Additive-controlled selective hydrosilylation of aryl alkenes catalyzed by bis(silylene) pincer nickel(ii) chloride

Abstract

A new bis(silylene) [SiCSi] pincer nickel(II) chloride 1, [(L)Ni(Cl)] (L = 1,3-((PhC(^tBuN)₂Si)(Et)N)₂C₆H₃), was synthesized by the reaction of the corresponding [SiCSi] pincer preligands LH with NiCl₂(DME). The experiments indicate that complex 1 can efficiently catalyze hydrosilylation of alkenes with the participation of different additives. When KO^tBu was used as an additive, the anti-Markovnikov products were obtained for both aryl alkenes and aliphatic alkenes. But in the case of nBuLi as an additive, the Markovnikov products were formed from aryl alkenes. Further study indicated that a complex containing a Ni–H bond may be the real catalyst when using nBuLi as an additive. The molecular structure of complex 1 was confirmed with the single crystal X-ray diffraction technique. To the best of our knowledge, this is the first example of alkene hydrosilylation catalyzed by a silylene nickel complex.