New Zirconium Hydrocarbyl Bis(phosphoranimino) “Pincer” Carbene Complexes

Reaction of the bis(iminodi(phenyl)phosphorano)methanes CH2(Ph2PNR)2 (R = Ad 1, SiMe3 2) with Zr(CH2Ph)4 in toluene under mild conditions gave novel electronically unsaturated bis(hydrocarbyl) carbene complexes of the formula [Zr{C(Ph2PNR)2-κ 3 C,N,N ‘}(CH2Ph)2] (R = Ad 3, SiMe3 4) in high yields. The 13C NMR resonances for the metal-bound carbon (82.8 (3), 84.7 (4) ppm) are shifted upfield relative to the previously known group 4 carbene complexes. The crystal structure of 3 shows a short metal carbon link which is common to two fused four-membered rings which are almost coplanar. The rings are formed by chelation of the two pendant imine centers of the ligand. These complexes represent the first examples of hydrocarbylmetal carbene complexes of a group 4 metal.