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Chemistry of a New Family of Carboxyl-Chelated Ruthenium and Osmium Aryls Incorporating the Imine−Phenol Motif

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journal contribution
posted on 01.10.1996, 00:00 authored by Prasanta Ghosh, Amitava Pramanik, Animesh Chakravorty
The reaction of carbonylhalo[4-methyl-6-(NR-iminiomethyl)phenolato-C2,O]bis(triphenylphosphine)metal(II), MII2-RL)(PPh3)2(CO)X (M = Ru, Os; X = Cl, Br; R = Ph, p-MeC6H4), 1, with sodium carboxylates has afforded carbonyl(carboxylato)[4-methyl-6-(NR-iminomethyl)phenol-C2]bis(triphenylphosphine)metal(II), MII1-RL)(PPh3)2(CO)(η2-R‘CO2) (R‘ = Me, Ph), 2. The reaction is believed to proceed via initial associative cis attack on halide by carboxylate. The reaction 21 occurs upon treatment of 2 with excess halide. Spectral (UV−vis, IR, 1H NMR) and electrochemical (metal redox) data for 2 are reported. Structure determination of Ru(η1-MeC6H4L)(PPh3)2(CO)(η2-MeCO2) and Ru(η1-MeC6H4L)(PPh3)2(CO)(η2-PhCO2)·C6H6 has revealed trans (PPh3)2 geometry, the MeC6H4L ligand being bonded via an aromatic carbon atom lying cis to the CO molecule. In the H-bonded phenol−imine function the bond parameters for the acetate complex are as follows:  O1−H, 1.14(3) Å; N···H, 1.52(3) Å; O1···N, 2.592(10) Å; O1−H···N, 156(1)°. In the 12 interconversion, iminium−phenolate to imine−phenol tautomerization and a sterically controlled change in rotational conformation are involved.