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‴MCl 3 ] [Cp‴ = C 5 H 2 t Bu 3 ‐1,2,4; M = Zr ( 1 ), Hf ( 2 ), Ti ( 3 )] and [(Et 5 C 5 )ZrCl 3 ] ( 4 ). Complex 1 is converted into the mixed zirconocene dichlorides [Cp‴CpZrCl 2 ] ( 5 ), [Cp‴Cp‐ZrCl 2 ] ( 6 ), [Cp‴Cp″ZrCl 2 ] ( 7 ), [Cp‴Cp 4 ZrCl 2 ] ( 9 ) (Cp = C 5 H 5 , Cp* = C 5 Me 5 , Cp″ = C 5 H 3 t Bu 2 ‐1,3, Cp 4 = C 5 i Pr 4 H) and into the benzyl complexes [Cp‴Zr(PhCH 2 ) 2 Cl] ( 10 ) and [Cp‴Zr(PhCH 2 ) 3 ] ( 11 ). Variable‐temperature 1 H‐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.