σ-Bonded organometallics of iron and their facile conversion into π complexes

699-701The metal carbonylate anion, Na[Fe(η5-C5H5)(CO)] reacts at room temperature with halogeno organic ligands 1,3,5-tris(bromomethyl)benzene and 1,2,4,5-tetrakis-(bromomethyl)benzene to give the complexes 1,3,5-tris- (σ-methylene) benzene {tris(η5-cyciopentadienyl)hexacarbonyliron} (1) and 1,2,4,5-tetrakis(σ-methylene) benzene {tetrakis(η5-cyclopentadienyl) octacarbonyliron} (3). The complex (1) undergoes thermal transformation to the corresponding π complex whereas, complex (3) does not due to the 18-electron rule formalism