Chemistry of Transition-Metal Clusters with Mixed Sb/S Ligands: Evidence for a Terminal Sb=S Double Bond in Cp*3Rh3Sb2S5 (Cp* = C5Me5).

The reaction of [Cp2*Rh2Cl4] (Cp* = C5Me5) with a slight excess of K3SbS3 in boiling THF gave the neutral clusters [Cp4*Rh4S5] (1), [Cp3*Rh3Sb2S5] (2), and after salt metathesis [Cp3*Rh3SbSn]PF6 (3; n = 5 and 6). The structures of 1-3 are heterocubane clusters with Cp*Rh, S, and Sb vertices but with sulfur inserted into one (1 and 2) or two (3) edges. X-ray diffraction analysis of 2 additionally reveals a very shod Sb-S distance of 2.297(1) Å within the novel μ3-Sb2S4 ligand. Density functional theory calculation of the model compounds [SSbS]3-, [HSSbS]2-, and [HSSbH2S]0 provided strong evidence for the existence of a stable terminal Sb=S double bond in 2. [ABSTRACT FROM AUTHOR]