Tris- and pentakis-dialkyldithiocarbamates of ruthenium, [Ru(S2CNR2)3]nand [Ru2(S2CNR2)5]n (n = +1, 0, and –1): chemical and electrochemical interrelations

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Abstract
The electron-transfer characteristics of many ruthenium(III) dithiocarbamates have been studied in acetone at a platinum electrode. The tris complexes undergo a relatively facile, reversible, one-electron reduction step to yield the ruthenium(II) complexes [Ru(S2CNRR′)3]–(R,R′= Me, Et, Pri, Bui, Ph, PhCH2, C6H11; RR′= piperidinyl, 2,6-dimethylpiperidinyl, pyrrolrdinyl, or morpholinyl). The corresponding one-electron oxidation step to the formally ruthenium(IV) complex [Ru(S2CNRR′)3]– is not reversible, the degree of irreversibility being markedly dependent on the substituents R and R′. Substituent effects on the redox potentials parallel those reported previously for many first-row transition-metal dithiacarbamates. Chemical and electrolytic oxidation of [Ru(S2CNR2)3] yield the dimeric ruthenium(III) cations [Ru2(S2CNR2)5]+ which are obtained in two structural isomeric forms, α and β. Both series (α and β) undergo successive one-electron reductions to the corresponding [Ru2(S2CNR2)5] and [Ru2(S2CNR2)5]– complexes. The rates of isomerisations (i) and (ii) have been measured. β-[Ru2(S2CNMe2)5]–→α-[Ru2(S2CNMe2)5]–(i), α-[Ru2(S2CNMe2)5]+→β-[Ru2(S2CNMe2)5]+(ii) The combined redox-potential data and equilibrium measurements afford the relative thermodynamic stabilities of the six dimeric species. Many of the new complexes have been characterised by spectroscopic techniques including i.r., visible–u.v., and 1H n.m.r. Paramagnetic shift reagents have been employed and, in the case of β-[Ru2(S2CNMe2)5]+, enantiomers have been distinguished with an optically active shift reagent.

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