Iron carbonyls, reaction with thiophenes

Although C-S bond cleavage reactions between thiophenes and osmium clusters have not been observed, selenophene and tellurophene undergo ring opening reactions with [Os3(CO)io(NCMe)2] to give complexes 28a and 28b (Scheme T). " It is likely that the sulfur-extrusion reactions of iron and ruthenium carbonyl clusters with thiophenes proceed via ring-opened intermediates of this type. 

In addition to benzene and naphthalene derivatives, heteroaromatic compounds such as ferrocene[232, furan, thiophene, selenophene[233,234], and cyclobutadiene iron carbonyl complexpSS] react with alkenes to give vinyl heterocydes. The ease of the reaction of styrene with sub.stituted benzenes to give stilbene derivatives 260 increases in the order benzene < naphthalene < ferrocene < furan. The effect of substituents in this reaction is similar to that in the electrophilic aromatic substitution reactions[236]. 

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. ... 

The reactions of a,a -dibromoketones with iron carbonyls generate oxyallyliron complexes (75). These undergo cycloaddition with cyclopentadiene and furan, but with thiophene only products of electrophilic attack are obtained (78JA1765). Thus the oxyallyliron complex (75 R = Me R = H) reacts with thiophene to produce (76) in 37% yield. 

The pyrolysis of 3,8-bis(TMS)-l,2,5,6-tetrathiocane (47) was studied by pulse pyrolytic GC/MS. Compound (47) undergoes thermal decomposition via two mechanisms. The first pathway involves the formation of S2 and trimethylvinylsilane, which reacts further to give CSj, SiS2, and lower alkanes. The second pathway involves loss of three sulfur atoms to form TMS-substituted thiophenes <85JOM(289)23l>. Compound (47) also undergoes reaction with Fc3(CO)i2 to give a variety of sulfur-iron carbonyl complexes <86ZOK1540>. 

Thiophene has been reported to react with Fe(CO)s to produce a material described as thiophene-iron dicarbonyl 52). However, a complex having very similar properties to this substance and also obtained from the reaction of thiophene and Fe(CO)s or Fe3(CO)i2 was found not to contain sulfur (74) and the existence of thiophene-iron dicarbonyl is questionable. The material which does not contain sulfur is found to be identical to one of the products obtained upon reaction of acetylene with iron carbonyl, for which the binuclear structure (LVIII) has been proposed 38, 54, 75). 

If icon pentacarbonyl was present in the hydroformylation reaction mixture too, a mixed complex, COjFe(CO) S was formed in good yield (4). The tendency of formation of this very stable complex is so strong, that even thiophene is easily desulfurised under such conditions, a reaction, which is not significant with cobalt carbonyl alone. Even the iron orginating from a small corrosion of the walls of the reaction vessel leads to the predominant formation of this complex. 

---