ansa-Titanocene and -Zirconocene η2-Alkyne Complexes -Synthesis, Spectral Characteristics, and X-ray Crystal Structure

The reduction of the complex [(η5‐C5H4)‐ansa‐(η5‐C5H4)]TiCl2 with magnesium in the presence of Me3SiC2‐SiMe3 in THF at room temperature gives the ansa‐titanocone alkyne complex [(η5‐C5H4)‐ansa‐(η5‐C5H4)]Ti(η2‐Me3SiC2‐SiMe3) (ansa = Me2Si‐O‐SiMe2, 1). The similar pyridine‐stabilized zirconium complexes could be obtained by analogous reactions and addition of pyridine: [(η5‐C5H4)‐ansa‐(η5‐C5H4)]Zr(L)(η2‐Me3SiC2SiMe3) (ansa = Me2Si‐O‐SiMe2, L = pyridine: 2; ansa = SiMe2, L = pyridine: 3). All complexes were characterized by spectroscopic methods. An X‐ray structure determination of complex 3 was conducted, and the data were compared to those of the complexes rac‐(EB‐HI)Zr(L)(η2‐Me3SiC2SiMe3) [L = (S)‐(‐)‐nicotine: 6, EBHI = ethylenebis(tetrahydroindenyl)] and Cp2Zr(py)(Me3SiC2‐SiMe3).