Preparation and properties of heterometallic cube derivatives Mo3M′S4 from [Mo3S4(H2O)9]4+ with M′ = Pt, Rh and Re, and [W3S4(H2O)9]4+ analogues

Abstract

Three heterometallic Mo3M′S4 derivatives (M′ = Pt, Rh, Re) of the incomplete single-metal depleted cube [Mo3S4(H2O)9]4+ have been prepared by reactions with [PtCl4]2− (+ H3PO2 reductant), RhCl3 and [Re(CO)5Br], respectively. With [PtCl4]2−, the initial product gives, on standing for 2–3 days, the edge-linked double cube [{Mo3PtS4(H2O)9}2]8+, which is difficult to elute in Dowex cation-exchange chromatography. In the reaction with RhCl3, chloro products, e.g. [Mo3RhCl3S4(H2O)9]4+, precede formation of [Mo3RhS4(H2O)12]7+, which is also difficult to elute, and with [Re(CO)5Br], the product [Mo3Re(CO)3S4(H2O)9]5+ is obtained. Analyses are consistent with oxidation state assignments Pt0, RhIII and ReI, where the reactions proceed by addition of these forms to [Mo3S4(H2O)9]4+. The analyses and X-ray crystal structure of (Mo2NH2)[Mo3Re(CO)3S4(NCS)4] are consistent with the formation of an Mo3ReS4 single cube. Yields are high in the first two cases, but much lower in the Re case. Alternative preparations are described in the case of Rh and Re. All three products decay on heating, with reformation of trinuclear [Mo3S4 (H2O)9]4+, which can be recovered by Dowex chromatography. As compared to heterometallic derivatives so far considered, those with M′ = Pt, Rh, Re are much more substitution (and redox) inert, and are air stable. Analogues from [W3S4(H2O)9]4+ with M′ = Pt, Rh have been prepared using similar procedures.