Iron acetyl complex

The a-alkoxy-substituted iron-acyl complex 8 is prepared by oxidation of the enolate prepared from iron-acetyl complex 6 and subsequent etherification12. 

I.3.4.2.5.I.2. Aldol Additions of Enolates of Chiral Iron-Acetyl Complexes... 

We synthesized cationic y2-acetyl compounds 28,25 by combining iron acetyl complexes CpFe(C0)L(C0CH3) (g7) [L=C0,PPh3] with a coordinatively unsaturated (16-electron) metal carbonyl salt CpM(CO)n+[M=Fe,n=2 M=Mo,n=3], as indicated in Scheme 5. Thus... 

FIGURE 15. Chiral iron acetyl complex A557 and chromium Fischer carbene complexes B and C558 as chiral acetate equivalents... 

Preparative Methods by ring-closure of 3-bromobutyric acid with Sodium Carbonate, or by hydrogenation of Diketene. The optically active forms are obtained in the same manner starting from (J )- or (,S)-3-bromobutyric acid, which may be resolved with the (5) form of I-(I-Naphthyl)ethylamine Asymmetric aldol condensation using an enantiopure iron acetyl complex followed by cyclization, or asymmetric hydrogenation of diketene catalyzed by a chiral ruthenium complex, also gives the optically active p-lactone. 

An interesting metal effect was observed in the aldol condensations of the enolate derived from the iron acetyl complex (r)"-C HdFe(CO)(PPhd(COMe) with aldehydes [56,57]. Although the lithium enolate did not show any selectivity, the corresponding aluminum enolate by transmetalation with Et.AlCl exhibited exceptionally high diastereoselectivity (>99% de). The resultant P-hydroxy acyl complexes are transformed to P-hydroxy acids on decomplexation with Br.. 

Attig, T. G., Wojcicki, A., Stereospecificity at Iron Center of Decarhonylation of an Iron Acetyl Complex, J. Organomet. Chem. 1974, 82, 397 415. 

The resolution of a racemic iron acetyl complex was achieved by Davies and Becker by its transformation into a 1 1 mixture of diastereoisomeric sulfides (67a) and (67b) [158]. Oxidation by mCPBA operates selectively on one diastereoisomer (because of a suitably located hydroxy group). The sulfoxide (68) was easily separated from sulfide (67b) and desulfurized to give the desired target. This a case of kinetic resolution of an equimolar mixture of diastereoisomers. 

In the presence of Et2AlCl the lithium enolate derived from the iron acetyl complex [(C H )Fe(CO)(PPh )C0Me] discriminates between... 

Iron Acetyl complexes are available at special introductory prices, as listed below. 

Add anhydrous lithium chloride (90 mg, 2.12 mmol) and racemic iron acetyl complex 1 (643 mg, 1.42 mmol) to the flask or Schlenk. These compounds should be added rapidly against a gentle stream of nitrogen after removal of the septum, which should be replaced immediately. 

Scheme 4.64 Acetate aldol addition with Iron acetyl complex 124b via Davies-Liebeskind enolates.

The procedure was also extended to the analogous propionyl and benzy-loxyacetyl iron complexes. Although the preparation of enantiomeric iron acetyl complexes (R)- and (S )-124b is Icnown and the reagent became even commercially available under both enantiomeric forms, it was nevertheless used as racemate. It seems that the immolative character of the aldol additions based on Davies-Liebeskind enolates prevented wider application in larger scale [140]. 

Isopropyl l//-l,2-diazepine-l-carboxylate similarly gives tricarbonyl(4-7t/-l-isopropoxycar-bonyl-l//-1,2-diazepine)ironin45% yield (mp 106"C)and l-acetyl-3-methyl-l//-l,2-diazepine gives the corresponding iron tricarbonyl complex in 92% yield (mp 110 C).77... 

The aldol reaction of iron-acetyl enolates such as 1 with aldehydes creates a new stereogenic center at the (S-carbon of the product complexes. 

A powerful variation of the iron acetyl enolate aldol reaction utilizes the cnolate of complex 8 which bears a (pentafluorophenyl)diphenylphosphane ligand in place of the more usual triphenylphosphane47. The enolate species 9. prepared by treatment of 8 with lithium diiso-propylamide, reacts at — 78 °C with benzaldehyde to produce the aldol adduct 10 with a d.r. of 98.5 1.5. 

While iron(III) complexes of thiosemicarbazones with different functional groups involving have been prepared from 2-acetylpyridine, substitution on the ring has been more popular with thiosemicarbazones derived from 2-formylpyridine. The only thiosemicarbazones in which the 2-acetylpyridine ring has been substituted are 15a and 15b, prepared from 6-methyl-2-acetyl-pyridine [120]. Both of these iron(III) complexes have rhombic spectra and values of g, are similar to those found for the 2-acetylpyridine thiosemicarbazones. Solution studies have been carried out on the iron(III) complex of 2,6-diacetylpyridine mono-thiosemicarbazone, but the solid complex was not isolated [143]. 

