Synthesis, reactivities and catalytic carbonylation of rhodium(I) carbonyl complexes containing isomeric acetylpyridine ligands

[Rh(CO)2Cl]2 reacts with two mole equivalent of 2-acetylpyridine (a), 3-acetylpyridine (b) and 4-acetylpyridine (c) to afford chelate [Rh(CO)Cl(η2-N∩O)] (1a) and non-chelate [Rh(CO)2Cl(η1-N∼O)] (1b, 1c) complexes, where, N∩O = a, N∼O = b, c. Oxidative addition (OA) of 1a–1c with CH3I and C2H5I yields penta coordinate rhodium(III) complexes, [Rh(COR)ClI(η2-N∩O)] {R = –CH3 (2a); –C2H5 (3a)} and [Rh(COR)(CO)ClI(η1-N∼O)] {R = –CH3 (2b, 2c); –C2H5 (3b, 3c)}. Kinetic study for the reaction of 1a–1c with CH3I indicates a pseudo-first order reaction. The catalytic activity of 1a–1c for the carbonylation of methanol to acetic acid and its ester was evaluated at different initial CO pressures 5, 10 and 20 bar at ∼25 °C and higher turn over numbers (TON = 1581–1654) were obtained compared to commercial Monsanto’s species [Rh(CO)2I2]− (TON = 1000) under the reaction conditions: temperature = 130 ± 1 °C, pressure = 15–32 bar, rpm = 450, time = 1 h and catalyst: substrate = 1: 1900.