The formation of Cu (CsHsN):' species is shown by EPR to occur in the homogeneous phase oxidative coupIing reaction of phenylacetylene catalyzed by the 01 (CS HsP& (N03)2 complex. These species are observed for substrate to catalyst titios higher than 125. In recent years, several EPR studies have dealt with the investigation of copper-exchanged zeolites and the subsequent formation therein of copper complexes with ligands such as ammonia, pyridine, or unsaturated hydrocarbons [l--S]. In a discussion of the properties of the Cu(II)-pyridine complex stabilized in Y-zeolite, it was suggested by Turkevich et al. [ 1]
that "'it would be of interest to investigate the catalytic properties of this complex since the Cu(iI)-pyridine system has been reported to be a good catalyst for homogeneous oxidation [6J".
A large munber of papers has considered the EPR of nitrogen-bonded copper chelates, among which the Cu(CgHsN)p complex has receive'd particular attention [7], at least with respect to its eiectronic and geometric structures. Little attention was, however, paid to the investigation of its reactivity, Le., the pol;sibility to follow, by EPR changes in the coordination sphere of the Cu2+ ion in the course of a given reaction.
Herice, it was of interest to follow the behaviour of this complex du&ng a well&n&~ reaction,such as the . .