"Activating Carbon Monoxide and Carbon Dioxide with Organometallic Uranium Complexes- Closing the...
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Transcript of "Activating Carbon Monoxide and Carbon Dioxide with Organometallic Uranium Complexes- Closing the...
"Activating Carbon Monoxide and Carbon Dioxide with Organometallic Uranium Complexes- Closing
the Carbon Cycle"
Geoff Geoff ClokeCloke
CPD Conference June 22nd 2012
The Carbon Cycle
• ~80 % of current global energy supply depends on fossil fuels
• End product of combustion is CO2
• Oil reserves are finite- peak oil will occur
Create C-C bonds and/or C-H bonds from CO or CO2
“Uncertainty in petroleum cost and supply demands that alternative sources of primary organic materials be developed. Carbon monoxide as a component of synthesis gas (H2 + CO) from coal and biomass will have a leading role in meeting these needs. ..........develop strategies that use CO as a two-carbon or larger building block to construct the organic materials needed for fuels and chemical manufacturing.”
Wayland, Science, 2006
Sandwiches!
CrFe
Wilkinson FischerFerrocene Dibenzenechromium
U
StreitweiserUranocene
U
CH3
CH3 CH3
CH3CH3
SiiPr3
SiiPr3
Mixed Sandwich
Why Uranium ??
E / volts
UIV/III: E½ = -2.18 V
UIV
SiiPr3
SiiPr3
Cl UIII
SiiPr3
SiiPr3 + Cl-+ e-
- e-
What to do with all the depleted uranium??!
U235 0.7%U238 99.3%5,404,000 tonnes!
Uranium(III)- highly reducing
Cyclisation of Carbon Monoxide
O. T. Summerscales, F. G. N. Cloke, P. B. Hitchcock, J. C. Green, and N. Hazari, Science, 2006, 311, 829.
U
SiiPr3
SiiPr31 bar CO, Et2O
-80oC to RTTHF
The Oxocarbons (CO)n2-
The Next One in the Series- Squarate
O. T. Summerscales, F. G. N. Cloke, P. B. Hitchcock, J. C. Green, and N. Hazari, J.Am.Chem. Soc, 2006, 128, 9602.
U
CH3
CH3
CH3CH3
iPr3Si
iPr3Si
CO, toluene,
-30C
CH3 removed
Carbon Dioxide Activation
U
CH3
CH3
CH3CH3
iPr3Si
iPr3Si
1 bar CO2, -30C
toluene,
2CO2 + 2 e- CO32- + CO
from U
+
A.S.P. Frey, O.T. Summerscales, F.G.N. Cloke, M.P. Coles, P.B. Hitchcock, Chem.Commun., 2009
Carbon Dioxide Activation 2
Nikos Tsoureas, unpublished results 2012
CO2+CO
N2
Coupling of Nitric Oxide and Carbon Monoxide
U
SiiPr3
SiiPr3 CO +NO, toluene-80oC to 25oC
+CO
U
iPr3Si
iPr3SiN. . +
NO
CO + NO CO2 + N2Heterogeneous Pt, Rh Catalyst
600-700oC
catalyst surface
O N N O> 6000C
catalyst surface
O N N OCO
CO
>2000C<3000C
A.S.P.Frey, F.G.N.Cloke,M.P.Coles, P.B.Hitchcock,Chem. Eur. J., 2010, 16, 9305.
“Methanol Synthesis”
CO/H2 MeOH
U
SiiPr3
SiiPr3CO + xs H2
toluene, -80oC to 25oC
A.S. P. Frey, F. G. N. Cloke, M. P. Coles, L. Maron, and T. Davin, Angew. Chem. Int. Ed. 2011, 50, 6881
The Future…..
reductively (2e)activated/coupled
productUIVUIV2 UIII small molecule(s)
e.g. CO, H2, CO2, etc
reductively activated/coupled
product2 electrons
Chemically?Electrochemically- controlled potential electrolysis?