Insight into the dynamic ligand exchange process involved in bipyridyl linked arene ruthenium metalla-rectangles

The dynamic ligand exchange behavior of cationic arene ruthenium metalla-rectangles of the type [(p-cymene)4Ru4(OO?OO)2(N?N)2]4+ (OO?OO = oxalato, 2,5-dioxydo-1,4-benzoquinonato, 5,8-dioxydo-1,4-naphthoquinonato; N?N = 4,4'-bipyridine-H8, 4,4'-bipyridine-D8) has been studied in soln. The robustness of the rectangular architecture has been evidenced by NMR and ESI mass spectrometry. Thermodn. and kinetic aspects of the ligand exchange process have been explored using 1H/2D isotope labeling of the 4,4'-bipyridine connectors. This study shows that ligand exchange does not proceed spontaneously for these metalla-assemblies, even at high temp., unless an external stimulus is applied. [on SciFinder(R)]