The synthesis, and molecular and electronic structure of dodecacarbonyl(µ4-η2- prop-1-ene-1,1-diyl)tetrairon, Fe4(CO)12(µ4-η 2-CCHCH3)

Abstract

The µ ₄ -vinylidene cluster Fe ₄ (CO) ₁₂ (µ ₄ -η ² -C CHCH ₃ ) has been prepared by the sequential reaction of Fe ₄ (CO) ₁₂ [CC(CH ₃ )(OCH ₃ )], with lithium triethylhydroborate and trimethylsilyl trifluoromethanesulfonate. The cluster has an open butterfly arrangement of four iron atoms with the prop-1-ene-1,1-diyl ligand bound to all four iron atoms in a manner giving an axial CC bond, perpendicular to both the mutually perpendicular Fe–Fe vectors between the wingtip iron atoms (Fe _w ) and between the hinge iron atoms (Fe _h ). The vinylidene carbon atom lies below the Fe _w –Fe _w vector, essentially inside the Fe ₄ core. Molecular orbital calculations using the Fenske–Hall method were carried out for the cluster, showing that the geometry of the Fe ₄ CCHCH ₃ fragment results from overlap between the formal CC double bond and the two Fe _w iron atoms. Comparisons are drawn between Fe ₄ (CO) ₁₂ (µ ₄ -η ² -C CHCH ₃ ) and other Fe ₄ vinylidene clusters.