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

Multimetallic cooperative binding of heteroallenes provides an attractive route to their activation, but the reduction of CS(2) 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 CS(2) 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(t)Bu)(3))(4)], 1, leads preferentially to the reductive disproportionation of CS(2) to K(2)CS(3) and CS. The crystal structure of the thiocarbonate intermediate complex [U(OSi(O(t)Bu(3)(4) (μ(3)-κ(2):κ(2):κ(2-)CS(3))K(2)(18c6)(2)], 2, isolated from the toluene reaction mixture has been determined. In contrast, the heterobimetallic complex [U(OSi(O(t)Bu(3)(4)K], 3, promotes preferentially the reductive dimerization of CS(2) to K(2)C(2)S(4) and K(2)C(3)S(5). The [K(2)C(2)S(4)(DMSO)(3)](n), 5, and [U(OSi(O(t)Bu)(3))(4)K(2)(C(3)S(5))](n), 6, polymeric compounds were isolated from this reaction and structurally characterized.