Thiopheneacetylene (RC≡CH; R=3-Th, 2-Th; Th=C 4 H 3 S) adds across the Se-Se bond of (CO) 6 Fe 2 (μ-Se 2 ) at room temperature in methanol solvent containing sodium acetate to yield the adduct (CO) 6 Fe 2 {μ-SeC(H) C(R)Se} (R=3-Th (1); 2-Th (3)) and the double butterfly complex [{(CO) 6 Fe 2 Se 2 } 2 {μ-C(H)-C(R)}] (R=3-Th (2); 2-Th (4)). Compounds 1-4 were characterized by spectroscopic techniques (IR and 1 H-, 1 3 C- and 7 7 Se-NMR) and their composition confirmed by elemental analysis. Structures of 2 and 4 were further confirmed by single-crystal X-ray diffraction study.