Unexpected Carbon–Carbon Bond Cleavage in the Reactions of the Pentagonal Bipyramidal Cluster Fe3(CO)6(μ-CO)2[μ3-η4-{RCC(Et)C(Et)CR}] with Styrene. Synthesis and X-ray Structure of Fe3(CO)6[μ3-η4-{EtC2CR}]2 (R = CH3(=CH2))

Abstract

The thermal reactions of 2-methyl-1-hexen-3-yne [CH3CH2C≡CC(=CH2)CH3, metey] with Fe3(CO)12 have been studied: cluster opening or fragmentation and alkyne dimerization occur. Main products are the open triangular isomers [Fe3(CO)6(μ-CO)2{CH3(=CH2)CC(Et)C(Et)C(=CH2)CH3}] (complex 3a) and [Fe3(CO)6(μ-CO)2{C(Et)CCH3(=CH2)C(Et)CCH3(=CH2)}] (complex 3b). The structure and isomerism of the complexes has been confirmed by X-ray studies. The minor products of the reaction have been characterized by spectroscopic techniques. An attempt at exploiting the reactivity of the “free” C=C bonds of the coordinated ene-yne was made: complex 3a was reacted with styrene under thermal conditions. Unexpectedly considerable yields of the closed triangular cluster [Fe3(CO)6{EtC2C(=CH2)CH3}2] (complex 5) have been obtained. This behaviour had not been previously observed. The unprecedented structure of complex 5 has been confirmed with an X-ray study.