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

By combining different oxidation states, coordination indices and bridging systems, it has been possible to obtain the structurally novel M-4(OH)(4) cluster core (M = transition metal) found in the organometallic compound (NBu4)(2)[(PtPt3II)-Pt-IV(C6Cl5)(8)(mu(2)-OH)(2)(mu(3)-OH)(2)] (1). The cluster is formed by two (mu(3)-OH) and two (mu(2)-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 d(10) or s(2) Lewis-acid metal centers through Pt -> M dative bonds, as demonstrated by its reaction with Ag(I) to produce the heterometallic [(Ag2PtPt3II)-Pt-IV(C6Cl5)(8)(mu(2)-OH)(2)(mu(3)-OH)(2)] (2), which has four unbridged Pt-Ag bonds.