The reactivity of complexes [Fe2(µ-S2)(CO)4L2] (L = CO (1), PPh3 (2)), with lithium alkynylide reagents generated in situ, was investigated. The behavior of the S2-bridge in these compounds depends on the substitution at the diiron core. The reaction with the hexacarbonyl derivative 1 leads to the formation of the 1,2-dithiolene bridged complex [Fe2(µ-SCH=C(R)S)(CO)6] (3R) while the molecule [Fe2(µ-SH)(µ-SC≡CR)(CO)4(PPh3)2] (5R), with an open butterfly structure, is isolated when reacting the disubstituted derivative 2. The disubstituted dithiolene complex [Fe2(µ-SCH=C(Ph)S)(CO)4(PPh3)2] (4Ph) can only be obtained by substitution of carbonyls with PPh3 in 3R. In the presence of piperidine, 5R isomerizes into the 1,1’-dithiolene bridged derivative 6Ph. The novel compounds 4-6 were synthesized and characterized by IR and NMR spectroscopies. X-ray crystallographic studies of the dithiolene complexes 3Ph-4Ph allowed their structural analysis.