NEW COMPLEXES WITH ETA4-TRIMETHYLENEMETHANE STRUCTURE SYNTHESIZED FROM SODIUM TETRACARBONYLFERRATE BY INSERTION OF ALLENE INTO METAL-CARBON BOND

The mechanism of formation of α,β-unsaturated ketones in the reaction of disodium tetracarbonylferrate, with an alkyl bromide and allene, is investigated; new intermediate complexes are isolated. In the anion resulting from insertion of allene into an ironacyl bond the negative charge is delocalised over the metallic center and the organic ligand and confirms an η4-trimethylenemethane type behaviour. Reactions with (CH3)3SiCl and proton yield neutral η4-trimethylenemethane complex. In the case of proton a subsequent sigmatropic shift yields a η4-heterodiene complexe. The anion is isolated as its ionic cristalline PPN+ salt. © 1979.