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.