Phosphido- and Amidozirconocene Cation-Based Frustrated Lewis Pair Chemistry

Methyl abstraction from neutral [Cp2ZrMe(ERR')] complexes 1 (E = N, P; R, R' = alkyl, aryl) with either B(C6F5)3 or [Ph3C][B(C6F5)4] results in the formation of [Cp2Zr(ERR')][X] complexes 2 (X(-) = MeB(C6F5)3(-), B(C6F5)4(-)). The X-ray structure of amido complexes [Cp2Zr(NPh2)][MeB(C6F5)3] (2d) and [Cp2Zr(N(t)BuAr)][B(C6F5)4] (2e', Ar = 3,5-C6H3(CH3)2) is reported, showing a sterically dependent Zr/N-π interaction. Complexes 2 catalyze the hydrogenation of electron-rich olefins and alkynes under mild conditions (room temperature, 1.5 bar H2). Complex 2e binds CO2, giving [Cp2Zr(CO2)(N(t)BuAr)]2[MeB(C6F5)3]2 (3e). Amido complex 2d reacts with benzaldehyde yielding [Cp2Zr(OCH2Ph)((OC)PhNPh2)][MeB(C6F5)3] (7d). Phosphido complex [Cp2Zr(PCy2)][MeB(C6F5)3] (2a) reacts with diphenylacetylene to yield frustrated Lewis pair [Cp2Zr(PhCCPh)(PCy2)][MeB(C6F5)3] (8a) which further reacts with a range of carbonyl substrates.