Synthesis, characterization, and stereochemistry of S-bridged Co(III)MCo(III)(M = Pd(II), Pt(II)) trinuclear complexes containing two non-bridging thiolato groups: building blocks for the construction of chiral heterometallic aggregates

The reaction of fac(S)-Co(aet)(3)](aet = aminoethanethiolate) with PdCl(4)](2-) in a 2:1 ratio in water gave an S-bridged Co(III)Pd(II)Co(III) trinuclear complex composed of two mer(S)-Co(aet)(3)] units, PdCo(aet)(3)](2)](2+)(1](2+)). In 1](2+), each of the two mer(S)-Co(aet)(3)] units is bound to a square-planar Pd(II) ion through two of three thiolato groups, leaving two non-bridging thiolato groups at the terminal. Of two geometrical forms, syn and anti, possible for PdCo(aet)(3)](2)](2+), which arise from the difference in arrangement of two terminal non-bridging thiolato groups, 1](2+) afforded only the syn form. A similar reaction of fac(S)-Co(aet)(3)] with PtCl(4)](2-) or trans-PtCl(2)(NH(3))(2)] produced an analogous Co(III)Pt(II)Co(III) trinuclear complex, PtCo(aet)(3)](2)](2+)(2](2+)), but both the syn and anti forms were formed for 2](2+). Complexes 1](2+) and syn- and anti-2](2+), which exclusively exist as a racemic(DeltaDelta/LambdaLambda) form, were successfully optically resolved with use of Sb(2)(R,R-tartrato)(2)](2-) as the resolving agent. The reaction of syn-2](2+) with AuClS(CH(2)CH(2)OH)(2)]] led to the formation of an S-bridged Co(III)(4)Pt(II)(2)Au(I)(2) octanuclear metallacycle, Au(2)PtCo(aet)(3)](2)](2)](6+)(3](6+)), while the corresponding reaction of anti-2](2+) afforded a different product (4](3+)](n)) that is assumed to have a polymeric structure in AuPtCo(aet)(3)](2)]](3+)](n).