Titan‐, Zirconium‐ und Hafniumkomplexe mit 1,2,4‐Tri‐tert‐butylcyclopentadienyl‐Liganden

Titanium‐, Zirconium‐ and Hafnium Complexes with 1,2,4‐Tri‐tert‐butylcyclopentadienyl Ligands Lithium salts of easily available 1,3,5‐tri‐tert‐butylcyclopentadiene and 1,2,3,4,5‐pentaethylcyclopentadiene are used to synthesize the trichlorides [Cp‴MCl3] [Cp‴ = C5H2tBu3‐1,2,4; M = Zr (1), Hf (2), Ti (3)] and [(Et5C5)ZrCl3] (4). Complex 1 is converted into the mixed zirconocene dichlorides [Cp‴CpZrCl2] (5), [Cp‴Cp‐ZrCl2] (6), [Cp‴Cp″ZrCl2] (7), [Cp‴Cp4ZrCl2] (9) (Cp = C5H5, Cp* = C5Me5, Cp″ = C5H3tBu2‐1,3, Cp4 = C5iPr4H) and into the benzyl complexes [Cp‴Zr(PhCH2)2Cl] (10) and [Cp‴Zr(PhCH2)3] (11). Variable‐temperature 1H‐NMR spectra of 6–9 (8 is the Ti analogue of 7) indicated hindered oscillation of the Cp‴ ligand with ΔG≠ values between ≤8 kcal/mol (7, 9) and 13.2 kcal/mol (6). X‐ray structural analyses of complexes 7 and 9 reveal strong distortions owing to extreme steric congestion.