Manganese complexes bearing the chelating phosphane–borane ligand H3B·dppm [dppm = bis(diphenylphosphanyl)methane] have been prepared. Addition of H3B·dppm to Mn(CO)5Br using Na[BArF4] as a halide-abstracting reagent affords [Mn(CO)3(η2-H3B·dppm)][BArF4] (1). This reacts with CO to open the bidentate borane to afford [Mn(CO)4(η1-H3B·dppm)][BArF4] (2) in which the borane is now bound in a monodentate manner. The CO addition is reversible, and placing 2 under vacuum (hours) regenerates 1 quantitatively, demonstrating that the chelating phosphane–boranes can act as hemilabile ligands. The complexes 1 and 2 have been fully characterised by NMR spectroscopy and X-ray crystallography.
Merle, N., Frost, C. G., Kociok-Kohn, G., Willis, M. C., & Weller, A. S. (2006). Chelating phosphane-boranes as hemilabile ligands - Synthesis of [Mn(CO)3(η2-H3B·dppin)][BArF4 ] and [Mn(CO)4(η1-H3B· dppm)][BArF4]. European Journal of Inorganic Chemistry, 2006(20), 4068-4073. https://doi.org/10.1002/ejic.200600526