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Titan‐, Zirconium‐ und Hafniumkomplexe mit 1,2,4‐Tri‐ tert ‐butylcyclopentadienyl‐Liganden
Author(s) -
Sitzmann Helmut,
Zhou Pu,
Wolmershäuser Gotthelf
Publication year - 1994
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19941270102
Subject(s) - chemistry , zirconium , steric effects , metallocene , ligand (biochemistry) , medicinal chemistry , stereochemistry , cyclopentadienyl complex , nuclear magnetic resonance spectroscopy , inorganic chemistry , catalysis , organic chemistry , biochemistry , receptor , polymerization , polymer
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.