Ring opening of methylbenzothiophenes and methyldibenzothiophenes by tris(triethylphosphine)platinum(0)

The reaction of[Pt(PEt3)(3)], 1, With 3-methylbenzothiophene and 2-methylbe nzothiophene afforded the thiaplatinacycles [(Et3P)(2)Pt(C,S-C9H8S)], 3 and 4, respectively. In the formation of both complexes (Et3P)(2)Pt has insert ed into the C-S bond to the vinylic carbon. Complex 4 rearranges in solutio n to a dimeric thiaplatinacycle, 5, in which the platinum has moved from ly ing between the vinylic C-S bond into the aromatic C-S bond. Reaction of 1 with 4-methyldibenzothiophene gave a mixture of isomeric thiaplatinacycles [(Et3P)(2)Pt(C,S-C13H10S)], 6 and 7. The reaction of 1 with 4,6-dimethyldib enzothiophene containing some 1,9-dimethyldibenzothiophene led to the isola tion of complex 9, [(Et3P)(2)Pt(C,S-C14H12S)] This is derived from 1,9-dime thyldibenzothiophene, which is a byproduct in the preparation of 4,6-dimeth yldibenzothiophene by a metalation pathway. The reaction of 1 with highly p ure 4,6-dimethyldibenzothiophene gave the hydride complex, 10, in which (Et 3P)(2)Pt has inserted into the C-H bond at the 3-position. The thiaplatinac ycle cis-[(Et3P)(2)Pt(eta(2)-C,S-C14H12S)], 8, was obtained by reaction of highly pure 4,6-dimethyldibenzothiophene with cis-[PtCl2(PEt3)(2)] and meta llic sodium under hydrogen. X-ray structures of complexes 3, 5, and 9 are r eported.