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

The reaction of carbonylhalo[4-methyl-6-(NR-iminiomethyl)phenolato-C²,O]bis(triphenylphosphine)metal(II), M^II(η²-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), M^II(η¹-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 2 → 1 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 1 → 2 interconversion, iminium−phenolate to imine−phenol tautomerization and a sterically controlled change in rotational conformation are involved.