Unexpected carbon-carbon bond cleavage in the reactions of the pentagonal bipyramidal cluster Fe-3(CO)(6)(mu-CO)(2)[mu(3)-eta(4)-{RCC(Et)C(Et)CR}] with styrene. Synthesis and x-ray structure of Fe-3(CO)(6)[mu(3)-eta(4)-{EtC2CR}](2) (R = CH3(=CH2))

摘要

The thermal reactions of 2-methyl-1-hexen-3-yne [CH3CH2C equivalent to CC(=CH2)CH3, metey] with Fe-3(CO)(12) have been studied: cluster opening or fragmentation and alkyne dimerization occur. Main products are the open triangular isomers [Fe-3(CO)(6)(mu-CO)(2){CH3(=CH2)CC(Et)C(Et)C(=CH2)CH3}] (complex 3a) and [Fe-3(CO)(6)(mu-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 [Fe-3(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.