Activation of carbon dioxide by new mixed sandwich uranium(III) complexes incorporating cyclooctatetraenyl and pyrrolide, phospholide, or arsolide ligands

Abstract

A series of uranium(iii) mixed-sandwich complexes of the type [U(COTTIPS2)(CpEMe4)] (CpEMe4 = EC4Me4, E is N, P or As, and COTTIPS2 = C8H6{1,4-SiiPr3}), featuring a heterocyclic five membered ring, have been synthesised and their X-ray crystal structures determined. The redox properties of these complexes have been assessed using cyclic voltammetry and the results compared to the purely carbocyclic mixed-sandwich analogues. The reactions of [U(COTTIPS2)(CpNMe4)] and [U(COTTIPS2)(CpPMe4)] with CO2 afford the structurally characterised carbamate and phosphacarbonate complexes [U(COTTIPS2)]2(μ-O)(μ-η1:η1-O2CEC4Me4)2 (E = N and P respectively), arising from CO2 reduction and insertion.