Nucleophilic reactivity of the multiply bonded carbon center in group 4-pincer bis(iminophosphorano)methanediide complexes

The bis(iminophosphorano)methanediide (carbene) complexes [MCl2{C(Ph2P=NSiM e3)(2)-kappa C,kappa(2)N,N'}] (M = Hf(1), Zr (2)) form Lewis acid-base addu cts with THF, nitriles, and isonitriles and undergo 1,2-addition reactions with amines, alcohols, and alkyl iodides and [2 + 2]-cycloaddition reaction s with heteroallenes. The halide complexes can be alkylated with lithium al kyl reagents without attach at the carbene center. All these reactions are consistent with high-valent metal alkylidene character.