Hydroboration and Hydrogenation of an Osmium–Carbon Triple Bond: Osmium Chemistry of a Bis-σ-Borane

The complex [OsHCl­(CPh)­(IPr)­(PiPr3)]­OTf (1; IPr = 1,3-bis­(2,6-diisopropylphenyl)­imidazolylidene, OTf = CF3SO3) replaces the chloride ligand with a hydroxo group to give [OsH­(OH)­(CPh)­(IPr)­(PiPr3)]­OTf (2), which undergoes hydroboration and hydrogenation of its metal–carbon triple bond. The hydroboration products depend upon the reagent used. Treatment of 2 with Na­[BH4] leads to the bis-σ-borane complex OsH2(η2:η2-H2BCH2Ph)­(IPr)­(PiPr3) (3), whereas pinacolborane (HBPin) affords the arene compound [Os­(η6-C6H5CH2Bpin)­H­(IPr)­(PiPr3)]­OTf (4). The hydrogenation of the triple bond of 2 occurs under 4 atm of H2 and yields the toluene derivative [Os­(η6-C6H5CH3)­H­(IPr)­(PiPr3)]­OTf (5).