RUTHENIUM AMMINE DISULFIDES

The complex of 1, 2-dithiane with pentaammineruthenium(II) can be prepared by direct substitution on the pentaammineaquo ion, but with the analogous five-membered ligand, preparation by this route is not successful. The disulfide complexes can, however, be prepared by starting with Ru(NH3)5OH2 2+and 1, 4-butanedithiol or 1, 3-propanethiol. The products of these substitution reactions undergo one-electron oxidations to the Ru(III)-thiol state and, on further one-electron oxidation, produce the cyclic disulfides coordinated to Ru(II). This can be further oxidized, in a process which in the case of the six-membered ring was shown to be reversible on the cyclic voltammetric time scale (Ef= 630 mV vs. NHE at 25 °C), to the Ru(III) complex. In contrast to a simple thioether complex of Ru(III) which shows ligand to metal charge transfer at ca. 450 nm, the ruthenium(III) disulfide (six-membered ring) has a band at 618 nm with a second band discernible as a shoulder at 360 nm. The splitting is analogous to that observed with 1, 5-dithiocane as ligand, which has been ascribed to sulfur lone-pair interactions. As expected on this basis, the splitting observed in the Ru(III) complex of the five-membered disulfide is even greater, owing to the fact that the dihedral angle between the sulfur lone pairs is smaller in the five-membered than in the six-membered ring. © 1979, American Chemical Society. All rights reserved.