Pyridine-2-olato chelated ruthenium(II) organometallics incorporating imine-phenol function: spectroscopic, structural, electrochemical, and theoretical studies

Abstract

The heterogeneous phase reaction of excess sodium salt of 2-hydroxypyridine (OHpy) with [Ru(κ2C,O-RL)(PPh3)2(CO)Cl] (1) afforded complexes of the type [Ru(κ1C-RL)(PPh3)2(CO)(Opy)] (2) in excellent yield [κ2C,O-RL is 4-methyl-6-((N-R-arylimino)methyl)phenolato-C2,O), κ1C-RL is 4-methyl-6-((N-R-arylimino)methyl)phenol-C2) and R is H, Me, OMe, Cl]. The chelation of Opy is attended with the cleavage of Ru-O and Ru-Cl bonds and iminium-phenolato → imine-phenol prototropic shift. The 1→2 conversion is irreversible and the type 2 species are thermodynamically more stable than the acetate, nitrite, and nitrate complexes of 1. The spectral (UV-vis, IR, NMR) and electrochemical data of the complexes are reported. In dichloromethane solution the complexes display one quasi-reversible RuIII/RuII cyclic voltammetric response with E1/2 in the range 0.65–0.69 V versus Ag/AgCl. The crystal and molecular structures of [Ru(κ1C-HL)(PPh3)2(CO)(Opy)]·2C6H6·0.5H2O, 2(H)·2C6H6·0.5H2O and [Ru(κ1C-ClL)(PPh3)2(CO)(Opy)]·2C6H6·0.25H2O, 2(Cl)·2C6H6·0.25H2O are reported, which revealed a distorted octahedral RuC2P2NO coordination sphere. The pairs (P,P), (C,O), and (C,N) define the three trans directions. The electronic structures of the complexes are also scrutinized by density functional theory.