Group 4 metallocene complexes with pendant nitrile groups

The preparation of a new functionalized cyclopentadienyl ligand bearing a nitrile pendant substituent, (C₅H₄CMe₂CH₂CN)^? is reported. The corresponding lithium salt of this ligand (1) was prepared by the reaction of in situ lithiated acetonitrile with 6,6-dimethylfulvene. The ligand was subsequently utilized for the synthesis of group 4 metal complexes [(η⁵–C₅H₄CMe₂CH₂CN)₂MCl₂] (M = Ti, 2; M = Zr, 3; M = Hf, 4), [(η⁵–C₅H₅) (η⁵–C₅H₄CMe₂CH₂CN)MCl₂] (M = Ti, 7; M = Zr, 8), and [(η⁵-C₅Me₅) (η⁵ C₅H₄CMe₂CH₂CN)₂ZrCl₂] (9). Alternative route to 2 comprised the preparation of half-sandwich complex [(η⁵–C₅H₄CMe₂CH₂CN)TiCl₃] (6). The prepared compounds were characterized by common spectroscopic methods and the solid state structures of complexes 2, 3, 4, 7, and 9 were determined by the single-crystal X-ray diffraction analysis. In addition, compound 7 was converted to the corresponding dimethyl derivative [(η⁵–C₅H₅) (η⁵–C₅H₄CMe₂CH₂CN)TiMe₂] (10) and also treated with the chloride anion abstractor Li[B(C₆F₅)₄] to generate the cationic complex with the coordinated nitrile group, as suggested by the NMR spectroscopy. A formation of yet another cationic complex was observed upon treating compound 10 with (Ph₃C)[B(C₆F₅)₄].