Sn-centred icosahedral Rh carbonyl clusters: synthesis and structural characterization and 13C–{103Rh} HMQC NMR studies

Abstract

The reaction of [Rh₇(CO)₁₆]³⁻ with SnCl₂·2H₂O in a 1 : 1 molar ratio under N₂ results in the formation of the new heterometallic cluster, [Rh₁₂Sn(CO)₂₇]⁴⁻, in very high yield (ca. 86%). Further controlled additions of SnCl₂·2H₂O, or solutions of HCl, or [RhCl(COD)]₂, give [Rh₁₂(µ-Cl)₂Sn(CO)₂₃]⁴⁻. Similarly, addition of HBr to [Rh₁₂Sn(CO)₂₇]⁴⁻ gives the related cluster [Rh₁₂(µ-Br)₂Sn(CO)₂₃]⁴⁻. Notably, if the addition of SnCl₂·2H₂O to [Rh₁₂Sn(CO)₂₇]⁴⁻ is carried out under a CO atmosphere, the reaction takes a different course and leads to the formation of the new cluster, [Rh₁₂Sn(µ₃-RhCl)(CO)₂₇]⁴⁻. All the above clusters have been shown by single-crystal X-ray diffraction studies to have a metal framework based on an icosahedron, which is centred by the unique Sn atom. Their chemical reactivity and ¹³C–{¹⁰³Rh} HMQC NMR spectroscopic characterization are also reported.