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–
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
Kaminski, M. D.; Mertz, C. J.; et. al, J. Am. Chem. Soc. 2009, 131, 15705
The TRUEXProcess
• Developed in the 1980’s for the extraction of all minor actinides and lanthanides.
Kaminski, M. D.; Mertz, C. J.; et. al, J. Am. Chem. Soc. 2009, 131, 15705
The DIAMEX Process
• Predecessor to the TRUEX Process
• More eco-friendly upon incineration
Kaminski, M. D.; Mertz, C. J.; et. al, J. Am. Chem. Soc. 2009, 131, 15705
The SANEX Process
• Sulfur-based soft-donor extractants show selectivity towards An(III)
• Varying pH enhances selectivity and alters solubility properties
Kaminski, M. D.; Mertz, C. J.; et. al, J. Am. Chem. Soc. 2009, 131, 15705
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
P.T. Morse et al., Polyhedron (2015), http://dx.doi.org/10.1016/j.poly.2015.05.016
Goals
Synthesize the selenide derivative of cis-dppe
Form complexes with f-block metals
Study the extraction efficiency of cis-dppeSe2
P.T. Morse et al., Polyhedron (2015), http://dx.doi.org/10.1016/j.poly.2015.05.016
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
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