Group-4 transition-metal boryl complexes: syntheses, structures, boron-metal bonding properties, and application as a polymerization catalyst.

Two group-4 boryl complexes, boryltitanium 2 and borylhafnium 3, were synthesized via nucleophilic borylation using boryllithium 1. Complexes 2 and 3 are the first examples of group-4 borylmetals. Theoretical calculations on model molecules 5 and 6 indicated that the boron-metal bond in both complexes has a covalent character. Complex 3 has activity for polymerization of ethylene or hex-1-ene.