Electrochem. data of 4 bis chelate bridged complexes Ru(bpy)22(μ, η4-L)n+ (bpy = 2,2'-bipyridine, L = sym. N heterocycle such as 3,6-di-2-pyridyl-1,2,4,5-tetrazine, 2,5-di-2-pyridylpyrazine, 2,2'-bipyrimidine or azo-2,2'-bipyridine) show conclusively that the electron d. at the coordination centers in the LUMO of the bridging p ligand dets. the comproportionation const. of the RuIIRuIII mixed-valence state (n = 5). Neither the no. of mediating p centers nor the distance or the orientation of the 2 metal centers plays a significant role. The presence of 2 equiv chiral metal centers in these complexes leads to formation of meso and DL diastereomers, as shown for one example by 1H NMR. on SciFinder(R)
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