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NSiMe3)2-κC,κ2N,N‘}] (M = Hf (1), Zr (2)) form Lewis acid−base adducts with THF, nitriles, and isonitriles and undergo 1,2-addition reactions with amines, alcohols, and alkyl iodides and [2 + 2]-cycloaddition reactions with heteroallenes. The halide complexes can be alkylated with lithium alkyl reagents without attack at the carbene center. All these reactions are consistent with high-valent metal alkylidene character.