Monoborane NHC Adducts in the Coordination Sphere of Transition Metals

Irradiation of various carbonyl complexes in the presence of 1,3-dimethylimidazol-2-ylideneborane (IMe·BH3) afforded the new borane complexes [CpMn(CO)2(η1-H3B−IMe)] and [M(CO)5(η1-H3B−IMe] (M = Cr, Mo, W). With the exception of [Mo(CO)5(η1-H3B−IMe], which was detected only in solution, the solid-state structures of all species were validated by single-crystal X-ray diffraction. The NHC−BH3 moiety was found to be coordinated to the metal center through a B−H−M three-center two-electron bond presumably without any B−M interaction. π-Back-donation from the metal center to the boron-containing ligand is most likely negligible.