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].

Convenient synthesis of a new cyclopentadienyl ligand functionalized with a nitrile pendant substituent is reported. The ligand was utilized for the preparation of group 4 bent metallocene or half-sandwich complexes that were characterized by spectroscopic methods and/or by single-crystal X-ray diffraction analysis. The reactivity of selected titanocene derivative was further investigated by performing an alkylation and an attempted conversion to cationic complex with coordinated pendant arm.Figure optionsDownload as PowerPoint slideHighlights
► A new cyclopentadienyl ligand bearing a C≡N group in the pendant arm prepared.
► The ligand utilized in group 4 metal complexes, 5 characterized by X-ray diffraction.
► Titanocene dichloride with one pendant arm converted to the dimethyl derivative.
► Cationic species formed by abstracting Cl− or CH3− from the respective Ti complexes.