Synthetic, electrochemical and structural studies on diruthenium(II/III) and dirhodium(II/II) compounds

This thesis describes the synthetic, structural, and electrochemical studies on compounds containing dirhodium(II/II) and diruthenium(II/III) units. Chapter two describes the preparation of a range of diruthenium(II/III) compounds with the general formula [Ru2(RNOCR')4Cl]. Their electrochemical behaviour has been studied in DMSO. The reduction and oxidation potentials of these compounds have been found to be dependent on the identity and the position of the substituent groups attached to the bridging ligands. The effect of adding silver or chloride ions, to the electrochemical cell, on the number and potential of the redox reactions observed has been investigated. The compound [Ru2(CH3C5H4NNH)3(CH3CO2)Cl], has been studied in detail both structurally and electrochemically and this work is reported in Chapter three. The [Ru2]5+ core of this unusual mixed ligand compound has been reversibly reduced to [Ru2]3+ in two one-electron steps and reversibly oxidised to [Ru2]6+. The effect of chloride and silver ions on the electrochemical behaviour of this compound has also been studied. Turning to rhodium, Chapter four describes attempts to prepare new compounds with the general formula [Rh2(HNOCR)4L2]. These have been unsuccessful, but compounds have been obtained with the general formula [Rh2(O2CR)n(HNOCR')4-nL2] (n=0,1,2,3) which have proved interesting in their own right. These compounds have been studied electrochemically in acetonitrile. The effect of altering the substituent groups R and R' has been studied along with varying n for each set of compounds. Finally, Chapter five investigates a number of dirhodium(II/II) compounds containing mixed bridging and chelating ligands, [Rh2(O2CR)2(R'COCHCOR'')2(C5H5N)2] (R=CH3,C2H5,C(CH3)3; R',R''=CH3,CF3). These compounds have been fully characterised using infrared, 1H n.m.r., and 19F n.m.r. spectroscopy, mass spectrometry and microanalysis. Crystal structures of four of these compounds have been reported. The compound, [Rh2(O2CCH3)2(CH3COCHCOCF3)2(C5H5N)2], has been separated into cis and trans isomers using column chromatography. The structures of each of these isomers reveal a coupling between adjacent molecules in the unit cell via Rh-C interactions