Stretched σ-borane complexes of rhodium: A theoretical study

Structure and bonding in stretched σ-borane rhodium complexes [(η5-C5H5)Rh(HBpin)2] 1Rh and [(η5-C5H5)Rh(HBpin)(Bpin)2] 2Rh have been investigated. The optimized structure of 1Rh contains almost similar HBpin ligands. The B-H bond distances B1-H1, 1.696 Å and 1.747 Å in 1Rh and 1.686 Å in 2Rh are longer than expected for a single bond based on covalent radius predictions (1.19 Å) and those obtained by theoretical study for the free borane ligands (1.190 Å in HBpin). In 2Rh complex, less 2s character and more 2p character goes to the Rh-B2 and Rh-B3 bonds of boryl ligand than to the Rh-B1 bond of the borane ligand.