The versatility of the boronyl ligand in binuclear cyclopentadienylrhodium derivatives.

Abstract: Density functional theory predicts the chemistry of the binuclear cyclopentadienylrhodium boronyls Cp2Rh2(BO) n (n =4, 3, 2) derivatives to be considerably more complicated than that of the related cyclopentadienylrhodium carbonyls Cp2Rh2(CO) n owing to the greater variety of BO coordination modes in energetically competitive structures. In this connection, the Cp2Rh2(BO) n structures resemble to a certain extent the previously studied isoelectronic cyanide complexes Cp2Rh2(CN) n . All of the energetically low-lying Cp2Rh2(BO) n structures prefer coaxial geometries with terminal Cp rings and bridging BO groups. By considering the bridging BO groups as neutral ligands, both one-electron donor bridging μ-BO groups bonded to the Rh atoms exclusively through their B atoms and three-electron donor η2–μ-BO groups bonded to the Rh atoms through both their B and O atoms are found in low energy structures. The three-electron donor bridging η2-μ-BO groups exhibit longer B–O distances and lower ν(BO) frequencies than their one-electron donor bridging μ-BO counterparts. The thermodynamic stabilities predicted for the binuclear Cp2Rh2(BO) n derivatives suggest them as possible synthetic objectives. [Copyright &y& Elsevier]