Preparation, Stereochemistry, and Reactivity of Linear-Type S-Bridged MCrIIIM (M = RhIII, IrIII) Trinuclear Complexes with 2-Aminoethanethiolate (aet). Crystal Structures of ΔΛ-[Cr{M(aet)3}2]3+

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Abstract S-Bridged trinuclear complexes, [CrIII{M(aet)3}2]3+, (M = RhIII (1), IrIII (2); aet = NH2CH2CH2S−) were newly prepared by the reaction of fac(S)-[M(aet)3] with chromium(III) nitrate. They were separated and optically resolved into the ΔΔ, ΛΛ, and ΔΛ isomers. Of these isomers for 1 and 2, the crystal structures of the ΔΛ isomers (1a and 2a) were determined by an X-ray diffraction method. Each of 1a and 2a consists of two fac(S)-[M(aet)3] subunits, a central Cr atom, three nitrates, and three water molecules, [Cr{M(aet)3}2](NO3)3·3H2O, in which three metals are aligned so as to be exactly linear. The central Cr atom is situated in an octahedral environment with the CrIIIS6 chromophore, which is formed by the coordination of two terminal fac(S)-[M(aet)3] units. The other isomers for 1 and 2 were characterized by the absorption and CD spectra, the molar conductivity, and the magnetic susceptibility. Each cyclic voltammogram of ΔΛ-[Cr{M(aet)3}2]3+ in water showed a reversible redox couple (M(IV)/M(III)) and an irreversible reduction wave (Cr(III)/Cr(II)). The stabilities of the S-bridged MCrIIIM complexes are also discussed in relation to the Cr–S bond strengths.