Analysis of electrolysis reactions of metal complexes using on-line electrospray ionization mass spectrometry with a compact electrolytic flow-through cell

An on-line electrospray ionization mass-spectrometric analysis fbr an elect rolysis reaction was developed by the installation of a compact, efficient flow-through cell upstream of an electrospraying needle. The electrode was designed to avoid any reduction of the oxidation products formed during ele ctrolysis. The electrolytic oxidation reaction of a Ru and Os metal complex was carried out to examine the performance of the system. From the electro lysis of [M(bpy)(3)](PF6)(2) (where M = Ru and Os, and bpy = 2,2'-bipyridin e) we detected the one-electron oxidation product, [M(bpy)(3)](3+). The ele ctrolysis of [Ru(bpy)(2)(en)](ClO4)(2) (en = ethylenediamine) formed two co mplex products along with the elimination of two and four hydrogen atoms fr om the en ligand. The structure of the two complex products was determined to be a monoimine and diimine complex, based on an electrolysis experiment using a deuterium-labeled complex, [Ru(bpy)(2)(ed)](ClO4)(2) (ed = ethylene -d(4)-diamine, H2N-CD2-CD2-NH2). The results indicate that electrochemical oxidation occurs at the ethylenediamine ligand and that the monoimine compl ex is a reaction intermediate for the formation of a diimine complex.