The oxidative polymerisations of 2,6-dimethylphenol with copper-(1-methylimidazole) complexes as the catalyst precursor compounds in different solvents showed the catalysts to be extremely active when using acetonitrile. Acetonitrile can act as a labile ligand for copper and also prevent the catalyst to become poisoned due to hydrolysis. Addition of increasing amounts of water leads to a progressive deactivation of the catalyst.