The stoichiometric reaction of 1 equiv of CO with [(U(eta-C8H6{SiiPr3-1,4}2)(eta-Cp*)] affords the linear diuranium ynediolate complex [(U(eta-C8H6{SiiPr3-1,4}2)(eta-Cp*)]2(mu-eta1:eta1-C2O2) which does not react with further CO to give the deltate derivative [(U(eta-C8H6{SiiPr3-1,4}2)(eta-Cp*)]2(mu-eta1:eta2-C3O3). Spectroscopic and computational studies suggest a plausible mechanism for the formation of the deltate complex, in which a "zig-zag" diuranium ynediolate species is the key intermediate.

The mixed-sandwich U(III) complexes [U(eta-C8H6{SiiPr(3)-1,4}2)(eta-CpR)(THF)] (R=Me5, Me4H) react with CO2 to give free CO and the U(IV) carbonate products [U(eta-C8H6{SiiPr(3)-1,4}2)(eta-CpR)]2(micro-eta1:eta2-CO3)]; the latter has been structurally characterised for R=Me4H; a 25% molar excess of the U(III) reductant gives a mixture of the carbonate and squarate [U(eta-C8H6{SiiPr(3)-1,4}2)(eta-C5Me4H)]2(micro-eta2:eta2-C4O4) products-the first synthesis of an oxocarbon from a CO2 carbon source.

A macrocyclic organosamarium(II) complex has been shown to provide the first example of the reductive disproportionation of carbon dioxide, giving a bimetallic carbonate complex and carbon monoxide in a facile reaction under ambient conditions.

Calculations reveal a multistep pathway towards formation of linear [U](2)-(μ-η(1):η(1)-C(2)O(2)); [U] = U(η-C(8)H(6){SiH(3)-1,4}(2))(η-Cp). However formation of deltate-bridged [U](2)-(μ-η(1):η(2)-C(3)O(3)) requires an alternative mechanism, involving a side-on [U](2)-(μ-η(2):η(2)-CO) complex and whereby the bridging units of [U](2)-(μ-η(2):η(2)-C(n)O(n)) intermediates (n = 1, 2) react directly with free CO.

Hydrogenation of CO: The reaction of [U(η‐C8H6{SiiPr3‐1,4}2)(η‐Cp*)] in toluene with CO and H2 at subambient to ambient temperature and pressure affords the methoxide complex [U(η‐C8H6{SiiPr3‐1,4}2)(η‐Cp*)OMe].