Cationic Group-IV pincer-type complexes for polymerization and hydroamination catalysis

Abstract

Neutral Zr^IV and Hf^IV dimethyl complexes stabilized by unsymmetrical dianionic {N,C,N′} pincer ligands have been prepared from their corresponding bis-amido complexes upon treatment with AlMe₃. Their structure consists of a central σ-bonded aryl donor group (C) capable of forming robust M–C bonds with the metal center, enforced by the synergic effect of both the coordination of peripheral donor groups (N) and the chelating rigid structure of the {N,C,N} ligand framework. Such a combination translates into systems having a unique balance between stability and reactivity. These Zr^IV and Hf^IV dimethyl complexes were converted in situ into cationic species [M^IV{N⁻,C⁻,N}Me][B(C₆F₅)₄] which are active catalysts for the room temperature (r.t.) intramolecular hydroamination/cyclization of primary and secondary aminoalkenes as well as for the high temperature ethylene–1-octene copolymerizations.