Synthesis and Reactivity of Ruthenium(BINAP)(PPh₃)

Abstract

Ru(BINAP)(PPh3)HCl cleanly reacts with LiCH2TMS to give Ru(BINAP)(PPh3) (1) that has been fully characterized, including by X‐ray diffraction (BINAP and TMS stand for (2,2′‐bis(diphenylphosphi‐no)‐1,1′‐binaphthyl and trimethylsilyl respectively). In sharp contrast with other carbonyl‐free phosphine complexes of Ru(0), 1 demonstrates a strikingly high thermal stability and no propensity for intramolecular C–H activation (cyclometalation). Yet 1 coordinates acetonitrile and readily exchanges its PPh3 ligand with alkenes and dienes, thus behaving like a “masked” 16‐e Ru(0) species. Electron‐poor alkenes coordinate more readily than electron‐rich ones, which testifies for the nucleophilic character of the Ru(0)‐BINAP fragment. While being thermally stable, 1 is highly reactive and is capable of activating C–H and N–H bonds, and even of cleaving an inert N–Et bond. The combination of high reactivity and stability originates from the P,arene‐chelation by the BINAP ligand, i.e., the coordinated π‐arene stabilizes Ru(0) to prevent cyclometalation, yet it can slide upon substrate coordination, thereby enabling a variety of inert bond activation reactions to occur under mild conditions.