STRUCTURAL AND VOLTAMMETRIC STUDIES ON THE REDUCTION OF THE BIS(2,2'-BIPYRIDYL)PLATINUM(II) CATION IN APROTIC MEDIA

The reduction of the bis(2,2'-bipyridyl)platinum(II) cation, [Pt(bpy)( 2)](2+), in aprotic media has been studied electrochemically. Voltamme try at scan rates above 500 V s(-1) reveals three reversible reduction s at -1.14, -1.45, and -2.07 V versus the ferrocenium/ferrocene couple . The first of these couples shows only a moderately fast electron tra nsfer. At lower scan rate, e.g., 0.1 V s(-1), or on the time scale of an electrosynthesis, the product of the first one-electron reduction i s shown to be the previously unknown homoleptic platinum(I) dimeric ca tion (mu(2)-2,2'-bipyridyl)bis(2,2'-bipyridyl)bi, [Pt-2(bpy)(3)](2+), an X-ray crystal structure of which is presented along with 2-D NMR an d EXAFS results showing this is also the major species in solution. Th e formation of [Pt-2(bpy)(3)](2+) is shown by digital simulation of vo ltammetric results to be by a first-order process initiated by one-ele ctron reduction of [Pt(bpy)(2)](2+), and subsequent ligand loss before insertion into the Pt-N bond of another molecule of reduced monomer. Electrolysis in the absence of inert electrolyte is shown to be a viab le means of producing pure samples of the products of electrode reacti ons, even in cases where these are delicate or unstable.