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((NN)-N-boolean AND)(MeCN)(2)(2-Ph-2'-Py)]PF6 (2-Ph-2'-Py = ortho-metalated 2-phenylpyridline, (NN)-N-boolean AND = phenanthroline, 2,2'-bipyridine), in which one of the nitrogens of the (NN)-N-boolean AND 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'-R-2-2,2'-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) Ru-II 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.