16- and 18-Electron Cp*Rh complexes with 1,2-dicarba- closo-dodecaborane(12)-1,2-dichalcogenolato ligands, as studied by multinuclear magnetic resonance

Abstract

The reaction of [Cp*RhCl 2] 2 1 with dilithium 1,2-dicarba- closo-dodecaborane(12)-1,2-dithiolate ( a) and -diselenolate ( b) afforded the 16-electron rhodium(III) half-sandwich complexes Cp*Rh[E 2C 2(B 10H 10)] [E=S ( 3a), Se ( 3b)]. The 18-electron trimethylphosphane rhodium(III) half-sandwiches Cp*Rh(PMe 3)[E 2C 2(B 10H 10)] 4a– c were prepared from the reaction of Cp*RhCl 2(PMe 3) 2 with the same dichalcogenolates, including the ditelluride ( c). The complexes 4a, b could also be obtained from the reaction of 3a, b with trimethylphosphane. The molecular geometry of 4b was determined by X-ray structural analysis. The 16-electron complexes 3 are monomeric in solution as shown by multinuclear magnetic resonance ( 1H-, 11B-, 13C-, 31P-, 77Se-, 103Rh-, 125Te-NMR), also in comparison with the data for the trimethylphosphane analogues 4a– c and for 6a in which the rhodium bears the η 5-1,3-C 5H 3C 5H 3 t Bu 2 ligand. The 103Rh nuclear shielding is reduced by 831 ppm ( 3a) and 1114 ppm ( 3b) with respect to the 18-electron complexes 4a, b. Similarly, the 77Se nuclear shielding in 3b is reduced by 676.4 ppm with respect to that in 4b.