Iron complexes cyclopentadienyls

Alkenes in (alkene)dicarbonyl(T -cyclopentadienyl)iron(l+) cations react with carbon nucleophiles to form new C —C bonds (M. Rosenblum, 1974 A.J. Pearson, 1987). Tricarbon-yi(ri -cycIohexadienyI)iron(l-h) cations, prepared from the T] -l,3-cyclohexadiene complexes by hydride abstraction with tritylium cations, react similarly to give 5-substituted 1,3-cyclo-hexadienes, and neutral tricarbonyl(n -l,3-cyciohexadiene)iron complexes can be coupled with olefins by hydrogen transfer at > 140°C. These reactions proceed regio- and stereospecifically in the successive cyanide addition and spirocyclization at an optically pure N-allyl-N-phenyl-1,3-cyclohexadiene-l-carboxamide iron complex (A.J. Pearson, 1989). 

Alkylation of the anion 2 with iodomethane or other haloalkanes provides alkyldicarbonyl(t/5-cyclopentadienyl)iron complexes such as 53,0 (see also Houben-Weyl, Vol. 13/9a, p 209). Migratory insertion of carbon monoxide occurs on treatment with phosphanes or phosphites9 -11 (see also Houben-Weyl, Vol. d3/9a, p257) to provide chiral iron-acyl complexes such as 6. This is the most commonly used preparation of racemic chiral iron-acyl complexes. 

Decomplexation of some metal complexes calls for drastic conditions. This is true for (/7-arene)(/7-cyclopentadienyl)iron(II) hexafluorophosphates, [FeAr(Cp)][PF6] [54, 55]. Although their chemical decomplexation is known [55 a], the most widely used method is pyrolytic sublimation at high temperatures (>200 °C) [55 b]. To evaluate MW irradiation as the method of decomplexation of such iron complexes, Roberts et al. performed the reaction in the presence of graphite [54]. They discovered that the yield of the free ligand from the [Fe( -N-phenylcarbazole)( -Cp)][PF6] complex (43) depended on the kind (flakes or powder) and amount of graphite, and on the irradia-... 

Another example of a complex that obeys the 18-electron rule is ferrocene or bis(cyclopentadienyl) iron. The cyclopentadienyl anion is generated by the reaction of cydopentadiene with sodium, and ferrocene is obtained by the subsequent reaction with ferrous chloride,... 

The binuclear iron complexes (317) have been found to undergo a thermal rearrangement to afford the complexes (318), which were evidently formed via a metathesis between Si—Si and Fe—Fe bonds in (317). A similar rearrangement has been observed in a disilyl-bridged bis(cyclopentadienyl)tetracarbonyldiruthenium complex. Unprecedented and stable in — rf J7 -pentafulvadiene)dimthenium complexes (320) have been prepared" from a two-electron oxidation of frani -l,2-bis(mthenocenyl)ethylenes (319), and dimethyl analogues have been similarly obtained from trans- and cM-l,2-dimethyl-l,2-bis(ruthenocenyl)ethylenes. 

The compound cyclopentadienylcyclo-octatetraenecobalt is probably analogous to the compound cyclopentadienyl cyclopentadienecobalt (XXIV). The cyclo-octatetraene residue shows two proton resonance lines in the nmr spectrum (167) in contrast to that in the iron complex [Fe(CO)3(cyclo-octatetraene)] which shows only one proton resonance line (152, 180). 

Applying the pseudo-atom convention to the iron complex in Figure 8, the iodine atom is priority 1, the t1S-C5H3R2 ligand is priority number 2, the phosphorus atom is priority number 3, and carbon is priority number 4.15 When the iron is viewed from the side opposite the priority number 4, the sequence is 1,2,3 in the anticlockwise or 5 direction. The highest priority carbon in the cyclopentadienyl ligand, indicated by an asterisk, is designated with the R chirality symbol by application of the extended CIP sequence rule. 

