A chalcogen-stabilized cluster containing a s-trans-1,3-diene ligand: Synthesis and structural characterization of{(CO) <inf>6</inf>Fe<inf>2</inf>Se<inf>2</inf>}<inf>2</inf>(μ-s-trans-C<inf>4</inf>H<inf>2</inf>)

Reaction of (CO)6Fe2(μ-Se)2 with HC≡CC≡CR (R = SiMe3 or SnnBu3) at room temperature in methanol containing sodium acetate yielded the unexpected product {(CO)6Fe2Se2}2(μ-s-trans-C4H2) in which a 1,3-butadiene ligand is coordinated to the Fe2Se2 core in a trans conformation as determined by a single-crystal X-ray diffraction studies. The complex was also obtained with a low yield by reaction of (CO)6Fe2(μ-Se)2 with HC≡CC≡CH under similar conditions.