Ruthenium Agostic (Phosphinoaryl)borane Complexes: Multinuclear Solid-State and Solution NMR, X-ray, and DFT Studies

The reactivity of the (o-phosphinophenyl)(amino)borane compound HB((NPr2)-Pr-i)C6H4(o-PPh2) prepared from Li(C6H4)PPh2 and HBCl((NPr2)-Pr-i) toward the bis(dihydrogen) complex RuH2(H-2)(2)(PCy3)(2) (1) was studied by a combination of DFT, X-ray, and multinuclear NMR techniques including solid-state NMR, a technique rarely employed in organometallic chemistry. The study showed that the complex RuH2{HB((NPr2)-Pr-i)C6H4(o-PPh2)}(PCy3)(2) (3), isolated in excellent yield as yellow crystals and characterized by X-ray diffraction, led in solution to PCy3 dissociation and formation of an unsaturated 16-electron complex RuH2{HB((NPr2)-Pr-i)C6H4(o-PPh2)}(PCy3) (4), with a hydride trans to a vacant site. In both cases, the (phosphinoaryl)(amino)borane acts as a bifunctional ligand through the phosphine moiety and a Ru-H-B interaction, thus featuring an agostic interaction.