Reactions of M(CH2Ph)(4) (M = Zr and Hf) with alpha-diimine ligands 1 at -78 degrees C selectively afford tribenzyl amido-imino complexes of zirconium 4 and hafnium 5, whose treatment with B(C6F5)(3) gave the corresponding cationic dibenzyl complexes 6 and 7 capable of polymerizing 1-hexene.