Modulation of S‐Centered Reactivity: Impact of Terminal Ligands on Alkynyl Addition in [Fe₂(μ‐S₂)(CO)₄L₂] Complexes

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