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

The reaction of [Rh7(CO)16]3- with SnCl(2).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 SnCl(2).2H2O, or solutions of HCl, or [RhCl(COD)]2, give [Rh12(mu-Cl)2Sn(CO)23]4-. Similarly, addition of HBr to [Rh12Sn(CO)27]4- gives the related cluster [Rh12(mu-Br)2Sn(CO)23]4-. Notably, if the addition of SnCl(2).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(mu3-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.