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((NBuAr)-Bu-t)][B-(C6F5)(4)] (2e', Ar = 3,5-C6H3(CH3)(2)) is reported, showing a sterically dependent Zr/N-pi interaction. Complexes 2 catalyze the hydrogenation of electron-rich olefins and alkynes under mild conditions (room temperature, 1.5 bar H-2). Complex 2e binds CO2, giving [Cp2Zr(CO2)((NBuAr)-Bu-t)](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.