Selectivity of attack on a Si–C(sp3) sigma bond coordinated to NiII

(PNP)Ni+ (as its ( BAr F 4 - salt) adds PhCN to Ni, but HX cleaves the Si–CH2 bond to form Ni[η2−(tBu2PCH2SiMe2)N(H)(SiMe2X)][η2–CH2tBu2P]+, for X = OMe, piperidyl, N(H)CH2Ph, N(H)Ph, morpholinyl. The diprotic reagent H2O gives (η2–tBu2PCH2SiMe2OSiMe2NH2)(η2–tBu2CH2P)Ni+. RCCH (R = Ph, SiMe3, tBu) reacts, through three detected intermediates, to form (tBu2PCH2SiMe2)N(H)(SiMe2CH2tBu2PCCR)Ni+, a product where one P has been oxidized and Ni reduced, each by two electrons. This shows the dominant influence on reactivity of Si–C bond activation by its unconventional donation to nickel in the structure of (PNP)Ni+.