Preparation, characterization, and some properties of novel dinuclear complexes with a coordinated bridging disulfide bond.: Crystal structures of ΔRΛS-[M2(2-aminoethanethiolato)4(cystamine)]2+ (M = IrIII, RhIII)

Novel dinuclear complexes, [M-2(aet)(4)(cysta)](2+) (M = Ir-III (1), Rh-III (2); aet = NH2CH2CH2S-, cysta = NH2CH2CH2SSCH2CH2NH2), were prepared by the oxidation reactions of fac(S)-[M(aet)(3)]. The crystal structures of the complexes were determined by X-ray diffractions: 1Cl(2). 4H(2)O, monoclinic, P2(1)/a, a = 12.427(2), b = 8.879(1), c = 13.387(1)Angstrom, beta = 91.947(10)degrees, V = 1476.3(3) Angstrom(3), Z = 2, and R = 0.031; 2Cl(2). 2H(2)O, monoclinic, P2(1)/c, a = 11.788(2), b = 8.485(1), c = 14.800(2) Angstrom, beta = 112.980(9)degrees, V = 1362.9(3) Angstrom(3), Z = 2, and R = 0.023. In the structures of 1 and 2, two octahedral fac(S)-[M(aet)(3)] units are linked by a coordinated disulfide bond. Their disulfide sulfur atoms are bound to the Ir and Rh atoms more strongly than to the Co atom. Both complexes 1 and 2 take only the Delta(R)Lambda(S) configuration of ten possible isomers. The electronic absorption, (CNMR)-C-13, and infrared spectra exhibit characteristic behavior in relation to the disulfide bond. 1 and 2 are fairly stable in water, and their structures in solid are retained in solution. The reduction or oxidation of the dinuclear complexes causes a cleavage of the disulfide bond to afford the mononuclear thiolato or sulfinato complexes. The properties of the present complexes are also discussed in comparison with those of the mononuclear and/or polynuclear complexes with the corresponding metal ions.