Reaction of mono- and dilithiated thiophene (a), bithiophene (b) and 2,5-dibromothiophene (c) with [Re₂(CO)₁₀] afforded, after subsequent alkylation with triethyloxonium tetrafluoroborate, tetra- and binuclear Fischer carbene complexes, [Re₂(CO)₉{C(OEt){C₄H₂S}_nX}], n = 1, X = H (1a); n = 2, X = H (1b); n = 1, X = Br (1c); n = 1, X = C(OEt)Re₂(CO)₉, (2a); n = 2, X = C(OEt)Re₂(CO)₉ (2b), as major products. The dirhenium acylate intermediates from this reaction not only gave the expected novel ethoxycarbene complexes with alkylation but after rhenium–rhenium bond breaking afforded a number of minor products. The ¹H NMR spectrum of the crude reaction mixture revealed the formation of four metal hydride complexes and aldehydes. Protonation with HBF₄ instead of alkylation with Et₃OBF₄ significantly increased the yields of the hydride complexes, which enabled the positive identification of three of these complexes. In addition to the known compounds [Re(CO)₅H] and [Re₃(CO)₁₄H] (3), a unique complex displaying a hydroxycarbene fragment connected to an acyl fragment via an O–H⋯O hydrogen bond and a Re⋯H⋯Re bond linking the two Re centers, [(μ-H){Re(CO)₄C(OH){C₄H₂S}_nH}{Re(CO)₄C(O){C₄H₂S}_nH}], n = 1 (4a) or n = 2 (4b), were isolated. The formation of thiophene aldehydes, H{C(O)}_m{C₄H₂S}_nC(O)H (m = 0 or 1 and n = 1 or 2), were observed and the novel monocarbene complexes with terminal aldehyde groups, [Re₂(CO)₉{C(OEt){C₄H₂S}_nC(O)H}], n = 1 (5a) and n = 2 (5b) could be isolated. A higher yield of 5b was obtained after stirring crystals of 2b in wet THF. The crystal structures of 1a, 2a, 4a and 5b are reported.