Iron carbonyl hydrides, isomerization

The mechanism for homogeneous hydrogenation of methyl linoleate by Fe(CO)s based on kinetic evidences and radioactive tracers involves monoene- and diene-Fe(CO)4 and diene-Fe(CO)3 complexes as important intermediates. Contrary to our previous postulate (7) the free conjugated diene is only a minor intermediate. Confirmatory evidence is needed for the occurrence of oleate- and linoleate-Fe(CO)4 complexes during hydrogenation and isomerization with Fe(CO)r>. Also, the species of iron carbonyl hydrides formed during hydrogenation should be elucidated. 

The Fe3(CO)i2-catalyzed isomerization of 3-ethyl-l-pentene-3di gives 3-ethyl-2-pentene in which the deuterim label is randomly scrambled among the three methyl groups without loss of deuterium . The recovered 1-olefin also shows rapid random scrambling. These experiments demonstrate the intermediacy of w-allyl iron carbonyl hydrides and indicate Aat multiple addition-eliminations proceed before decomplexation of the catalyst occurs as... 

Iron carbonyls serve as catalysts for the isomerization of allylic alcohols to saturated carbonyl complexes as well as the conversion of allylic alcohols and formaldehyde to aldols. These processes were examined theoretically and the authors proposed that intermediate Fe(CO>3 was responsible for converting coordinated allyl alcohol into coordinated enol via two successive 1,3-hydride shifts. Several pathways for the subsequent reaction with formaldehyde were examined, but the most favorable involved direct attack of H2CO on the decomplexed enol. ... 

Cyclododecene may be prepared from 1,5,9-cyclododecatriene by the catalytic reduction with Raney nickel and hydrogen diluted with nitrogen, with nickel sulfide on alumina, with cobalt, iron, or nickel in the presence of thiophene, with palladium on charcoal, with palladimn chloride in the presence of water, with palladium on barium sulfate, with cobalt acetate in the presence of cobalt carbonyl, and with cobalt carbonyl and tri- -butyl phosphine. It may also be obtained from the triene by reduction with lithium and ethylamine, by disproportionation, - by epoxidation followed by isomerization to a ketone and WoliT-Kishner reduction, and from cyclododecanone by the reaction of its hydrazone with sodium hydride. ... 

Ill) Iron and Ruthenium. w-Allyliron complexes are not readily prepared directly from olefins by cleavage of an allylic C—H bond, but Jt-allylhydridoiron complexes are intermediates in olefin isomerization catalyzed by Fe(0) carbonyl complexes ". The intermediate 7i-allyliron hydride complexes formed are too reactive to be isolated and undergo a fast reductive elimination to give the isomerized or the starting olefin ... 

Numerous catalysts that are used for hydrogenation or hydroformyla-tion are also active isomerization catalysts. These catalysts require the presence of hydrogen to be activated, probably to form a metal hydride. Carbonyls of cobalt, iron, and osmium are activated in this manner and effect hydrogen shifts. 

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