J. E. J. Schmitz

Electrochemical investigations on bis(azaborolinyl)-cobalt and -iron sandwich complexes

Abstract Sandwich complexes of Co and Fe with the azaborolinyl (Ab(R)) ligand and derivatives of it are studied with normal pulse-, differential pulse- and cycllic voltammetry at a Pt electrode in THF and CH 2 Cl 2 solutions, one-electron oxidations being observed. The oxidation process of [Ab(SiMe 3 0] 2 Co is complicated by a substitution of the SiMe 3 group in [Ab(SiMe 3 )] 2 Co + by an alkyl group of the tetraalkyl ammonium ion used as supporting electrolyte. The oxidation of the Fe-complexes in the case that R = SiMe 3 is nearly completely reversible; however with R = H or t-Bu the oxidized products are not stable. The observed trends in redox potentials can be explained with structural and electronic properties of the complexes.

The oxidation of Sn(II) diphosphonates by pertechnetate followed with differential pulse polarography and Mössbauer spectroscopy

Abstract The polarographic reduction and oxidation behaviour of tin(II) sulphate solutions (0.033 M ((CH 3 ) 4 N) 2 SO 4 ) was studied in the presence of various diphosphonates (MDP, EHDP, DCMDP, pCPMDP and DPD) in the pH range 2.5–8.5 at a dropping mercury electrode. Several tin species are present in these solutions and their concentrations vary with pH. Titration of these tin-diphosphonate solutions with pertechnetate in an argon atmosphere, followed by differential pulse polarography, revealed that four electrons are transferred and Tc(III) is formed. A three electron transfer was found for tin- pCPMDP solutions only. Sn-Mossbauer spectroscopic measurements made on EHDP-tin samples oxidized with various quantities of TcO4− confirmed the four etectron transfer.

An electrochemical study on the oxidation of tris(N,N-dimethyldithiocarbamato)ruthenium(III)

Abstract The electrochemical oxidation of Ru(Me 2 dtc) 3 (where Me 2 dtc= N , N -dimethyldithiocarbamate) in acetone or methylene chloride solution is a one- electron process followed by a dimerisation. This is concluded from cyclic voltammetric experiments at different scan rates, concentrations and temperatures with the use of Saveants diagnostic criteria. NMR spectra taken at different temperatures confirm this conclusion. This behaviour is in contrast with that in coordinating solvents like acetonitrile where the one-electron oxidation is followed by addition of a solvent molecule to the coordination sphere, yielding Ru(Me 2 dtc) 3 (CH 3 CN).