Preparation and Some Properties of Linear-Type S-Bridged IrIIICoIIIIrIII Trinuclear Complexes with 2-Aminoethanethiolate (aet) or l-Cysteinate (l-cys). Crystal Structure of ΔΛ-[Co{Ir(aet)3}2](NO3)3

Abstract

Abstract The reactions of newly prepared fac(S)-[IrIII(aet)3] or ΔLLL-fac(S)-[IrIII(l-cys-N,S)3]3− with Co2+, followed by the air or H2O2 oxidation, gave linear-type S-bridged trinuclear complexes, [CoIII{IrIII(aet)3}2]3+ and ΔLLLΔLLL-[CoIII{IrIII(l-cys-N,S)3}2]3−. The aet trinuclear complex was separated and optically resolved into the ΔΛ, ΔΔ, and ΛΛ isomers and the crystal structure of the ΔΛ isomer was determined by X-ray diffraction. [Co{Ir(aet)3}2](NO3)3·2H2O, chemical formula C12H40N9S6O11CoIr2, crystallizes in the triclinic, space group with a = 8.945(2), b = 12.073(3), c = 8.849(3) Å, α = 110.36(2), β = 102.55(2), γ = 70.88(2)°, U = 841(2) Å3, Z = 1, and R = 0.059. The central Co(III) has a trigonally distorted octahedral geometry, coordinated by six thiolato sulfur atoms from the octahedral Δ- and Λ-fac(S)-[Ir(aet)3] terminals. The other trinuclear complexes were characterized by their absorption, CD, and 13C NMR spectra. The meso–racemic isomerization, which results from the cleavage of the Co–S bonds, was recognized for [Co{Ir(aet)3}2]3+ in D2O, methanol–H2O, and ethanol–H2O. The cyclic voltammogram of rac-[Co{Ir(aet)3}2]3+ in water showed two almost reversible redox couples at −0.23 V and +0.73 V (vs. Ag/AgCl). The chemical properties of the present IrIIICoIIIIrIII complexes are discussed in comparison with those of the corresponding RhIIICoIIIRhIII and CoIIICoIIICoIII complexes.