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Issue 10, 2014
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Controlling selectivity in the reductive activation of CO2 by mixed sandwich uranium(iii) complexes

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Abstract

The synthesis and molecular structures of a range of uranium(III) mixed sandwich complexes of the type [U(η8-C8H6(1,4-SiMe3)2)(η5-CpMe4R)] (R = Me, Et, iPr, tBu) and their reactivity towards CO2 are reported. The nature of the R group on the cyclopentadienyl ring in the former has a significant effect on the outcome of CO2 activation: when R = Me, the products are the bridging oxo complex {U[η8-C8H6(1,4-SiMe3)2](η5-CpMe5)}2(μ-O) and the bridging oxalate complex {U[η8-C8H6(1,4-SiMe3)2](η5-CpMe5)}2(μ-η22-C2O4); for R = Et or iPr, bridging carbonate {U[η8-C8H6(1,4-SiMe3)2](η5-CpMe4R)}2(μ-η12-CO3) and bridging oxalate complexes {U[η8-C8H6(1,4-SiMe3)2](η5-CpMe4R)}2(μ-η22-C2O4) are formed in both cases; and when R = tBu the sole product is the bridging carbonate complex {U[η8-C8H6(1,4-SiMe3)2](η5-CpMe4tBu)}2(μ-η12-CO3). Electrochemical studies on both the uranium(III) complexes and the dimeric uranium(IV) CO2 reduction products have been carried out and all exhibit quasi reversible redox processes; in particular, the similarities in the U(III)/U(IV) redox couples suggest that the selectivity in the outcome of CO2 reductive activation by these complexes is steric in origin rather than electronic. The latter conclusion is supported by a detailed computational DFT study on the potential mechanistic pathways for reduction of CO2 by this system.

Graphical abstract: Controlling selectivity in the reductive activation of CO2 by mixed sandwich uranium(iii) complexes

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Article information


Submitted
13 May 2014
Accepted
07 Jul 2014
First published
07 Jul 2014

Chem. Sci., 2014,5, 3777-3788
Article type
Edge Article
Author version available

Controlling selectivity in the reductive activation of CO2 by mixed sandwich uranium(III) complexes

N. Tsoureas, L. Castro, A. F. R. Kilpatrick, F. G. N. Cloke and L. Maron, Chem. Sci., 2014, 5, 3777
DOI: 10.1039/C4SC01401D

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