Iron complex

Tetrachloroferrates(III) are high spin complexes too (d5-e2t23, five unpaired electrons). For example, [H-TMPP][FeUICl4] has juefr = 

The tetracoordinated complexes of iron can also assume planar (or pseudoplanar) geometry. Typical examples are the Fe(II) complexes of the already discussed Schiff bases A,A -ethylenebis(salicylideneimine), salen, and A,./V -disalicylidene- 3-phenylenediamine, saloph. 

It has a magnetic moment of 5.22 //B, which testifies a high spin (d6-e 3 d2a[l, four unpaired electrons) complex. [Fe(saldpt)] in dmso solution also displays a reversible Fe(II)/Fe(III) oxidation (E° = -0.29 V).96 

Also in this case, its high spin nature is revealed by the magnetic moment 5.34 /rB (Fe(II) d V2 1, four unpaired electrons). 

These Fe(II) complexes are low spin (d6-t2g6), as deducible from their negligible magnetic moment = 0.5 Pb)- In acetonitrile solution they display a chemically reversible Fe(II)/Fe(III) oxidation. It must be taken into account that in acetonitrile solution they possess an octahedral 

Non-conjugated dienes isomerize during complexation to afford tricarbonyliron-coordinated conjugated dienes. This isomerization has been applied to a wide range of substituted cyclohexa-1,4-dienes available by Birch reduction from aromatic 

Because of the high lability of the reagents described above, (T 4-l-azabuta-l,3-dienejtricarbonyliron complexes have been developed as alternative tricarbonyliron transfer reagents. They are best prepared by an ultrasound-promoted reaction of 1-azabuta-l,3-dienes with nonacarbonyldiiron in tetrahydrofuran at room temperature. Using (ri4-l-azabuta-l,3-diene)tricarbonyliron complexes the transfer of the tricarbonyliron unit proceeds in refluxing tetrahydrofuran in high yields [55a,b]. 

The catalytic system described above has been further developed to an asymmetric catalytic complexation of prochiral 1,3-dienes (99% yield, up to 86% ee) using an optically active camphor-derived 1-azabutadiene ligand [56]. This method provides for the first time planar-chiral transition metal 7t-complexes by asymmetric catalysis. 

Cyclohexadienylium-tricarbonyliron complexes represent the most versatile iron complexes applied as building blocks in synthetic organic chemistry. Because of their positive charge, a large variety of nucleophiles undergo nucleophilic attack at the 

The construction of the carbazole framework is completed by an iron-mediated oxidative cyclization which proceeds via an initial single electron transfer to generate a 17-electron radical cation intermediate. Iron-mediated oxidative 

Even if the field of bi- and polyferrocenes deserves a review paper by itself [78], we would like to recall here the most simple compound, i.e. biferrocenyl, the crystal structure of which is shown in Fig. 7-22 [79], 

The two ferrocenyl units assume a trans disposition. In each ferrocenyl fragment, the cyclopentadienyl rings are neither eclipsed nor staggered and nearly parallel. The two linked rings are coplanar. 

As shown in Fig. 7-23, in CH2Cl2-MeCN solution biferrocenyl undergoes two distinct one-electron steps, which are reversible in character. 

Removal of the first electron occurs at E° = -1-0.31 V, which is lower than that of ferrocene (E° = 4-0.40 V) removal of the second electron occurs at = 4- 0.65 V [80]. As expected, the ferrocenyl substituent is more electron-donating than the hydrogen atom. 

In MeCN solution (j) -C5H5)Fe j) -C5H4CH2[Fe(CO)2(t -C5H5)] exhibits an initial irreversible oxidation centered on the iron-carbonyl fragment ( p se -I- 0.3 V) and a second reversible anodic process centered on the ferrocenyl fragment ( ° -1-0.5 V) [81]. Qualitatively similar behavior is displayed by ( j -C5H5)Fe 7 - 

CH2Cl2-MeCN solution. Scan rate 0.2 Vs (reproduced by permission of the American Chemical 

The catalysts 153-155 shtwTi in Table 9.7 have been used for polymerizations of acrylates and methacrylates and S. The catalyst 155 used in conjunction with an iodo compound initiator has also been employed for VAc polymerization. Catalytic chain transfer (Section 6.2,5) occurs in competition with halogen atom transfer with some catalysts. 

