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. Voltammetry at scan rates above 500 V s(-1) reveals three reversible reductions 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 transfer. 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 is shown to be the previously unknown homoleptic platinum(I) dimeric cation (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 and EXAFS results showing this is also the major species in solution. The formation of [Pt-2(bpy)(3)](2+) is shown by digital simulation of voltammetric results to be by a first-order process initiated by one-electron 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 viable means of producing pure samples of the products of electrode reactions, even in cases where these are delicate or unstable.