Synthesis and Linkage Isomerization of Thiolato-Bridged Ru^IIAg^IRu^II Trinuclear Complex with d-Penicillaminate

The reaction of [Ru(solvent)2(bpy)2]2+ (bpy = 2,2′-bipyridine) with d-H2pen (d-penicillamine) in ethanol/water in the presence of Ag+ gave a thiolato-bridged RuIIAgIRuII trinuclear complex, [Ag{Ru(d-Hpen)(bpy)2}2]3+ ([1]3+), in which two octahedral [RuII(d-Hpen)(bpy)2]+ units are linked by a linear AgI ion. Of three possible isomers (ΔDΔD, ΔDΛD, and ΛDΛD), [1]3+ formed the ΔDΔD and ΛDΛD isomers that were separately isolated by fractional crystallization with the use of [Sb2(R,R-tartrato)2]2−. In [1]3+, each d-Hpen ligand chelates to a RuII 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 ΔDΔD isomer of [1]3+ was converted to ΔDΔD-[2]3+, in which each d-Hpen ligand chelates to a RuII 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 ΛDΛD isomer of [1]3+ under the same conditions. The isolated ΔDΔD-[1]3+, ΛDΛD-[1]3+, and ΔDΔD-[2]3+ were fully characterized by electronic absorption, CD, and NMR spectroscopies, along with single-crystal X-ray crystallography for ΛDΛD-[1]3+ and ΔDΔD-[2]3+.