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(NiPr2)C6H4(o-PPh2) prepared from Li(C6H4)PPh2 and HBCl(NiPr2) toward the bis(dihydrogen) complex RuH2(H2)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(NiPr2)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(NiPr2)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.