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

The complex [OsHCl­(CPh)­(IPr)­(P^<i>i</i>Pr₃)]­OTf (<b>1</b>; IPr = 1,3-bis­(2,6-diisopropylphenyl)­imidazolylidene, OTf = CF₃SO₃) replaces the chloride ligand with a hydroxo group to give [OsH­(OH)­(CPh)­(IPr)­(P^<i>i</i>Pr₃)]­OTf (<b>2</b>), which undergoes hydroboration and hydrogenation of its metal–carbon triple bond. The hydroboration products depend upon the reagent used. Treatment of <b>2</b> with Na­[BH₄] leads to the bis-σ-borane complex OsH₂(η²:η²-H₂BCH₂Ph)­(IPr)­(P^<i>i</i>Pr₃) (<b>3</b>), whereas pinacolborane (HBPin) affords the arene compound [Os­(η⁶-C₆H₅CH₂Bpin)­H­(IPr)­(P^<i>i</i>Pr₃)]­OTf (<b>4</b>). The hydrogenation of the triple bond of <b>2</b> occurs under 4 atm of H₂ and yields the toluene derivative [Os­(η⁶-C₆H₅CH₃)­H­(IPr)­(P^<i>i</i>Pr₃)]­OTf (<b>5</b>)