Rational Synthesis of Heteroleptic Tris(chelate) Ruthenium Complexes [RuII(2-Ph-2′-Py)(L∧L)(L′∧L′)]PF6 by Selective Substitution of the Ligand Trans to the Ruthenated Phenyl Ring

[Ru(N∧N)(MeCN)2(2-Ph-2′-Py)]PF6 (2-Ph-2′-Py = ortho-metalated 2-phenylpyridine, N∧N = phenanthroline, 2,2′-bipyridine), in which one of the nitrogens of the N∧N ligand is bound to Ru trans to the phenyl unit of 2-PhPy, were slowly isomerized (2 days) in refluxing 1,1-dichloroethane/MeCN (9/1) or more rapidly (although with a reduced yield) in the presence of UV light, to afford compounds in which the same N atom was bound to Ru trans to the pyridine of 2-PhPy; these new compounds, in opposition to their well-known isomers, proved to be nicely reactive toward substitution reactions of the MeCN ligands, by other bidentate N-containing ligands such as 4,4′-R2-2,2′-bipyridine (R = H, OMe, COOH) and 4,7-dimethyl-1,10-phenanthroline. These results question the exact structure of the already reported heteroleptic tris(chelate) RuII complexes obtained from the same starting material in which the incoming bidentate ligands were incorrectly believed to be bound to the Ru atom at positions trans to N atoms.