Newly synthesized rhodium(I) carbonyl complexes of the type [Rh(CO)(2)C1L] (1), where L = alpha,N-diphenylnitrone (a), alpha-styryl-N-phenyinitrone (b), N,N'-diphenyldinitrone (c) and alpha-(2-furyl)-N-phenylnitrone (d), act as efficient catalyst precursors (maximum turn over number (TON) 1200-1400 per 90 min) for carbonylation of methanol to produce acetic acid and its ester at temperature 150 +/- 10 degreesC and pressure 20 bar. (C) 2002 Elsevier Science B.V. All rights reserved.