Synthesis, characterization, and structure of cyclopenta[c]thiophenes and their manganese complexes

1,3-Diaryl-4H-cyclopentac]thiophenes are efficiently prepared from 1,2-diaroylcyclopentadienes by use of Lawesson's reagent. eta5-Cyclopentac]thienyl complexes, Mn(eta5-SC7H3-1,3-R2)(CO)3] (R = Me, Ph), are prepared in high yield by ligand substitution reactions of MnBr(CO)5] with SnMe3(SC7H3-1,3-R2)]. Alternatively, thiation with P4S10/NaHCO3 converts Mn{eta5-1,2-C5H3(COR)2)(CO)3] to Mn(eta5-SC7H3-1,3-R2)(CO)3] (R = Ph, 4-tolyl, 4-MeOC6H4, benzo2,3-b]thienyl). The molecular structures of complexes with R = Me, Ph show planar eta5-cyclopentac]thienyl ligands, with the manganese atom slightly displaced away from the ring-fusion bond.