A comparison of the reactions of PPh 2CH 2SR (R = Me, Ph) with alkyne-bridged dicobalt carbonyl complexes and with an iron dicobalt μ 3-thioxo carbonyl complex

Abstract

The reactions of Ph 2PCH 2SR (R = Me, Ph) in toluene with the dicobalt complexes [Co 2 (μ-R 1CCR 2(CO) 6] (R 1 = R 2 = CO 2Me and R 1 = H, R 2 = CO 2Me) give the monosubstituted complexes [Co 2(μ-R 1CCR 2)(CO) 5PPh 2CH 2SMe] 1 and [Co 2(μ- R 1CCR 2(CO) 5PPh 2CH 2SPh] 2. On heating 1 and 2 in toluene solution, loss of CO leads to the bridged species [Co 2(μ-R 1CCR 2)(μ- PPh 2CH 2SMe)(CO) 4] 3 and [Co 2 (μ -R 1CCR 2)(μ-PPh 2CH 2SPh)(CO) 4] 4. This transformation is readily reversed by treatment of 3 and 4 with CO, showing the Co-S bond in these complexes to be relatively weak. Similar reactions of Ph 2PCH 2SR (R = Me, Ph) with [Co 2Fe(μ 3-S)(CO) 9], however, give only the ligand bridged species [Co 2Fe(μ 3-S)(μ-Ph 2PCH 2SR)(CO) 7] (R = Me 5 and R = Ph 6). Treatment of 5 and 6 with CO causes cleavage of the Co-S bond but, in contrast to 3 and 4, the ligand bridged species readily reform when the CO purge ceases. The structures of 3a and 6 have been confirmed by single-crystal X-ray analysis.