ON THE MECHANISM OF OXIDATIVE ELECTROPOLYMERIZATION AND FILM FORMATION FOR PHENANTHROLINE-CONTAINING COMPLEXES OF RUTHENIUM

New experiments involving electrochemistry, Auger spectroscopy and ele mental analysis of films and film-forming compounds, as well as X-ray crystallography and electrochemistry of a key model compound, have bee n used to elucidate the linkage structure and probable mechanism of fo rmation of oxidatively generated polymeric and copolymeric films of ph enanthroline-containing complexes of ruthenium. Film formation evident ly involves indirect electrochemical activation of coordinated 1,10-ph enanthroline to nucleophilic attack by the non-coordinated pyridyl nit rogen of a dipyridyl ligand singly coordinated to a second metal cente r. The resulting linkage is comprised of a carbon/nitrogen bond with a n excess positive charge residing on the nitrogen atom. Electrochemica l oxidation of a complexed metal ion (typically Ru(II)) drives the pol ymerization by: (a) rendering the 4 site of phenanthroline significant ly electrophilic, and (b) providing an oxidizing equivalent for eventu al H atom elimination and pyridinium ion formation via an internal ele ctron transfer sequence.