Dicarbonylrhodium(I) complexes of benzoylpyridine ligands: Synthesis, reactivity and catalytic carbonylation reaction

Abstract

The new complexes of the type [Rh(CO) 2ClL] ( 1a– c), where L = 2-Benzoylpyridine ( a), 3-Benzoylpyridine ( b) and 4-Benzoylpyridine ( c) have been synthesized and characterized. Oxidative addition ( OA) of 1a– c with CH 3I, C 2H 5I and C 6H 5CH 2Cl afford penta coordinated Rh(III) complexes, [Rh(CO)(COR n )ClXL]{R 1 = -CH 3 ( 2a– c), R 2 = –C 2H 5 ( 3a– c); X = I and R 3 = –CH 2C 6H 5 ( 4a– c); X = Cl}. Kinetic data for the reaction of 1a– c with CH 3I indicate a pseudo-first order reaction. The 1a– c exhibit high catalytic activity in the carbonylation of methanol to acetic acid and its ester and show a higher turn over number ( TON = 1529–1748) than the well known commercial species [Rh(CO) 2I 2] − ( TON = 1000) under the reaction conditions: temperature 130 ± 2 °C, pressure 30 ± 2 bar and time 1 h.