Crystal and molecular structures of [MCl(CPhCMe2)(η-C5H5)2](M = Zr or Hf) and [TiCl0.5 Br0.5(CPhCMe2)(η-C5H5)2]: an unusual π-interaction with the metals and molecular orbital calculations on model compounds

Abstract

The compounds [MCl(CPhCMe₂)(η-C₅H₅)₂](M = Zr or Hf) and [TiCl_0.5Br_0.5(CPhCMe₂)(η-C₅H₅)₂], whose structures have been determined by X-ray diffraction, all show a π-type of interaction between the phenyl ring and the metal. This is revealed by (i) the conformation of the alkenyl ligand, (ii) the small value of the angle M–C(1)–C(5), which is 100.3(3)° when M = Zr and 105.7(2)° when M = Ti, and (iii) the lengthening of the M–Cl bond, to 2.480(1)Å for M = Zr. A specific electronic effect is demonstrated by charge-iterated extended-Hückel calculations on related model systems.