LINKAGE ISOMERIZATION AND ELECTROCHEMICAL-BEHAVIOR OF 2 GEOMETRICAL-ISOMERS OF IMETHYLSULFOXIDE)BIS(T-BUTYLPYRIDINE)RUTHENIUM(II)

The reaction of cis-[RuCl2(dmso)(4)] (dmso = dimethylsulfoxide) with 4 -rert-butylpyridine (tbpy) in chloroform leads to the all cis (ccc) an d the cis,cis,trans (cct) geometrical isomers of [RuCl2(S-dmso)(2)(tbp y)(2)]. The cct isomer exhibits a reversible cyclic voltammogram, ascr ibed to the R(III/II) redox couple with E(1/2) = 1.12 V versus SHE. Th e ccc isomer can be oxidized at E(1/2) = 1.27 V; however, the oxidized species undergoes a relaxation equilibrium, (K-s-->o = 1.59), involvi ng the S-to-O linkage isomerization of a coordinated dmso ligand (k(o- ->s) 1.9 s(-1) and k(o-->s) = 1.2 s(-1)). The isomerization reaction i n the Ru-III ccc isomer is discussed in terms of the competitive effec ts between the S-bound dmso and the tbpy ligands.