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Formation and Activation of Zr/Hf Bis(phenolate‐ether) Precatalysts
Author(s) -
Cuthbert Eric N. T.,
Busico Vincenzo,
Herbert David E.,
Budzelaar Peter H. M.
Publication year - 2019
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201900716
Subject(s) - chemistry , cationic polymerization , ether , ligand (biochemistry) , catalysis , polymerization , stereoselectivity , stereochemistry , propene , polymer chemistry , medicinal chemistry , organic chemistry , polymer , biochemistry , receptor
Zr and Hf complexes of bis(phenolate‐ether) (“O4”) ligands feature high activity, stereoselectivity and molecular weight capability for propene polymerization at high temperature. Here we report a simplified ligand synthesis and several new examples of O4 ligands. The formation of precatalysts L MR 2 (M = Zr, Hf; R = Bn, Me) from L H 2 and MR 4 was found to be accompanied in some cases by the formation of dimers (µ‐L) 2 [MR 2 ] 2 , and X‐ray structures of two such dimers have been determined. Treatment of L MMe 2 with [Ph 3 C] + [B(C 6 F 5 ) 4 ] – produces fairly clean cationic species L MMe + which were studied by 1 H NMR. 2D ROESY data, in particular, suggest that for “smaller” O4 ligands the L MMe + cation reversibly rearranges from the active ( fac/fac ) form to a presumably inactive fac/mer or mer/mer form; more bulky substituents appear to suppress this rearrangement. Implications for polymerization catalysis are discussed.