Reductive disproportionation of carbon dioxide to carbonate and squarate products using a mixed-sandwich U(iii) complex

Abstract

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.

Mixed sandwich thorium complexes incorporating bis(tri-isopropylsilyl)cyclooctatetraenyl and pentamethylcyclopentadienyl ligands: synthesis, structure and reactivity

“…7 As a result of this superimposition, metrical parameters describing the carbonate unit cannot be reliably reported, however, the rest of the structure can be accurately described. 7 As a result of this superimposition, metrical parameters describing the carbonate unit cannot be reliably reported, however, the rest of the structure can be accurately described.…”

“…However, unlike uranium, access to the trivalent oxidation state of thorium is not straightforward. 6,7 Alternatively, the in situ reduction of a mixed sandwich Th(IV) halide precursor in the presence of a small molecule may produce a transient Th(III) intermediate, which could induce reductive transformations. [2][3][4][5] It was envisaged that the mixedsandwich ligand system consisting of dianionic COT TIPS2 (where COT TIPS2 = 1,4-{Si i Pr 3 } 2 C 8 H 6 ) and monoanionic Cp* ligands may provide sufficient steric and electronic stabilisation to isolate a Th(III) compound, which would be expected to display high reactivity towards CO or CO 2 in a manner similar to the analogous trivalent uranium system U(COT TIPS2 )-Cp*.…”

The reductive disproportionation of CO2 using a magnesium(i) complex: analogies with low valent f-block chemistry

“…2 The problem here is that such transformations typically require the cleavage, or partial cleavage, of one or both of the very strong O]C(O) bonds (532 kJ mol À1 ) of carbon dioxide. [10][11][12][13] To the best of our knowledge, there have been no studies on the reduction of CO 2 to CO using well dened s-block compounds. These can be stoichiometric or catalytic in nature, and while the lion's share of reductive CO 2 transformations require the involvement of d-block metal reagents, 2 examples enlisting p-and f-block element compounds are becoming more prevalent.…”

Mixed-sandwich complexes of zirconium(III) and hafnium(III): Potential analogues of [U(η-C8H6{Si Pr3-1,4}2)(η-Cp∗)] for cyclooligomerisation of CO

“…[Hf(h 8 -COT{Si i Pr 3 -1,4} 2 )Cl 2 ] 2 (4) This was prepared in an analogous manner to 1 from K 2 (COT {Si i Pr 3 -1,4} 2 ) (5.12 g, 10.36 mmol) and HfCl 4 (1.65 g, 5.19 mmol) before further addition of HfCl 4 (1.58 g, 4.98 mmol) to yield 4 as a pale yellow solid (4.01 g, 60%). 1 An ampoule was charged with 5 (1.66 g, 2.17 mmol), KC 8 (0.33 g, 2.41 mmol) and toluene (50 mL) added to yield a bronze-coloured suspension that was allowed to stir for 7 days to give a dark brown solution with black solids.…”

“…We have recently reported the reductive cyclooligomerisation of CO by mixed-sandwich U(III) complexes of the type [U(h-C 8 [4].…”