CHM 491 Senior Seminar

Synthesis and Characterization of Bidentate Phosphoryl Ligands for the Chelation of f-block Metals

Jeremy Cunningham

Power Crisis

• Nuclear Power Plant: $2-6 Billion

• One Fuel Cycle: $40mil

• Coal: $0.3/kWh

• Oil: $0.2/kWh

• Nuclear: $0.08/kWh

• Main Reason: Nuclear Weapons

Images from: YaleClimateCommunications.org

Nuclear Power

•Provides 20% of energy in USA

•104 reactors in 31 states

•Cost of energy from nuclear is cheaper and more stable than from petroleum

•Nuclear power plants reduce the amount of greenhouse gases produced

Images from: http://www.world-nuclear.org

Nuclear Waste Storage

• Nuclear waste is projected to increase 30% over the next twenty years

• Some waste products will generate considerable heat as they decay, others will remain intensely radioactive for very long time periods

• 270,000 metric tons of high level radioactive waste has accumulated in 30 countries

Nuclear Waste: What is it?

The Royal Society Science Policy Centre Report 10/11, Oct 2011; ISBN 978-0-85403-891-6.

**it is this 1% of actinides that accounts for the long term radioactivity of the waste (103-106 years)**

lanthanides in this mixture interfere with transmutation of highly radioactive actinides

Other Uses for Lanthanides and Actinides

MRI Contrast Agents:

Nd:YAG Lasers

Batteries

Magnets

Metal Chelation: Defining Terms

• A complex is formed when a metal atom or ion, acting as a Lewis acid, bonds by accepting lone-pair electrons from ligands, acting as Lewis bases.

• A monodentate ligand attaches at a single coordination site of the central metal, a bidentate ligand at two sites, and a polydentate ligand at two or more sites.

• Coordination number represents the total number of points of attachment for a given metal atom or ion.

http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Coordination_Chemistry

Metal Chelation: HSAB Theory

Hard Acids: High Charge Small Atomic Radius Ex.) Ti4+, Cr3+, Cr6+

Soft Acids: large atomic/ionic radius Low Oxidation States Ex.) Pt2+, Pd2+, Ag+, Au+,

Hg2+

http://www.chem.latech.eduPearson, Ralph G. J. Chem. Sci., Vol. 117, No. 5, 2005, pp. 369–377

Hard Bases: High electronegativity Low Polarizability Ex.) OH–, F–, Cl–,

CH3COO–, CO32–

Soft Bases: Lower Electronegativity High Polarizability Ex.) R3P, SCN–, I–, CN–

http://www.chem.latech.edu/

http://www.chem.latech.edu/

Chelation with d-block Metals

• The transition elements are those which haveopen d-subshells

• Geometry is metal dependent

• Easier to Separate

faculty.uml.edu/ndeluca/84.334/topics/topic6.html

Metal Chelation: HSAB Theory

Hard Acids Ti4+, Cr3+, Cr6+

Soft Acids Pt2+, Pd2+, Ag+, Au+, Hg2+

Hard Bases OH–, F–, Cl–, NH3, CH3COO–, CO3

2–

Soft Bases R3P, SCN–, I–, CN–

Chelation of the Lanthanides

Lanthanides:

• bonding is more ionic (buried 4f-orbitals)

• common oxidation state is 3+ across the row

• ionic radii varies only 17 picometers from La3+ (103 pm) to Lu3+ (86 pm)

Chelation of the Actinides

Actinides:

• bonding is more covalent (5f orbital participation)

• Charges vary, ions and can have oxides

• U6+ Th4+ Pu4+ Am3+ Np5+ UO2

2+ PuO22+

• ionic radii similar as well (Th4+ = 105 pm; Np5+ = 101 pm; Tb3+ = 104 pm)

Separation of f-block metals Actinides:

• bonding is more covalent (5f orbital participation)

• Slightly larger than lanthanides with similar oxidation number

Lanthanides:

• bonding is more Ionic (buried 4f orbitals)

f-element coordination chemistry:

• Both are considered as hard acids, ligand interaction predominately determined by steric/electrostatic interactions.

Nuclear waste remediation

Kaminski, M. D.; Mertz, C. J.; et. al, J. Am. Chem. Soc. 2009, 131, 15705

The PUREX Process

• Herbert H. Anderson and Larned B. Asprey at the University of Chicago, as part of the Manhattan Project


The TRUEXProcess

• Developed in the 1980’s for the extraction of all minor actinides and lanthanides.


