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 [Cp*4Rh4S5] (1), [Cp*3Rh3Sb2S5] (2), and after salt metathesis [Cp*3Rh3SbSn]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 short 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.