Synthesis of iron thienyl complexes

Dimetallation of thiophene (TH2), bithiophene (BTH2) and 3,6-dimethyl[3,2-b]thienothiophene (TTH2) using a slight excess of butyl lithium, followed by the addition of [FeCp(CO)2I], resulted in the formation of [2,5-{FeCp(CO)2}2T], 1 and [2-{FeCp(CO)2}T]. The analogous reaction with bithiophene as precursor afforded similar products [2,2′-{FeCp(CO)2}2BT] 2 and [2-{FeCp(CO)2}BTH] 3. In addition to the expected mono- ([2-{FeCp(CO)2}-TTH] 4) and binuclear ([2,2′-{FeCp(CO)2}2-TT] 5) products, dimetallation of 3,6-dimethyl[3,2-b]thienothiophene and the subsequent reaction with [FeCp(CO)2I] yielded carbonyl inserted mono-([2-{FeCp(CO)2}C(O)-{TT}2H] 6) and binuclear ([2-{FeCp(CO)2}C(O)-{TT}2-2′-{FeCp(CO)2}] 7) carbon–carbon coupled products. The precursor [2,7-{SnMe3}2-TT] (8) was prepared and reacted with [FeCp(CO)(PEt3)I] in the presence of a palladium catalyst to afford [2-{FeCp(CO)(PEt3)}C(O)-{TT}2-2′-{SnMe3}] 10.

Graphical abstractMetallated thienothiophene reacts with [FeCp(CO)(L)I] and afforded, after carbonyl insertion and thienothiophene carbon–carbon coupling reactions, the complexes 6, 7 and 10.Figure optionsDownload full-size imageDownload as PowerPoint slide