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.