Iron compounds Dicarbonyl

In a similar manner, Jt-allyl complexes of manganese, iron, and molybdenum carbonyls have been obtained from the corresponding metal carbonyl halides [5], In the case of the reaction of dicarbonyl(r 5-cyclopentadienyl)molybdenum bromide with allyl bromide, the c-allyl derivative is obtained in 75% yield in dichloromethane, but the Jt-allyl complex is the sole product (95%), when the reaction is conducted in a watenbenzene two-phase system. Similar solvent effects are observed in the corresponding reaction of the iron compound. As with the cobalt tetracarbonyl anion, it is... 

Jiang S, Agoston GE, Chen T, Cabal M-P, Turns E (1995) BF3 Et20-promoted allylation reactions of allyl(cyclopentadienyl)iron(II) dicarbonyl complexes with carbonyl compounds. Organometallics 14 4697 -709... 

For example, in a recent tutorial, Kettle and co-authors described the solid-state vibrational spectroscopy of bis(dicarbonyl-77-cyclopentadienyliron) [4]. Although it is well established, solid-state spectroscopy is given cursory treatment in standard physical chemistry textbooks. The iron compound makes an interesting case study because its cis and trans isomers crystallize in the same space group. Raman and infrared spectroscopy are given equal consideration in the discussion. 

A mechanistic study of acetophenone keto-enol tautomerism has been reported, and intramolecular and external factors determining the enol-enol equilibria in the cw-enol forms of 1,3-dicarbonyl compounds have been analysed. The effects of substituents, solvents, concentration, and temperature on the tautomerization of ethyl 3-oxobutyrate and its 2-alkyl derivatives have been studied, and the keto-enol tautomerism of mono-substituted phenylpyruvic acids has been investigated. Equilibrium constants have been measured for the keto-enol tautomers of 2-, 3- and 4-phenylacetylpyridines in aqueous solution. A procedure has been developed for the acylation of phosphoryl- and thiophosphoryl-acetonitriles under phase-transfer catalysis conditions, and the keto-enol tautomerism of the resulting phosphoryl(thiophosphoryl)-substituted acylacetonitriles has been studied. The equilibrium (388) (389) has been catalysed by acid, base and by iron(III). Whereas... 

With respect to the mechanism of the iron catalysis, the activity of FeCl3 -6H20 is closely related to its ability to give dionato chelate complexes 3 with [i-dicarbonyl compounds. Without prior deprotonation - even in Bronsted acidic media - these deeply colored iron complexes are instantly formed. With this property, Fe(III) is unique among all other transition metals, which require a stoichiometric amount of base for dionato complex formation. Known for over 100 years, the significant color of the complexes has been utilized for the detection of [i-oxo esters and [i-di ketones. 

Especially characteristic were the tricarbonyl derivatives M(CO)3L3 (L = amine, NH3, etc.), but tetra- and pentacarbonyl compounds were also discovered. Recently, even dicarbonyls M(CO)2(L—L)2 and fully substituted derivatives M(L—L)3 and M(L—L—L)2 (L—L = dipyridyl, o-phenanthroline L—L—L = tripyridyl) have been synthesized from the hexacarbonyls by my former co-worker H. Behrens (5). Monosubstituted derivatives of iron pentacarbonyl Fe(CO)4L (L = NH3, amines, etc.) have been identified relatively recently (6). 

Fig. 8 Iron-catalyzed coupling reactions of P-dicarbonyl compounds with ethers, sulfides or tertiary amines...

Li and coworkers published addition reactions of ethers, sulfides, or tertiary amines 40 to p-dicarbonyl compounds 39 (Fig. 8) [96]. Fe2(CO)9 proved to be the catalyst of choice and di-tert-butyl peroxide the optimal oxidant. a-Functionalized p-dicarbonyl compounds 41 were isolated in 52-98% yield. Although the details of the catalytic cycle remain unclear, it seems to be likely that the peroxide is reductively cleaved by the Fe(0) catalyst leading to an Fe(I) complex and a ferf-butoxyl radical, which abstracts the a-hydrogen atom of 40. Addition of the resulting radical to the free enol form of 39 or the corresponding iron enolate of 39 may subsequently occur. It remains unclear, however, whether the main catalytic reaction proceeds on an Fe(0)-Fe(I) oxidation stage or whether further oxidation of initially formed Fe(I) rather leads to an Fe(II) catalyst. This cannot be excluded,... 

Carbodiimides also add to metal carbon bonds in metalorganic compounds. For example, cyclopentadienyl iron dicarbonyl 286 affords [2-f2] cycloadducts 287 with diphenyl- and... 

To make the reactive fulleride compound KeCeo in the Fe-Ceo synthesis, fullerenes and a slight excess of potassium were sealed in a glass tube under vacuum and heated for approximately four days at 250 °C. Both solid-state NMR and Raman spectroscopy were employed to determine that the KeCeo compound was in fact synthesized. The KeCeo product was then reacted in an inert atmosphere with cyclopentadienyl-iron-dicarbonyl-iodide (CpFe(CO)2l) in tetrahydrofuran (THF) to form the complex. The recovered product was dried in an inert atmosphere. Manipulations of air-sensitive materials were carried out in a glove box or using standard Schlenk techniques. THF was distilled just prior to use from sodium benzophenone ketyl. Ceo was obtained from Aldrich, and CpFeCCOjol was obtained from Strew. 

It is interesting to compare the reaetion schemes for the titanium derivatives with these proposed for eyclopentadienyliron dicarbonyls. In both cases C5H5 transfer occurs. In the former case the electron-deficient compound is the substrate, in the latter case the substrate is the electron donor. Thus ligand transfer from the titanium is a nucleophilic substitution, whereas the similar reaction for the iron derivatives can be described in terms of electrophilic substitution. The latter conclusion is in agreement with the results of Cramer (S5), w ho has suggested that CO substitution by halogens in the above-mentioned iron eomplexes follows an electrophilic mechanism 218, 219). 

Epoxides. Reductive formation of epoxides from 1,2-dicarbonyl compounds with CifOAcjj is highly efficient. Thus, benzil is converted to irons-stilbene oxide in an aqueous DMF medium. 

Michael reactions. 1,3-Dicarbonyl compounds react with Michael acceptors in neat form with catalysis of iron(III) chloride hexahydrate at room temperature (19 examples, 46-l(X)%). An intramolecular version is also quite rewarding for the formation of a 7-membered ring. ... 

Use Chemical intermediate, organic synthesis (Diels-Alder reaction), starting material for synthetic prostaglandin, chlorinated insecticides, formation of sandwich compounds by chelation, e.g., cyclo-pentadienyl iron dicarbonyl dimer [C5H5Fe(CO)J2. 

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