Synthesis, Characterization, and Structure of Cyclopenta[<i>c</i>]thiophenes and Their Manganese Complexes

1,3-Diaryl-4H-cyclopenta[c]thiophenes are efficiently prepared from 1,2-diaroylcyclopentadienes by use of Lawesson's reagent. η5-Cyclopenta[c]thienyl complexes, [Mn(η5-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{η5-1,2-C5H3(COR)2)(CO)3] to [Mn(η5-SC7H3-1,3-R2)(CO)3] (R = Ph, 4-tolyl, 4-MeOC6H4, benzo[2,3-b]thienyl). The molecular structures of complexes with R = Me, Ph show planar η5-cyclopenta[c]thienyl ligands, with the manganese atom slightly displaced away from the ring-fusion bond.