Skeletal Modification of Benzothiophene Mediated by Iron Carbonyls: Insertion of Terminal Alkynes with Migration of Amino and Alkoxy Groups

A thiolate-bridged
diiron carbonyl complex derived from benzothiophene, [Fe2(μ-SC6H4CHCH)­(CO)6], reacted
with terminal alkynes HCCR (R = SiMe3, Ph, isobutyl) under
photoirradiation conditions to afford diiron complexes with a 2,4-pentadienoyl
moiety, [Fe2{μ-SC6H4(CH)3C­(R)­CO}­(CO)5], via alkyne and CO insertion. In
a similar reaction with N,N-dimethylpropargylamine,
a diiron complex with a pentadienyl moiety, [Fe2{μ-SC6H4(CH)3C­(NMe2)­CH2}­(CO)5], was obtained as an alkyne insertion product without
CO insertion. This reaction involves 1,2-migration of a dimethylamino
group. The corresponding reactions with alkyl propargyl ethers also
produced diiron complexes containing pentadienyl moieties with an
alkoxycarbonyl group via alkoxy migration with CO insertion. The migration
process via C–N or C–O bond cleavage could be related
to the coordination ability of N or O in the propargyl compounds.