Heterometallic Mg-Ni-Mg Complex Promoted Hydrosilylation of Alkenes: Catalytic Performance and Intermediates Characterization

Abstract

Heteronuclear metal complexes have played an increasingly important role in both small molecules activation and catalytic transformation due to the potential metal-metal synergies. In this work, we reported that the well-defined Mg-Ni-Mg complex [( LMg) ₂Ni(C ₂H ₄) ₂] { L = [(DippNCMe) ₂CH] ⁻, Dipp = 2, 6- iPr ₂C ₆H ₃} was capable of catalyzing the conversion of a diverse array of terminal alkenes to hydrosilylated products in anti-Markovnikov fashion using PhSiH ₃ as the silicon source. The stoichiometric reaction of heterometallic Mg-Ni-Mg complex with one equivalent PhSiH ₃ obtained a silyl-nickel-monohydride complex [( LMg) ₂NiH(C ₂H ₄)(SiHPhEt)] featuring a Ni-Si-H-Mg interaction. Moreover, treatment of heterometallic Mg-Ni-Mg complex with three equivalents PhSiH ₃ provided the silyl-nickel-trihydride complex [( LMg) ₂NiH ₃(SiHPhEt)] with three hydride-bridged at Mg-Ni-Mg fragment. Further reactions of the resultant silyl-nickel complexes with alkenes, e.g., ethylene and styrene, yielded the corresponding alkene-coordinated Mg-Ni-Mg complexes [( LMg) ₂Ni(C ₂H ₄) ₂], [( LMg) ₂NiH ₂(C ₂H ₄)] and [( LMg) ₂NiH ₂(CH ₂CHPh)], respectively, with the elimination of PhEtSiH ₂. Based on the control experiments, both silyl-nickel-monohydride and silyl-nickel-trihydride complexes were considered as active intermediates in the catalytic hydrosilylation reaction.

Keywords

Heterometallic complex / Cooperative effect / Hydrosilylation / Magnesium / Nickel hydride

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