Dicarbonylrhodium(I) complexes of pyridine alcohol ligands and their catalytic carbonylation reaction

Reaction of dimeric complex [Rh(CO)2Cl]2 with two molar equivalent of pyridine alcohol ligands (L) like 2-hydroxymethylpyridine (a), 3-hydroxymethylpyridine (b) and 4-hydroxymethylpyridine (c) afford the rhodium(I) dicarbonyl complexes [Rh(CO)2ClL](1a–c). The ligands are coordinated to the metal center through N-donor site. The complexes 1 undergo oxidative addition (OA) reactions with various alkyl halides (RI) like CH3I, C2H5I to produce Rh(III) complexes of the type [Rh(CO)(COR)IClL], where R = –CH3(2), –C2H5(3). Kinetic data for the reaction of 1 with CH3I indicate a first order reaction. The catalytic activity of the complexes 1 in the carbonylation of methanol was higher than that of the well known species [Rh(CO)2I2]−.

Graphical abstractRhodium(I) complexes of the type, [Rh(CO)2ClL] L = 2-hydroxymethylpyridine, 3-hydroxymethylpyridine and 4-hydroxymethylpyridine have been synthesized. The complexes show higher efficiency as catalyst for carbonylation of methanol to acetic acid and methyl acetate at 130 ± 5 °C and 30 ± 5 bar pressure than the industrially used species [Rh(CO)2I2]−.Figure optionsDownload full-size imageDownload as PowerPoint slide