Iron complexes with organic ligands are widely used as such reservoirs. For example, the stable 19-electron complex cyclopentadienyl benzene iron(I) is a clean electron reservoir that has a sufficiently negative oxidation potential and can be easily made, stored, and handled and can be weighed accurately (Alonso Astruc 2000). 

Iridium nanoparticles, preparation, 12, 82 Iridium(III) O-ligated complexes, preparation, 7, 315 Iridium polyhydrides, preparation and characteristics, 7, 405 Iridium pyrrolyl derivatives, reactivity, 7, 282 Iridium tetrahydrides, characteristics, 7, 407-408 Iridium trihydrides, preparation, 7, 405 Iridium vinylidenes, synthesis and characteristics, 7, 352 Iridium xyliphos complexes, properties, 7, 442 Iridoids, via Pauson-Khand reaction, 11, 360 Iron(arene) (cyclopentadienyl) cations, preparation and reactivity, 6, 166... 

The use of transition-metal arene complexes to facilitate nucleophilic aromatic substitution features in a route to derivatives of thiosalicylic acid and hence to thioxanthone. The cyclopentadienyl iron complex of 2-chlorobenzoic acid is converted into the benzamide prior to displacement of the chloride by thiophenoxide. Photolytic decom-plexation followed by directed remote metallation of the diaryl sulfide yielded the heterocycle (Scheme 207) <2000SL975>. 

A. R. Kudinov, A. A. Filchikov, P. V. Petrovskii, and M. I. Rybinskaya, 30-Electron Cationic Iron- and Cobalt-containing Triple-Decker Complexes with a Central Cyclopentadienyl Ligand. The First Synthesis of the Parent Triple-Decker Iron Complex with Cyclopentadienyl Ligands, [( 5-C5H5)Fe(p-jy jy-C5H5)Fe(jy5-C5H5)]PFg, Russ. Chem. Bull. 48, 1352-1355(1999). 

Aceto(carbonyl)cyclopentadienyl(triphenylphosphine)iron, CsHsFefCOKCOCH,)-[P(QHs)3] (1). Orange crystals, m.p. 145°, air stable. The chiral iron complex is prepared as a racemate by reaction of CsH5Fe(CO)2CH3 with P(C6H5)j. ... 

Many other iron complexes (t -alkyls, t -acyls, t -ynyls, cationic -alkenes, and carbenes) are ultimately erived from either sodium dicarbonyl(cyclopentadienyl)... 

There exist only a few scattered reports of ( -allyl)iron complexes lacking a cyclopentadienyl (see... 

Cyclopropanation reactions of nonheteroatom-stabilized carbenes have also been developed. The most versatile are the cationic iron carbenes that cyclopropanate alkenes with high stereospecificity under very mild reaction conditions. The cyclopropanation reagents are available from a number of iron complexes, for example, (9-alkylation of cyclopentadienyl dicarbonyliron alkyl or acyl complexes using Meerwein salts affords cationic Fischer carbenes. Cationic iron carbene intermediates can also be prepared by reaction of CpFe(CO)2 with aldehydes followed by treatment with TMS-chloride. Chiral intermolecular cyclopropanation using a chiral iron carbene having a complexed chromium tricarbonyl unit is observed (Scheme 61). 

Nesmeyanov, Volkenau et al. were the first to replace cyclopentadienyl with another ligand in ferrocene, preparing cyclopentadienyl-arene iron complexes by reaction of ferrocene with aromatic compounds in the presence of AICI3 255-259). 

A slight variation of the [3-I-2] cycloaddition approach <1977ICA(25)165> has also been employed for the diastereoselective synthesis of the corresponding anti- and ry -iron-substituted 1,2-dithiolane 1-oxides 243 from 237, as a source of electrophilic disulfur monoxide, and 7] -allyl iron complex 242 (Scheme 39). The method was also tested with cyclopentadienyl iron dicarbonyl crotonyl complex 244 when four diastereomers 245-248 were generated in modest yields (35%) <19980M5534>. 

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