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


The heterogeneous phase reaction of excess sodium salt of 2-hydroxypyridine (OHpy) with [Ru(kappa C-2,O-RL)(PPh3)(2)(CO)Cl] (1) afforded complexes of the type [Ru(kappa C-1-RL)(PPh3)(2)(CO)(Opy)] (2) in excellent yield [kappa C-2,O-RL is 4-methyl-6-((N-R-arylimino)methyl)phenolato-C-2,O), kappa C-1-RL is 4-methyl-6-((N-R-arylimino)methyl)phenol-C-2) 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 Ru-III/Ru-II cyclic voltammetric response with E-1/2 in the range 0.65-0.69 V versus Ag/AgCl. The crystal and molecular structures of [Ru(kappa C-1-HL)(PPh3)(2)(CO)(Opy)]center dot 2C(6)H(6)center dot 0.5H(2)O, 2(H)center dot 2C(6)H(6)center dot 0.5H(2)O and [Ru(kappa C-1-ClL)(PPh3)(2)(CO)(Opy)]center dot 2C(6)H(6)center dot 0.25H(2)O, 2(Cl)center dot 2C(6)H(6)center dot 0.25H(2)O 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. [GRAPHICS] .



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Islam, A; Ghosh, MK; Mondal, S; Brandao, P; Chattopadhyay, S

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M. K. Ghosh and S. Mondal thank University Grants Commission (UGC), India, for the predoctoral fellowships. The crystallographic studies were supported by CICECO-Aveiro Institute of Materials (UID/CTM/50011/2013), financed by National Funds through the FCT/MEC and co-financed by QREN-FEDER through COMPETE under the PT2020 Partnership Agreement. Financial supports from the Department of Science and Technology, Government of India (no. SR/S1/IC-65/2010) and the Council of Scientific & Industrial Research, New Delhi, India (no. 01(2898)/17/EMR-II) are gratefully acknowledged, University of Kalyani for infrastructural facilities. The support of DST under FIST program to the Department of Chemistry, University of Kalyani is also acknowledged.

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