Reactions of benzene based half sandwich ruthenium(II) complex with 2,6-bis((phenylseleno)methyl)pyridine: Preferential substitution of ring resulting in a catalyst of high activity for oxidation of alcohols

[2,6-Bis((phenylseleno)methyl)pyridine] (L) a (Se, N, Se) pincer ligand synthesized by reacting PhSe− (in situ generated) with 2,6-bis(chloromethyl)pyridine reacts with [{(η6-C6H6)RuCl(μ-Cl)}2] (2:1 molar ratio) by preferential substitution of ring resulting in the first Ru-(Se, N, Se) pincer ligand complex, mer-[Ru(CH3CN)2Cl(L)][PF6](1).H2O. Similar reaction in 4:1 molar ratio results in mer-[Ru(L)2][ClO4]2(2). The 1H, 13C{1H} and 77Se{1H} NMR spectra of L, 1 and 2 were found characteristic. The single crystal structures of 1 and 2 were studied by X-ray crystallography. The geometry of Ru in both the complexes is distorted octahedral. The Ru–Se distances are in the ranges 2.4412(16)–2.4522(16) and 2.4583(14)–2.4707(15) Ǻ respectively for 1 and 2. The structural solutions from the crystal data in case of 2, due to inferior quality of its crystals, are suitable for supporting bonding mode of L with Ru(II) only. The 1 shows high catalytic activity for oxidation of primary and secondary alcohols (TON up to 9.7 × 104).

Graphical AbstractThe (Se, N, Se) pincer ligand [2,6-bis((phenylseleno)methyl)pyridine](L) and their somewhat distorted octahedral complexes mer-[Ru(CH3CN)2Cl(L)] [PF6](1).H2O and mer-[Ru(L)2] [ClO4]2(2) have been synthesized and characterized by multinuclei NMR, IR and single crystal X-ray diffraction (Ru–Se distance ranges 2.4412(16)-2.4707(15) Ǻ). The catalytic activity of 1 for oxidation of alcohols is high (TON up to 9.7 × 104).Figure optionsDownload as PowerPoint slide