Carbonylrhodium complexes of pyridine ligands and their catalytic activity towards carbonylation of methanol

The cis ‐[Rh(CO) 2 ClL] (1) complexes, where L = 2‐methylpyridine (a), 3‐methylpyridine (b), 4‐methylpyridine (c), 2‐phenylpyridine (d), 3‐phenylpyridine (e), 4‐phenylpyridine (f), undergo oxidative addition reactions with various electrophiles, like CH 3 I, C 2 H 5 I, C 6 H 5 CH 2 Cl or I 2 , to yield complexes of the types [Rh(CO)(COR)ClXL] (2) (where R = CH 3 (i), C 2 H 5 (ii), X = I; R = C 6 H 5 CH 2 (iii), X = Cl) or [Rh(CO)ClI 2 L] (3) and [Rh(CO) 2 ClI 2 L] (4). The pseudo‐first‐order rate constants of CH 3 I addition with complexes 1 containing pyridine (g) and 2‐substituted pyridine (a and d) ligands were found to follow the order pyridine >2‐methylpyridine >2‐phenylpyridine. The catalytic activity of complexes 1 containing different pyridine ligands (a–g) on carbonylation of methanol was studied and, in general, a higher turnover number was obtained compared with that of the well‐known species [Rh(CO) 2 I 2 ] − . Copyright © 2002 John Wiley & Sons, Ltd.