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Two New Dinuclear Sterically Crowded Cu II Complexes as Catalyst Precursors for the Oxidative Coupling of 2,6‐Dimethylphenol
Author(s) -
Aromí Guillem,
Gamez Patrick,
Kooijman Huub,
Spek Anthony L.,
Driessen Willem L.,
Reedijk Jan
Publication year - 2003
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.200390181
Subject(s) - chemistry , steric effects , catalysis , imidazole , oxidative coupling of methane , crystallography , polymerization , polymer chemistry , electron paramagnetic resonance , photochemistry , stereochemistry , organic chemistry , polymer , nuclear magnetic resonance , physics
Abstract The molecular structure and spectroscopic properties of the first two bis(μ‐η 1 ‐nitrato)‐bridged, dinuclear Cu complexes containing 4,4′‐biimidazole ligands are presented. 1 H NMR, EPR, and UV/Vis spectroscopy indicate that their solid‐state structure is not retained in solution. Dioxygen uptake measurements show that the presence of a methyl group at the 2‐position of the imidazole rings leads to a dramatic increase of the rate of the catalytic polymerization of 2,6‐dimethylphenol. Detailed examination of the molecular structures of both catalyst precursors in the crystalline state suggests that this may either be caused by the difference in basicity of the biimidazole ligands or by a small but important steric effect of the 2‐Me groups affecting the coplanarity of equatorial Cu II ligands and the orientation of the axial nitrate ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)