Selective Preparation of a Heteroleptic Cyclometallated Ruthenium Complex Capable of Undergoing Photosubstitution of a Bidentate Ligand

Cyclometallated ruthenium complexes typically exhibit red‐shifted absorption bands and lower photolability compared to their polypyridyl analogues. They also have lower symmetry, which sometimes makes their synthesis challenging. In this work, the coordination of four N,S bidentate ligands, 3‐(methylthio)propylamine (mtpa), 2‐(methylthio)ethylamine (mtea), 2‐(methylthio)ethyl‐2‐pyridine (mtep), and 2‐(methylthio)methylpyridine (mtmp), to the cyclometallated precursor [Ru(bpy)(phpy)(CH(3)CN)(2)](+) (bpy=2,2′‐bipyridine, Hphpy=2‐phenylpyridine) has been investigated, furnishing the corresponding heteroleptic complexes [Ru(bpy)(phpy)(N,S)]PF(6) ([2]PF(6)–[5]PF(6), respectively). The stereoselectivity of the synthesis strongly depended on the size of the ring formed by the Ru‐coordinated N,S ligand, with [2]PF(6) and [4]PF(6) being formed stereoselectively, but [3]PF(6) and [5]PF(6) being obtained as mixtures of inseparable isomers. The exact stereochemistry of the air‐stable complex [4]PF(6) was established by a combination of DFT, 2D NMR, and single‐crystal X‐ray crystallographic studies. Finally, [4]PF(6) was found to be photosubstitutionally active under irradiation with green light in acetonitrile, which makes it the first cyclometallated ruthenium complex capable of undergoing selective photosubstitution of a bidentate ligand.