CS2 activation at uranium(iii) siloxide ate complexes: the effect of a Lewis acidic site

Abstract

Multimetallic cooperative binding of heteroallenes provides an attractive route to their activation, but the reduction of CS₂ at heterobimetallic sites, associating an electron-rich metal with a main group Lewis acid has not been explored. Here we show that the presence of a heterometallic U, K site plays an important role in the CS₂ reduction by uranium(III) complexes of the electron-rich and the sterically demanding tris(tert-butoxy)siloxide ligand. Specifically, the ion-pair complex [K(18c6)][U(OSi(O^tBu)₃)₄], 1, leads preferentially to the reductive disproportionation of CS₂ to K₂CS₃ and CS. The crystal structure of the thiocarbonate intermediate complex [U(OSi(O^tBu)₃)₄ (μ₃₋κ²:κ²:κ²⁻CS₃)K₂(18c6)₂], 3, isolated from the toluene reaction mixture has been determined. In contrast, the heterobimetallic complex [U(OSi(O^tBu)₃)₄K], 2, promotes preferentially the reductive dimerization of CS₂ to K₂C₂S₄ and K₂C₃S₅. The [K₂C₂S₄(DMSO)₃]_n, 5, and [U(OSi(O^tBu)₃)₄K₂(C₃S₅)]_n, 6, polymeric compounds were isolated from this reaction and structurally characterized.