Insertion of rhodium into the carbon-sulfur bond of thiophene. Mechanism of a model for the hydrodesulfurization reaction

Article abstract of DOI:10.1021/ja00002a025

The reaction of (C₅Me₅)Rh(PMe₃)(Ph)H with thiophene leads to the elimination of benzene and oxidative addition of the thiophene C-S bond across the Rh(I) center, giving (C₅Me₅)Rh(PMe₃)(SCH=CHCH=CH). Similar reactions occur with 2-methylthiophene, 3-methylthiophene, 2,5-dimethylthiophene, benzothiophene, and dibenzothiophene. Selectivity studies performed with these complexes are consistent with the coordination of sulfur to rhodium prior to C-S bond cleavage. Reversible reductive elimination of thiophene occurs at ～80°C. The diene portion of the C-S insertion ligand undergoes a Diels-Alder reaction with dimethyl acetylenedicarboxylate to give dimethyl phthalate as a major product. The dimethylthiophene complex (C₅Me₅)Rh(PMe₃)(SCMe=CHCH=CMe) was structurally characterized, crystallizing in the monoclinic space group P1 with a = 8.707 (8) A?, b = 14.157 (15) A?, c = 8.637 (5) A?, α = 100.90 (8)°, β = 106.07 (6)°, γ = 87.85 (8)°, V = 1004 (3) A?³, and Z = 2.