Organoirons reactions with

The iron slurries show exceptional reactivity toward oxidative addition reactions with carbon halogen bonds. In fact, the reaction with C.FcI is so exothermic that the slurry has to be cooled to 0 °C before the addition of C F L The reaction of iron with C F Br is also quite exothermic, hence, even for this addition, the iron slurry is cooled to about 0 ° C. The organoiron compound formed in the above reactions, solvated Fe(C.F )2, reacts with CO at room temperature and ambient pressure to yiela Fe(C,F3)2(CO)2(DMEL. 

The reaction with Fc3(CO)i2, however, results in the loss of tellurium and formation of tellurium-lfee organoiron complexes. Similar loss of tellurium has reported on the reaction with tellurophenes and benzotellurophenes. " ... 

A,ii, Cyclopentadienylirondicarbonyl (Fp) Compounds. A common organoiron reagent is cyclo-pentadienylbis(carbonyliron) (Fp, 711). " This derivative can be converted to an alkyl derivative (713, where R = alkyl) by reaction with an alkyl halide, or to the protio derivative (713, R = H) by reaction with an acid. The anionic reagent 712 is prepared by reaction of iron pentacarbonyl with the dimer of cyclopentadiene (710 - sec. 115.B) at 200°C to give the dimeric species 711. Treatment of 711 with base leads to loss of cyclopentadiene and formation of 712. A byproduct of this process is ferrocene (71 4) formed by extrusion of carbon monoxide from 711.595... 

A.iii. Sodium Tetracarbonyl Ferrate. An extremely useful organoiron reagent is sodium tetra-carbonyl ferrate [Na2Fe(CO)4], usually prepared by reduction of iron pentacarbonyl. The synthetic utility of this reagent lies in its ability to react with alkyl halides in a stepwise manner, including the reaction with two different alkyl halides, as reported independently by Cooke and by Collman and co-workers. - When sodium tetracarbonyl ferrate reacted with 1-bromooctane, a trigonal bipyramidal complex (715) was formed... 

Several important characteristics of this reaction are shown. First, the nucleophilic addition can be reversible if complex 736 is heated. Second, the complex can be decomposed by reaction with iodine (to give 737) or by protonolysis (with trifluoroacetic acid, TFA) to give cyclohexadiene derivative 738. The reagents used to remove the metal are similar to those used with organoiron complexes (sec. 8.9.A). 

Turning to carbonyls containing more than one metal atom, Johnson has proposed a new mechanism for the substitution reactions of metal-carbonyl dimers Corraine and Atwood have produced a number of papers dealing with carbonyl anions in reaction with carbonyl dimers. The thermodynamic and kinetic factors that control the reactions are also discussed 2. Heaton et al have discussed the electron-microscopy of transition-metal carbonyl clusters 25,26 Butler et al have published a comparison of photoacousdc, attenuated total reflection, and transmission infrared-spectra of crystalline organoiron(ll) carbonyl-complexes 27. 

The basic compounds of syntheses of organoiron compounds are two compounds of ferrocene and ironpentacarbonyl compounds. As many reactions have also been studied of these two compounds, first the author will describe reactions with these compounds and then describe cyclometalations polymerizations, catalytic reactions, etc. 

The reaction properties of organoiron compounds such as the isomerization (eq. (15.8)) and the reaction with protection of diene group (Scheme 15.8), have been used for organic syntheses [98,99]. Organoiron compounds are also used as various kinds of catalysts for example, for the water-gas-shift reaction (eq. (15.41) [99,100]), syntheses of carbodiimide (eq. (15.42) [99]), isomerization of allyl-... 

They also obtained organoiron complexes with isoprene and Fe(CO)s but the reaction apparently failed in the case of isobutylene. 

T " -Diene- and Tj -dienyliumiron complexes represent the most widely stoichiometrically applied organoiron species. They are rather stable and can be transformed into each other. The reactivity of the diene system as part of the (Ti" -diene)iron complex is altered. The electron density of the diene system is reduced due to 7t-donation to the metal center. Consequently, reactions with electrophiles are more... 

As mentioned earlier, the possible products of the -complexes include ring-opened structures. This includes isomer 181 and some of its derivatives, for example, 187,188,196,197, 203, and 204, as well as the products of interaction with organoiron, 180,191, and 194, and organocobalt, 199,200, and 201, compounds. They have already been discussed together with the variously characterized V-complexes. Examples of the ring-opening reactions based on the -q- and ri -species are given next. 

The reaction proceeds by an ET pathway giving the I9e organoiron radical cation and the organic radical R which couple in the cage after escape ofX. The cationic Fe1 intermediate is noted at low temperature by its characteristic purple color and the classical spectrum of Fe1 species with rhombic distortion (g = 2.091, 2.012, 2.003 at —140 °C in acetone) before collapse to the orange substituted cyclohexa-dienyl Fe11 complexes. 

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