Nucleophilic Attack and Structural Rearrangements in Some Iron Carbonyl Cluster Carbides. Syntheses, Structures, and Reactions of the Tetrahedral Four-Iron Clusters 3-COCH3)>- and -

Article abstract of DOI:10.1021/ja00385a010

The reaction of the four-iron butterfly compound ^2- with the strong carbocation reagent CH3SO3CF3 leads to alkylation of the carbide carbon and structural rearrangement of the metal framework to produce a tetrahedral ethyne compound, 3-CCH3)>^-.The rearrangement is readily explained by the cluster valence electron count.The tetrahedral carbonyl anion 3-CO)>^2- in the presence of CH3SO3CF3 is alkylated on the oxygen of a trihapto carbonyl to produce 3-COCH3)>^-, in which the tetrahedral iron array is retained.In this case, alkylation does not change the formal count of electrons available for cluster bonding and therefore does not change the geometry of the four-iron array.There is, however, an inductive electron demand imposed on the cluster by O-alkylation, and this appears to be responsible for the shift of ancillary semibridging CO ligands into terminal positions.