Catalyst Staicture Monomer Catalyst Structure Monomer 

Polymerizations of S and MMA with in situ catalyst formation have also been carried out. Matyjaszewski et reported on the use of FeBrn together with various ligands such as P(C4H5)3, N(C4H4)3 and 133 alone or in combination. The use of diearboxylie acid (iminodiacetic acid, isophthalie aeid) and methanimine ligands for MMA polymerization has also been reported. 

Walues of ee were determined by HPLC using a Chiralcel OD column except for entries 9 and 10, which were determined by H NMR in presence of (R)-(—)-2,2,2-trifluoro-1-(9-anthryl) ethanol. 

This Cj symmetrical complex was used as a catalyst with iodosobenzene as oxidant in presence of 1-methylimidazole as an axial ligand. The turnover number is dependent on the substrates and fluctuates between 55 and 290. The enantiomeric excess is noticeably improved to 73% (31% without this reagent) for 

Groves and colleagues reported similar results [112] with a binaphthyl iron(III) tetraphenylporphyrin as a catalyst (0.1 mol% equiv) and iodosobenzene as oxidant. Prochiral alkyl sulfide substrates gave sulfoxides in 14% to 48% ee with some overoxidation to sulfones (8%). 

An iron porphyrin bearing (5)-naphthylpropionic amide groups has been synthesized by Zhou et al. [113]. With 10% of catalyst, methyl phenyl sulfide was oxidized in 94% yield, but with only 8% ee. The addition of imidazole increased the optical purity to 15%, but the yield of the reaction decreased to 79%. 

In an analogous approach, the effect of imidazole was also observed by Inoue et al. [114]. When alkyl aryl sulfides were oxidized with a novel iron porphyrin catalyst (52) (0.2 mol% equiv), the reaction proceeded enantioselectively under appropriate conditions. Iodosobenzene was used as oxidant in dichloromethane at -43°C. The turnover number increases to 142, and an ee of 73% was obtained in the presence of a 100 to 600 molar ratio of imidazole to catalyst for the synthesis of (5)-methoxymethyl phenyl sulfoxide. In the absence of imidazole, the enantioselectivity disappeared, giving the racemic sulfoxide. 

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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). 

COORDINATIONCOMPOUNDS](Vol7) cis-Tetracaibonyl (2-3-h2-maleic acid) iron complex... 

Chiral diene—iron tricarbonyl complexes were acylated using aluminum chloride to give acylated diene—iron complexes with high enantiomeric purity (>96% ee). For example, /ra/ j -piperjdene—iron tricarbonyl reacted with acyl haUdes under Friedel-Crafts conditions to give l-acyl-l,3-pentadiene—iron tricarbonyl complex without any racemization. These complexes can be converted to a variety of enantiomericaHy pure tertiary alcohols (180). 

Aminoboranes have been used as ligands in complexes with transition metals (66) in one instance giving a rare example of two-coordinate, non-t/ transition-metal complexes. The molecular stmcture of the iron complex Fe[N(Mes)B(Mes)2]2 where Mes = is shown in Figure 1. The... 

Other Reactions. Due to the highly reactive conjugated double bonds, butadiene can undergo many reactions with transition metals to form organometaHic complexes. For instance, iron pentacarbonyl reacts with butadiene to produce the tricarbonyl iron complex (10) (226). This and many other organometaHic complexes have been covered (227). 

Cyclopentadiene itself has been used as a feedstock for carbon fiber manufacture (76). Cyclopentadiene is also a component of supported metallocene—alumoxane polymerization catalysts in the preparation of syndiotactic polyolefins (77), as a nickel or iron complex in the production of methanol and ethanol from synthesis gas (78), and as Group VIII metal complexes for the production of acetaldehyde from methanol and synthesis gas (79). 

