Reactivity of Silanes with ( tBu PONOP)Ruthenium Dichloride: Facile Synthesis of Chloro-Silyl Ruthenium Compounds and Formic Acid Decomposition.

The coordination oftBu PONOP (tBu PONOP=2,6-bis(ditert-butylphosphinito)pyridine) to different ruthenium starting materials, to generate (tBu PONOP)RuCl2 , was investigated. The resultant (tBu PONOP)RuCl2 reactivity with three different silanes was then investigated and contrasted dramatically with the reactivity of (iPr PONOP)RuCl2 (DMSO) (iPr PONOP=2,6-bis(diisopropylphosphinito)pyridine) with the same silanes. The 16-electron species (tBu PONOP)Ru(H)Cl was produced from the reaction of triethylsilane with (tBu PONOP)RuCl2 . Reactions of (tBu PONOP)RuCl2 with both phenylsilane or diphenylsilane afforded the 16-electron hydrido-silyl species (tBu PONOP)Ru(H)(PhSiCl2 ) and (tBu PONOP)Ru(H)(Ph2 SiCl), respectively. Reactions of all three of these complexes with silver triflate afforded the simple salt metathesis products of (tBu PONOP)Ru(H)(OTf), (tBu PONOP)Ru(H)(PhSiCl(OTf)), and (tBu PONOP)Ru(H)(Ph2 Si(OTf)). Formic acid dehydrogenation was performed in the presence of triethylamine (TEA), and each species proved competent for gas-pressure generation of CO2 and H2 . The hydride species (tBu PONOP)Ru(H)Cl, (tBu PONOP)Ru(H)(OTf), and (tBu PONOP)Ru(H)(PhSiCl2 ) exhibited faster catalytic activity than the other compounds tested.