Cleavage of Ru-C(aryl) bond of a four-membered ortho-metalated ruthenium(II) organometallics by mercaptopyrimidine and pyridine-2,6-dicarboxylate ligands: spectroscopic, structural and computational studies

The heterogeneous phase reaction of Ru(η2-RL)(PPh3)2(CO)Cl (1) with 2-mercaptopyrimidine(pymSH) and pyridine-2,6-dicarboxylate(dipic) ligands afforded the complexes of the type Ru(PPh3)(CO)(pymS)2 (2) and Ru(PPh3)2(CO)(dipic) (3) in excellent yield respectively. The chelation of pymS/dipic is attended with the cleavage of Ru-O, Ru-Cl and Ru-C(aryl) bonds and the RL ligand is no longer coordinated with the metal center in the products. The spectral (UV-Vis, IR, 1H NMR) and electrochemical data of the complexes are included. In dichloromethane solution both 2 and 3 display one quasi-reversible RuIII/RuII cyclic voltammetric response with E1/2 in the range 1.15-1.50 V vs Ag/AgCl. Structure determinations of 2 and the solvate 3·CH3CN have revealed distorted octahedral RuCN2S2P coordination sphere for 2 and RuCNO2P2 coordination sphere for 3·CH3CN. For 2 the pairs (P, N), (S, S) and (C, N) define the three trans directions whereas for 3·CH3CN those pairs are (P, P), (C, N) and (O, O). The electronic structures and the absorption spectra of 2 and 3 are also scrutinized by the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) analysis.