SYNTHESIS AND PROPERTIES OF T-CAGE-TYPE S-BRIDGED (RHZNII)-ZN-III OCTANUCLEAR COMPLEXES WITH 2-AMINOETHANETHIOLATE OF L-CYSTEINATE

The reactions of fac(S)-[Rh(aet)(3) or Delta(LLL)-fac(S)-[Rh(L-cys-N,S)3](3-) with a mixture of Zn2+ and ZnO in water produced T-cage-type S-bridged octanuclear complexes with a [(Zn4O)-O-II](6+) core, [{Rh(aet)(3)}4Zn4O](6+) (1) and Delta(LLL)Delta(LLL)Delta(LLL)Delta(LLL)-[{Rh(L-CYS-N,S)(3)}4Zn4O](6-) (2). A similar T-cage-type complex with a [(Zn3.7Co0.3O)-Co-II-O-II](6+) core, [{Rh(aet)(3)}4Zn3.7Co0.3O](6+) (3), was derived from a linear-type S-bridged trinuclear complex, [Co-III{Rh(aet)(3)}(2)](3+), by reacting with Zn powder in water, followed by adding Zn2+. The chloride, bromide, and nitrate salts of 1 and 3 were commonly subject to spontaneous resolution to give only two isomers, (+)(350)(CD)-Delta Delta Delta Delta and (-)(350)(CD)-Delta Delta Delta Delta. The crystal structure and absolute configuration of the (-)(350)(CD) isomer for each of 1Br(6) and 3Br(6) were determined by X-ray crystallography. (-)(350)(CD)-1Br(6).9H(2)O crystallizes in the cubic space group P2(1)3 with a = 19.017(1) Angstrom A, V= 6876.9(4) Angstrom A(3), Z=4, R=0.0519, and R(w)=0.0475. (-)(350)(CD)-3Br(6).8H(2)O also crystallizes in the cubic space group P2(1)3 with a=18.922(1)Angstrom A, V=6775.3(4)Angstrom A(3), Z=4, R=0.0495, and R(w)=0.0430. In 1 the four octahedral fac(S)-[Rh(aet)(3)] subunits are bound to the tetrahedral [Zn4O](6+) core in a tetrahedral arrangement, and each Zn(II) is tetrahedrally coordinated by three thiolato sulfur atoms from three different fac(S)-[Rh(aet)(3)] subunits and a central mu(4)-oxygen atom. The chiral configurations are regulated to Delta for all four fac(S)- [Rh(aet)(3)] subunits and R for all 12 asymmetric bridging sulfur atoms in the (-)(350)(CD) isomer of 1, giving a T symmetrical structure. While (-)(350)(CD)-3 was isostructural with (-)(350)(CD)-1, the plasma emission analysis and electronic absorption spectrum indicated that a slight amount of Co(II) is trapped in place of Zn(II) in 3 (Zn:Co = 3.7:0.3). The absorption and circular dichroism (CD) spectral behavior of the present T-cage-type (RhZnII)-Zn-III octanuclear complexes are discussed in comparison with those of the mononuclear fac(S)-[Rh(aet)(3)] and Delta(LLL)-fac(S)-[Rh(L-cys-N,S)(3)](3-) complexes.