The stmcture of the blue material was not elucidated until 1934, when it was shown to be the iron complex of (67). The new material was christened phthalocyanine [574-93-6] reflecting both its origin from phthaUc anhydride and its beautihil blue color (like cyanine dyes). A year later the stmcture was confirmed by one of the first uses of x-ray crystallography. 

The only nitroso dyes important commercially are the iron complexes of sulfonated l-nitroso-2-naphthol, eg. Cl Acid Green 1 [57813-94-2] (78) (Cl 10020) these inexpensive colorants are used mainly for coloring paper. 

Diels-Alder reactions, 4, 842 flash vapour phase pyrolysis, 4, 846 reactions with 6-dimethylaminofuKenov, 4, 844 reactions with JV,n-diphenylnitrone, 4, 841 reactions with mesitonitrile oxide, 4, 841 structure, 4, 715, 725 synthesis, 4, 725, 767-769, 930 theoretical methods, 4, 3 tricarbonyl iron complexes, 4, 847 dipole moments, 4, 716 n-directing effect, 4, 44 2,5-disubstituted synthesis, 4, 116-117 from l,3-dithiolylium-4-olates, 6, 826 electrocyclization, 4, 748-750 electron bombardment, 4, 739 electronic deformation, 4, 722-723 electronic structure, 4, 715 electrophilic substitution, 4, 43, 44, 717-719, 751 directing effects, 4, 752-753 fluorescence spectra, 4, 735-736 fluorinated derivatives, 4, 679 H NMR, 4, 731 Friedel-Crafts acylation, 4, 777 with fused six-membered heterocyclic rings, 4, 973-1036 fused small rings structure, 4, 720-721 gas phase UV spectrum, 4, 734 H NMR, 4, 7, 728-731, 939 solvent effects, 4, 730 substituent constants, 4, 731 halo... 

The following compounds have been obtained from thiete 1,1-dioxide Substituted cycloheptatrienes, benzyl o-toluenethiosulfinate, pyrazoles, - naphthothiete 1,1-dioxides, and 3-subst1tuted thietane 1,1-dioxides.It is a dienophile in Diels-Alder reactions and undergoes cycloadditions with enamines, dienamines, and ynamines. Thiete 1,1-dioxide is a source of the novel intermediate, vinylsulfene (CH2=CHCH=SQ2). which undergoes cyclo-additions to strained olefinic double bonds, reacts with phenol to give allyl sulfonate derivatives or cyclizes unimolecularly to give an unsaturated sultene. - Platinum and iron complexes of thiete 1,1-dioxide have been reported. 

ALKYLATION OF DIMEDONE WITH A TRICARBONYL(DIENE)IRON COMPLEX TRlCARBONYL[2-[(2,3,4,5-t))-4-METHOXY 2,4 CYCLOHEXADUEN-l-YLJ-5,5-DIMETHYL-l,3-CYCLOHEXANEDIONE]IRON... 

The smallest member, cyclobutadiene, was the objective of attempted synthesis for many years. The first success was aehieved when cyclobutadiene released from a stable iron complex was trapped with various reagents. ... 

A model similar to that of the iron complex 31 was proposed for the cobalt species synthesized as a result of co-condensation of cobalt vapors with pyrrole in vacuum. A frozen matrix formed is subsequently warmed to room temperature (89JA3881). An oligomer or a polymer results, in which a- and ir-donor functions are realized simultaneously. The model proposed differs from that for the iron pyrrolyl complex by inclusion of the Co—Co bonds to attain the 18-electron configuration. 

Syntheses of heterocycles, among them carbazole alkaloids, with participation of tricarbonyl(Ti -diene)iron complexes 99CSR151. 

As well as organic diiral auxiliaries, organometallic fragments have found some lonjugate addition reactions. PatLiciilarly note-aliyl complexes [69], diiral iron complexes [70], and planar diiral aretie diromium species [71]. 

The UV stabilizing action of nickel and iron complexes (e.g., NiDRC and FeDRC) is strongly concentra-... 

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