex plays a cruciai role in the chernical and physical

properties. For this reason, more effort and different techniques should be e q l o yed to

ensure the purification of the complexes.

References

1. Wudl F.;Acc Chem Res, . 1984, 1 7,227.

2. Torrance, J. B.;Acc Chem Res,. 1979, 12, 79.

3. Williams, J.M.; Beno, UA; Wang, H.H., Le- P.C. W.; Emge, T.J.; Geiser, U.; Carlson. KD.; Acc Chem Res.. 1985, 18,261.

4. Ferraro, J. R; William$ J. M Introduction to Synthetic Electncal Conductors, Academic Press, London, 198%

5. Cowan, D. O. and Wiygd, F. M. Chem. Eng. News., 1986,64(29), 28.

6. Epstein, A.J.; Miller, J.S. Sci Am.. 1980,24 l(4O,52.

7. Bryce, M.; Chem. Soc. Rev. 1991,20,355.

8. Zhang, W.; Bensimon, C.; Crutchley, R. J. Inorg. Chem 1993,32,5808.

9. Cassoux, P.; Vala.de, L.;Kobayashi, H; Kobayashi, A.; Clark, RA. and Underhiil, A. E.

Coord Chem. Rev., 1991, 1 10. 1 15.

10. Aumulier, A., Erù, P.; Klebe, G.; Himig, S.; S h w J.; Werner, H. Angew. Chem. Int. Ed. Engl.. 1986,25,740.

1 1. Kaîo, R Kobayasb, H., Kobayashi, A; Mori, T. ; Inokuchi, H. Chem. Len., 1987, 1579.

12. Schrneisser, D.; K.; Gopel, W.; Von Schutz, J. U.; Erk, P.; Hunig, S. Chem Phys. Len. 1998,148,423.

13. Kaîo, R Kobayashi, H., Kobayashi, A.; Mori, T. ; Imkuchi, H. Chem. W., 1987, 1579.

14. Palepes, S.;Garouf$ A.; Sletten, J.; Bakaibassis, E.; Plakataroras, G.; Katasamoou, E.; Hadjikh, N.; Inorg. Chim. Acta, 1997,261,93.

16 . Romo, R; Nasiasi, N.; Scolaro, L.; Phitim, M.; Albinati, A.; Macchioni, k Inorg.. Chem., 1998,37,5460.

17. Morgan, G.; Bursîaü, F. H. 1 Chem. Soc.,l937,1649.

18 . Intille, G.; Wuger, C.; Baker, W. J. Cryst. Mol. Strruit. 1973,3,47.

19. Day, V.; Glick, M.; Hoard, J J Am. Chem. Soc. 1968,90,4803.

20. Bailey, J. A.; HU, MG.; Marsh, R E.; Miskowski, V. M.; Schaefér, W.P.; Gray, H . B Inorg. Chem., 1995,34,4591.

21. Connick, W. B.; Marsh, R E.; Schaefer, W. P.; Gray, H. B. Inorg. Chem. 1997,36, 913.

22. ArewG.; Calogera, G.; Campagna, S.; Scolaro, L.; Ricewîo, V.; R o m , R Inorg. Chem. 1998.37.2763.

23. Cmtchley, R J. and Nakicki, M. L. Inorg. C h . 1989,28, 1955.

24. Cndchiey, R J.; Hynes, R; Gabe, E. Inorg. Chem. 1990,29,492 1 .

25. Naklicki, M L.; Crutchley, R J. J. Am. Chem. Soc. 1994, 116,6045.

26. Zhang, W. Master's Thesis, Carleton University, 1993. 27. Lowe, Cordon; Vilaivan, Tirayut; J. Chem. Resecirch. (S) 1996,386.

ZS.A)Clarke, R; Ford, P.; Inorg. Chem. 1970,9,227.B) Fou% R; For& P.; Inorg. Chem. 1972, 1 1,899.

30. Mabboa Gary, J. Chem-Ed 60,697 (1983).

3 1. Remmi, A.; Evans. C.; Crutchky, RJ. Inorg. Chem,, 1995,34.