The DIAMEX Process

• Predecessor to the TRUEX Process

• More eco-friendly upon incineration


The SANEX Process

• Sulfur-based soft-donor extractants show selectivity towards An(III)

• Varying pH enhances selectivity and alters solubility properties


Nuclear waste remediation

D. Häussinger, J. Huang, S. Grzesiek Journal of the American Chemical Society 2009 131 (41), 14761-14767

Actinides Tend to coordinate best with

soft donor atoms (S/N)

Lanthanides Tend to coordinate best with

hard donor atoms.

The Biros Research Group

Previous WorkCis-1,2-bis(diphenylphosphino)

Ethylene Dioxide

(Cis-dppeO2)

Coordinates to all f-block metals

No cis-trans isomerization observed

Cis-1,2-bis(diphenylphosphino) Ethylene Disulfide

(Cis-dppeS2)

Coordinates relatively poorly to Lanthanides

Cis-trans isomerization

P.T. Morse et al., Polyhedron (2015), http://dx.doi.org/10.1016/j.poly.2015.05.016

Paul Morse Brian Rawls

Our Approach

Conjugated, rigid bridge ligand

Large Atomic Radius; greater electron dispersion, softer ligand

Longer bond length with a stronger dipole moment


Goals

Synthesize the selenide derivative of cis-dppe

Form complexes with f-block metals

Study the extraction efficiency of cis-dppeSe2


Se

Se

Previous Extraction Data

Characterization Methods: Phosphorus-31 NMR

• 31P has an isotopic abundance of 100%

• The 31P nucleus also has a spin of ½, making spectra relatively easy to interpret.

X-Ray Crystallography•Bruker Diffractometer•Olex2

•Atomic Resolution

Characterization Methods:X-Ray Crystallography

X-Ray Crystallography•Bruker Diffractometer•Olex2

•Atomic Resolution

Characterization Methods:X-Ray Crystallography

SUMMER 2014

Trans-dppeSe2 observed (δP=Se:29.6ppm)

• Reaction occurred at reflux (65ºC) for 20 hours

• Red powder observed upon work-up

+KSeCN

THF

Preparation of cis-1,2-bis(diphenylphosphoryl)Ethylene Diselenide

• Concentrated reaction conditions (0.13M)

• Under nitrogen

• Stirred at room temperature for 4 hours

+2Se(s)

Toluene

31PNMR of reaction mixture• Three visible

products.

• Oxidized phosphorus: δ=(+)ppm

Cis-1,2-bis(diphenylphosphoryl)Ethylene Monoselenide

δP:= -27.5ppm(d)

3JP-P= 22.5Hz

δP=Se=+22.2ppm(d)

1JSe-P= 1258Hz

Trans-1,2-bis(diphenylphosphoryl)Ethylene Diselenide

δP=Se=+29.6ppm(s)

1JSe-P=695Hz, 815Hz

Z. Phasha, S. Makhoba, A. Muller, Acta Crystallographica E 68 (2012)

Cis-1,2-bis(diphenylphosphoryl)Ethylene Diselenide

• After Benzene Recrystallization

δ: +23.7ppm(s)1JP=Se= 737.1Hz

ppm

X-Ray Crystal Structure

P=O: 1.50Å P=S: 1.95Å P=Se: 2.10Å

Phosphorus-Chalcogenide Bond Character

• Strong dipole, weak bond strength

• Unobservable on IR

• P to Se σ bond determines bond energy

Bond

Dipole Moment

(D)IR(cm-

1)

31PNMR

(ppm)P=O 4.51* 1173 21.6

P=S 4.88* 637 32.3P=S

e 5.17* 561* 23.7

P.T.Morse Th(IV) complexes with cis-ethylenebis(diphenylphosphine oxide): X-ray structures and NMR solution studies Polyhedron*Kenneth B. Capps,Bodo Wixmerten,Andreas Bauer, and, and Carl D. Hoff Inorganic Chemistry 1998 37, 2861-2864

Phosphorus-Chalcogenide Bond Character

• Strong dipole, weak bond strength

• Unobservable on IR

• P to Se σ bond determines bond energy

• Observed dissociation of Selenium

Bond

Dipole Moment

(D)IR(cm-

1)

31PNMR

(ppm)P=O 4.51* 1173 21.6

P=S 4.88* 637 32.3P=S

e 5.17* 561* 23.7

P.T.Morse Th(IV) complexes with cis-ethylenebis(diphenylphosphine oxide): X-ray structures and NMR solution studies Polyhedron*Kenneth B. Capps,Bodo Wixmerten,Andreas Bauer, and, and Carl D. Hoff Inorganic Chemistry 1998 37, 2861-2864

Cis-Trans Isomerization

• Observed as sole product in KSeCN reaction• During attempted isolation via column

chromatography• Under heated reaction conditions• In very dilute solutions• After extraction studies

Cis-Trans: Aguiar & Daigle (1964)

Observations:

• Photoisomerization of cis-dppe failed.

