Nonclassical β-Hydrogen Elimination of Hydrosilazido Zirconium Compounds via Direct Hydrogen Transfer

Salt metathesis reactions of Cp2(NR2)­ZrX
(X = Cl, I, OTf) and lithium hydrosilazides ultimately afford hydride
products Cp2(NR2)­ZrH that suggest unusual β-hydrogen
elimination processes. A likely intermediate in one of these reactions,
Cp2Zr­[N­(SiHMe2)t-Bu]­[N­(SiHMe2)2], is isolated under controlled synthetic conditions.
Addition of alkali metal salts to this zirconium hydrosilazide compound
produces the corresponding zirconium hydride. However as conditions
are varied, a number of other pathways are also accessible, including
C–H/Si–H dehydrocoupling, γ-abstraction of a CH,
and β-abstraction of a SiH. Our observations suggest that the
conversion of (hydrosilazido)­zirconocene to zirconium hydride and
silanimine does not follow the classical four-center mechanism for β-elimination.