Preparations of sulfido-tricobalt clusters containing pyridyl type ligands: insertion of carbon monoxide into cobalt-carbon bond

The reaction of 2-mercaptopyridine with 1.5 M equivalent of CO,(CO)S in THF at 25 C for 1 h gave a sulfido-tricobalt cluster (mu(3)-S)Co-3(CO)(7)(mu-C,N-C5H4N) (1). Further reaction of 1 with diphenyl-2-pyridylphosphine (PPh(2)py) under mild reaction condition afforded a PPh(2)py bridged complex (mu(3)-S)Co-3(CO)(5)[(mu-C(=O),N-C5H4N(C=O))(mu-P,N-PPh(2)py)] (3). The X-ray structure analysis of 3 revealed that a carbonylation process occurred at the Co-C(pyridyl) bond of 1. Carbonylation of 1 at the same position also took place under 1 atm of carbon monoxide at room temperature and formed (mu(3)-S)Co-3(CO)(7)[(mu-C(=O),N-C5H4N(C=O))] (4). Similar results were obtained in the reaction of 2-quinolinethiol with 1.5 M equivalent of Co,(CO)s. A sulfido-tricobalt cluster (mu(3)-S)Co-3(CO)(7)(mu-C9N6C)H6N) (5) and tris-quinolinethiolate chelated cobalt complex [Co(mu-S,N-SC9H6N)(3)] (6) were obtained. In contrast to 1, carbonylation did not occur in 5 at 1 atm of carbon monoxide even at 60 degreesC for prolonged reaction hours. However, treatment of 5 with PPh(2)py yielded a PPh(2)py coordinated (mu(3)-S)Co-3(CO)(6)[(mu-C,N-C9H6N)(PPh(2)py)] (7) as the major product, which is accompanied with a small amount of PPh,py bridged (mu(3)-S)Co-3(CO)(5)[(mu-C(=O),N-C9H6N(C=O))(mu-P,N-PPh(2)py)] (8). Carbonylation did occur at the Co-C(quinolinyl) bond of 5, even though less efficient than that of 1. while reacted with a PPh,py ligand. The same reaction pattern was observed for the reaction of 2-mercapto-nicotinic acid methyl ester with 1.5 M equivalent of Co-3(CO)(8); a sulfido-tricobalt cluster (mu(3)-S)Co-3(CO)(7)(mu-C,N-C5H3NC(=O)OCH3) (9) was obtained as the major product. The crystal structures of all eight new complexes have been determined. (C) 2002 Elsevier Science B.V. All rights reserved.