Reactions of the 6,6-dimethylcyclohexadienyl anion with MCl4(PMe3)2 complexes (M = Hf, Nb) – Isolation of complex intramolecular coupling products

Reactions of NbCl4(PMe3)2 and HfCl4(PMe3)2 with four equivalents of the 6,6-dimethylcyclohexadienyl anion lead to Nb(6,6-dmch)[η2,4-(dmch)2](PMe3) and Hf(6,6-dmch)[η3,4-(dmch)3](PMe3). Each complex has been crystallographically characterized, and found to contain one η5-bound 6,6-dmch ligand, with the other dmch units coupled together to yield olefin, allyl, and diene coordinations, resulting in 18 electron configurations for these compounds.