Synthesis and linkage isomerization of thiolato-bridged Ru(II)Ag(I)Ru(II) trinuclear complex with D-penicillaminate.

The reaction of [Ru(solvent)(2)(bpy)(2)](2+) (bpy = 2,2'-bipyridine) with D-H(2)pen (D-penicillamine) in ethanol/water in the presence of Ag(+) gave a thiolato-bridged Ru(II)Ag(I)Ru(II) trinuclear complex, [Ag{Ru(D-Hpen)(bpy)(2)}(2)](3+) ([1](3+)), in which two octahedral [Ru(II)(D-Hpen)(bpy)(2)](+) units are linked by a linear Ag(I) ion. Of three possible isomers (Delta(D)Delta(D), Delta(D)Lambda(D), and Lambda(D)Lambda(D)), [1](3+) formed the Delta(D)Delta(D) and Lambda(D)Lambda(D) isomers that were separately isolated by fractional crystallization with the use of [Sb(2)(R,R-tartrato)(2)](2-). In [1](3+), each D-Hpen ligand chelates to a Ru(II) center through thiolate and carboxylate groups, while an amine group of D-Hpen is protonated and does not participate in the coordination. On refluxing in ethanol/water, the Delta(D)Delta(D) isomer of [1](3+) was converted to Delta(D)Delta(D)-[2](3+), in which each D-Hpen ligand chelates to a Ru(II) center through thiolate and amine groups with a non-coordinating carboxyl group. On the other hand, a similar thermal linkage isomerization was not noticed for the Lambda(D)Lambda(D) isomer of [1](3+) under the same conditions. The isolated Delta(D)Delta(D)-[1](3+), Lambda(D)Lambda(D)-[1](3+), and Delta(D)Delta(D)-[2](3+) were fully characterized by electronic absorption, CD, and NMR spectroscopies, along with single-crystal X-ray crystallography for Lambda(D)Lambda(D)-[1](3+) and Delta(D)Delta(D)-[2](3+).