The chemistry of carbonyl sulfide: Final report, July 1, 1985-February 28, 1986

Molecular orbital calculations using effective core potential (ECP) have been carried out on a variety of complexes of carbonyl sulfide (OCS) with transition metals (Pd and Pt). An initial scan of the potential energy surface (the geometry for the carbonyl sulfide molecule was held constant at its experimental values) was carried out in order to determine the most probable sites for the attack of the transition matal on the carbonyl sulfide molecule. Two sites were shown to be energetically favorable: the approach of the transition metal towards the oxygen atom along the internuclear axis and the approach of the transition metal above or below the C-S bond region. After optimization of these two structures, the second minima was shown to be energetically more stable than the linear arrangement. In this optimum structure, the carbonyl sulfide molecule is bent. The higher affinity of palladium and platinum towards sulfur is shown in the tendency of these transition metal to form eta/sup 2 -/(OCS) type of bonds, in the order Pt > Pd. Dialkylaluminumchloride (R/sub 2/AlCl)-catalyzed ene reactions of carbonyl sulfide as an enophile with alkenes were performed. R/sub 2/AlCl selectively complexed to the thionyl sulfur of OCS, then reacted with different alkenesmore » and formed corresponding alkenyl thioicacids as ene adducts. Those alkenes were limonene (1), ..beta..-pinene (2), and methylenecyclohexane (3). The reaction with 1 gave E and Z 3-(4 -(1'-hydroxy-1' -methyl-cyclohexyl))but-2-ene thiocacid (4) as a major product, which was formed from hydration of the thioicacid, a rearranged conjugated form of the original ene adduct. The reaction with 2 and 3 gave corresponding ..beta..,..gamma..-unsaturated original thioicacids, 2-(2'-(6',6'-dimethylbicyclo(3.1.1)hept-2'-ene))ethane thioicacid (5) and 2-(1' -cyclohexenyl)ethane thioicacid (6), respectively, as major products. 23 refs, 6 tabs.« less