Further analysis of the spectral data for the P2"acetyl compounds 28 and 29 (Table 1) also indicates that the positive charge is distributed over both metal centers. The electronic environment of the C-bonded iron of 28 and 29 clearly lies intermediate between that of the starting acetyl complex and of the a-alkoxy-alkylidene compounds. Similarly the acetyl complexes provide more electron density to CpFe(CO)2+ within 28 than does acetone or THF within CpFe(C0)2Li+ [L =acetone, THF]. 

Ferrichrome was the first siderophore to be isolated and characterized from the fungi Ustilago sphaerogena in 1952. It is a cyclic hexapeptide with the sequence cycto[(Gly)3-(Al -acetyl-Af -hydroxy-L-ornithine)3] (1) . The biologically active ferrichromes form iron(ni) complexes with a left-handed A-cis helical twist. 

F,SCH, Methanesulfonic acid, trifluoro-iridium, manganese and rhenium complexes, 26 114, 115, 120 platinum complex, 26 126 OiFeCgH, Iron, acetyl dicarbonyl (if -cyclopentadienyl)-, 26 239 0,FeN2C2 Hll(, Iron, tricarbonylbis(2-isocy-ano-l,3-dimethylbenzene)-, 26 54 0.iMoNaCHH5-2 C4H ,02, Molybdate 1 -), tricarbonyl(T) -cyclopentadienyl)-sodium, compd. with 1,2-dimethoxy-ethane-(l 2), 26 343 0,NaWC H5-2 C4H ,02, Tungstate(l -), tricarbonyl(ris-cyclopentadienyl)-... 

The reactivity of five-membered rings with one heteroatom to electrophilic reagents has been quantitatively compared. Table 1 shows that the rates of substitution for (a) formylation by phosgene and V,iV-dimethylformamide, (b) acetylation by acetic anhydride and tin(IV) chloride, and (c) trifluoroacetylation with trifluoroacetic anhydride (71AHC(13)235) are all in the sequence furan > tellurophene > selenophene > thiophene. Pyrrole is still more reactive as shown by the rate for trifluoroacetylation, by the relative rates of bromination of the 2-methoxycarbonyl derivatives (pyrrole > furan > selenophene > thiophene), and by the rate data on the reaction of the iron tricarbonyl-complexed carbocation [C6H7Fe(CO)3]+ (Scheme 5) (2-methylindole ss V-methylindole > indole > pyrrole > furan > thiophene (73CC540)). 

Quantitative relative partial rate factors for acetylation of several of these iron-diene complexes were also obtained and are summarized in Scheme 5.1516... 

Bis(phosphoranimine) ligands, chromium complexes, 5, 359 Bis(pinacolato)diboranes activated alkene additions, 10, 731—732 for alkyl group functionalization, 10, 110 alkyne additions, 10, 728 allene additions, 10, 730 carbenoid additions, 10, 733 diazoalkane additions, 10, 733 imine additions, 10, 733 methylenecyclopropane additions, 10, 733 Bisporphyrins, in organometallic synthesis, 1, 71 Bis(pyrazol-l-yl)borane acetyl complexes, with iron, 6, 88 Bis(pyrazolyl)borates, in platinum(II) complexes, 8, 503 Bispyrazolyl-methane rhodium complex, preparation, 7, 185 Bis(pyrazolyl)methanes, in platinum(II) complexes, 8, 503 Bis(3-pyrazolyl)nickel complexes, preparation, 8, 80-81 Bis(2-pyridyl)amines... 

Smith MC, Barclay JE, Cramer SP, Davies SC, Gu W-W, Hughes DL, Longhurst S, Evans DJ (2002) Nickel-iron-sulfur complexes approaching structural analogues of the active sites of NiFe-hydrogenase and carbon monoxide dehydrogenase/acetyl-CoA synthase. Dalton Trans. 2641-2647... 

By reaction of cationic carbonyl complexes with lithium carbanions, neutral acyl complexes are prepared. Whereas treatment of [> -CpFe(CO)3]BF4 with (a) PhLi gives the expected > -CpFe(CO)2 [C(0)Ph] in 80% yield, with (b) MeLi only traces of > -CpFe(CO)2 [C(0)Me] can be detected . This complex and other phosphane-substituted acyl compounds of the type f -CpM(CO)L[C(0)Me] [M = Fe, Ru L = CO, PPh3, P(hex)j], as well as >/ -CpMo(CO)2P(hex)3[C(0)Me] (prepared by different routes), are protonated with and alkylated with [R3 0]BF4 reversibly, yielding cationic hydroxy- and alkoxy(methyl)carbene complexes, respectively . The formation of the ( + )- and ( —)-acetyl complex / -CpFe(C0)(PPh3)[C(0)Me] from the ( + )-and ( —)-conformers of optically active > -CpFe(C0XPPh3)[C(0)0-menthyl] and MeLi occurs with inversion of configuration at the asymmetric iron atom . 

One final comment relating to the aromaticity of the cyclobutadiene ligand concerns the orientation effect of substituents towards introduction of a second substituent. To date, the only reaction bearing on this question which has been performed is the acetylation of methylcyclobutadiene -Fe(CO)3 (XVIII), which was prepared by reducing the chloromethyl complex (IX). Acetylation of Complex XVIII produces a mixture of 2-and 3-acetyl-1-methylcyclobutadiene-iron tricarbonyl complexes with the latter isomer (XIX) predominating ( 2 1). This is not the orientation... 

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