Search

Preparations of [Rh(Hdmg) 2 (H 2 O) 2 ]ClO 4 ( 1 ) (Hdmg=dimethylgyoximate) from [Rh(H 2 O) 6 ](ClO 4 ) 3 and dimethylglyoxime and of [Rh(Hdmg) 2 (PPh 3 ) 2 ]ClO 4 ( 2 ) from 1 and PPh 3 are described. 1 crystallizes in the space group with a =14.910(3), b =6.058(1), c =18.617(4), A, β =107.649(8)°, Z =4. The structure was refined up to R =0.021 for 1849 reflections. The IR and NMR spectra and electrochemical behavior of 1 and 2 are discussed and compared with other rhodoximes. Three polarographic and CV processed can be detected for 2 , the first two, respectively to Rh(II) and Rh(I), being followed by fast reactions.

Heterogeneous electron transfer rate constants were determined as a function of electrode potential for one-electron oxidation in acetonitrile (AN) at O °C of a series of organocobaloximes [R-Co(DH)2L] bearing widely different organic groups. Reaction entropies were determined by voltammetric half-wave potential (Er 1 2 ) measurements in a non-isothermal cell. The electron transfer coefficients and reorganization parameters were calculated following the Marcus theory. The reaction free energies relative to a reference couple ΔG∘ are linearly correlated with the polar Taft constant of the organic substituent R. The steric effects on ΔG∘ are shown by the correlation of Er sol1 2 with the CoC bond distance. Assuming constancy of double layer effects along the series in the given solution composition, the trends of the apparent rate constants kapp were considered in order to evaluate the effects of the nature of the organic ligand on the activation energy ΔG‡ of the electron transfer. The steric effects on ΔG‡ are pointed out i.a. by consideration of the relationship between ΔG‡ and ΔG∘.