• Benzene minimized isomerization

• Treatment trans-dppeS2 with acetic acid lead to trans-dppeO2

• Reflux in THF with PCl3 caused isomerization

A.M. Aguiar and D. Daigle, J. Am. Chem. Soc., 86, 2299 (1964)

,

Cis-Trans Thermal Isomerization

A.M. Aguiar and D. Daigle, J. Am. Chem. Soc., 86, 2299 (1964)Sigl, M., Schier, A. & Schmidbaur, H. Zeitschrift für Naturforschung B, 53(11), pp. 1301-1306 (2014).

Requires a strong lewis acid (such as PCl3)

MX3= AlBr3, GaBr3, InBr3

Cis-Trans Thermal Isomerization

Sigl, M., Schier, A. & Schmidbaur, H. Zeitschrift für Naturforschung B, 53(11), pp. 1301-1306 (2014).

Requires a strong lewis acid (such as PCl3)

Unoxidized phosphines. MX3=GaBr3, AlBr3, InBr3

Cis-Trans Photoisomerization

Janet B. Foley, Alice E. Bruce, and Mitchell R. M. Bruce Journal of the American Chemical Society 1995 117 (37), 9596-9597

Cis-Trans Photoisomerization

• π* character increases with atom softness

• Isomerization occurred within 3 mins by exposure to >300nm light

Janet B. Foley, Alice E. Bruce, and Mitchell R. M. Bruce Journal of the American Chemical Society 1995 117 (37), 9596-9597

Cis-Trans IsomerizationHνΔ

Cis-Trans IsomerizationHνΔ

δ- - - δ- - - δ- - δ- - δ- δ-

<< <

P=O: 1.50Å P=S: 1.95Å P=Se: 2.10Å

Extraction Procedure

• 1x10-4M An(III)/La(III) solution in 1M HNO3

• 3x10-4M cis-dppeSe2 solution in DCM.

Martin, K. A.; Horwitz, E. P.; Ferraro, J. R. Solvent Extr. Ion Exch. 1986, 4, 449; Stockmann, T.; Ding, Z. Analytical Chem. 2011, 83, 7542–7549.

Extraction Procedure

• 1x10-4M An(III)/La(III) solution in 1M HNO3

• 3x10-4M cis-dppeSe2 solution in DCM.

o 6.4x10-4M Arsenazo solution in Formic Acid Buffer (pH=2.9)

o λmax=655nm for Ln(III)

λmax=665nm for An(III)

Martin, K. A.; Horwitz, E. P.; Ferraro, J. R. Solvent Extr. Ion Exch. 1986, 4, 449; Stockmann, T.; Ding, Z. Analytical Chem. 2011, 83, 7542–7549.

Previous Extraction Efficiencies Cis-dppeO2

P.T.Morse Th(IV) complexes with cis-ethylenebis(diphenylphosphine oxide): X-ray structures and NMR solution studies Polyhedron

Previous Extraction Efficiencies Cis-dppeS2

Extraction Efficiency of cis-1,2-bis(diphenylphosphino) Ethylene Diselenide

Synthesis of cis-dppeSe1

• Reaction occurred in benzene

• The mixture was sonicated for 20mins before sitting for 3hrs

• ½ Equivalent of selenium, sit for 24 hours

• Methanol recrystallization

Characterization of Cis-dppeSe1

Crystal Structure 31P-NMR

• δP=Se=+22.2ppm(d)• 1JSe-P= 1258Hz

• δP:= -27.5ppm(d)• 3JP-P= 22.5Hz

Summer 2015

Cis-dppeS2: Platinum Complex

2

2

Future Work

Form more f-block metal complexes Preform more extraction studies Synthesize a new ligand

Acknowledgements and Funding Acknowledgements

Dr. Shannon Biros Dr. John Bender Dr. Richard Staples GVSU Chemistry Faculty

• Funding• National Science Foundation• GVSU: OURS

Dr. Richard StaplesMichigan State University

Dr. John BenderGrand Valley State University

Questions?