Fulvene to Cyclopentadienyl Conversion with Homoleptic Complexes of Zirconium and Hafnium

The reaction of 6,6-dimethylfulvene with M(CH 2 Ph) 4 (M = Zr, Hf) in benzene gives [η 5 -C 5 H 4 (CMe 2 CH 2 Ph)]M(CH 2 Ph) 3 ( 1, M = Zr; 2, M = Hf) without any observable byproducts. A similar reaction for M = Ti is not observed. The single-crystal X-ray study of 1 shows a three-legged piano-stool geometry with an η 2 -bound benzyl ligand. A second equivalent of 6,6-dimethylfulvene does not react with either 1 or 2 . The bulkier 6,6-diphenyfulvene only reacts cleanly with the more Lewis acidic Hf(CH 2 Ph) 4 to give [η 5 -C 5 H 4 (CPh 2 CH 2 Ph)]Hf(CH 2 Ph) 3 ( 3 ). Using the tetraamido complexes M(NMe 2 ) 4 and 6,6-dimethylfulvene, one obtains dimethylamine and [η 5 -C 5 H 4 (CMeCH 2 )]M(NMe 2 ) 3 ( 4 for M = Zr) in good yield. These products are formally derived from the deprotonation of a fulvene methyl group and subsequent coordination of the resulting 2-propenylcyclopentadienyl fragment. Reaction of 4 and 6,6-dimethylfulvene affords the bent metallocene [η 5 -C 5 H 4 (CMeCH 2 )] 2 Zr(NMe 2 ) 2 ( 5 ). Excess 8,8-dimethylbenzofulvene and M(NMe 2 ) 4 provides exclusively the product with only one coordinated indene.