PREPARATION AND SOME PROPERTIES OF LINEAR-TYPE S-BRIDGED IRIIICOIIIIRIII TRINUCLEAR COMPLEXES WITH 2-AMINOETHANETHIOLATE (AET) OR L-CYSTEINATE (L-CYS) - CRYSTAL-STRUCTURE OF DELTA LAMBDA-[CO(IR(AET)3)2](NO3)3

The reactions of newly prepared fac(S)-[Ir(III)(aet)3] or DELTA(LLL)-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 DELTA(LLL)DELTA(LLL)-[CoIII{IrIII(L-cys-N,S)3}2]3-. The aet trinuclear complex was separated and optically resolved into the DELTALAMBDA, DELTADELTA, and LAMBDALAMBDA isomers and the crystal structure of the DELTALAMBDA isomer was determined by X-ray diffraction. [Co{Ir(aet)3}2](NO3)3.2H2O, chemical formula C12H40N9S6O11CoIr2, crystallizes in the triclinic, space group P1BAR with a=8.945(2), b=12.073(3), c=8.849(3) angstrom, alpha=110.36(2), beta=102.55(2), gamma=70.88(2)degrees, U=841(2) angstrom3, 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 DELTA- and LAMBDA-fac(S)-[Ir(aet)3] terminals. The other trinuclear complexes were characterized by their absorption, CD, and C-13 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 Ir(III)Co(III)Ir(III) complexes are discussed in comparison with those of the corresponding Rh(III)Co(III)Rh(III) and Co(III)Co(III)Co(III) complexes.