A route to small clusters: a twisted half-hexagram-shaped M4(OH)4 cluster and its capacity for hosting closed-shell metals

Abstract

By combining different oxidation states, coordination indices and bridging systems, it has been possible to obtain the structurally novel M₄(OH)₄ cluster core (M = transition metal) found in the organometallic compound (NBu₄)₂[Pt^IVPt^II₃(C₆Cl₅)₈(μ₂-OH)₂(μ₃-OH)₂] (1). The cluster is formed by two (μ₃-OH) and two (μ₂-OH) units that bond platinum atoms in different oxidation states. The cluster core geometry can best be described as a half-hexagram. Compound 1 is an excellent precursor for preparing heterometallic clusters since it can host d¹⁰ or s² Lewis-acid metal centers through Pt→M dative bonds, as demonstrated by its reaction with Ag(I) to produce the heterometallic [Ag₂Pt^IVPt^II₃(C₆Cl₅)₈(μ₂-OH)₂(μ₃-OH)₂] (2), which has four unbridged Pt–Ag bonds.