Linear-Type S-Bridged Triruthenium Complexes with Aliphatic Aminothiolate Ligands: Synthesis, Characterization, and Properties

Treatment of [RuCl2(DMSO)4] with 2-aminoethanethiol (Haet) in ethanol gave a dicationic triruthenium complex,
[Ru{Ru(aet)3}2]Cl2 ([1]Cl2). Complex [1]Cl2 was also obtained by treatment of RuCl3·nH2O with excess Haet in
water. When [1]2+ was chromatographed on a cation-exchange column of SP-Sephadex C-25, meso (ΔΛ) and
racemic (ΔΔ/ΛΛ) isomers of the corresponding tricationic complex, [Ru{Ru(aet)3}2]3+ ([2]3+), were eluted with
aqueous NaNO3. The racemic isomer of [2]3+ was optically resolved into ΔΔ and ΛΛ isomers by using [Sb2(R,R-tartrato)2]2- as a resolving agent. The molecular structures of ΔΛ- and ΔΔ/ΛΛ-[2](NO3)3 were determined by
X-ray crystallography. In these complexes, the central Ru atom is coordinated by six thiolato groups from two
terminal fac-(S)-[Ru(aet)3] units in an octahedral geometry, forming a linear-type S-bridged triruthenium structure.
The spectroelectrochemical studies on the electronic absorption and CD spectra, together with the electrochemical
studies, demonstrated that [1]2+ and [2]3+ are interconvertible with each other through a one-electron redox process,
retaining the chirality of the triruthenium structure. Their electronic structures were investigated on the basis of
EPR and magnetic susceptibility measurements, which indicated that [1]2+ and [2]3+ have spin ground states of St
= 0 and St = 1/2, respectively. The corresponding l-cysteinato complex, [Ru{Ru(l-cys-N,S)3}2]3-, which was
formed from RuCl3·nH2O and excess l-cysteine (l-H2cys) in water followed by air oxidation, is also presented.