Reactions of pentacarbonyliron

Condensation of [Fe(CO)5] onto CF3NO in a steel bomb, followed by warming to -20 C, resulted in the formation of COFj (indicated by the precipitation of diphenylurea on passage of the product gases into PhNH solution), in addition to CF, CO, FeF, N, CO, CF3N(0)=NCF3 and CFjN=NCF3 [650]. 

Small amounts of carbonyl difluoride are produced in the reaction of [Fe(CO)5] with tetrafluorohydrazine, NjF, in a steel bomb at about -10 C [594]. In contrast, NF3 and [Fe(CO)5] react only at temperatures above 100 C, and at 200 C a vigorous combination takes place with the formation of FN=NF, CO, and iron fluorides. Only a small quantity of COF 3 is formed, probably from the reaction of CO with FeF3 [594]. 

A vigorous reaction occurs between [Fe(CO)j] and SF5CI at room temperature, in which most of the carbonyl groups of the metal carbonyl are evolved as CO the remaining volatile material is composed of COF 3, COCI3, COCIF and COS [1345]. 

---

The light-induced reaction of pentacarbonyliron with oxepin or 2,7-dimethyloxepin results in the formation of small quantities (3-5 %) of a tricarbonyliron complex of the seven-mem-bered heterocycle.253,251 The main products are benzene (o-xylene) and phenol (2,6-dimethyl-phenol). When 1-benzoxepin is treated with pentacarbonyliron, the tricarbonyliron complex is obtained in 22% yield.254... 

A new class of boron compounds has been prepared by the reaction of pentacarbonyliron with dichloro(dimethylamino)borane to form (CO)4FeBN(CH3)2, a borylene complex.10 The mono- and dihaloamino-boranes can be prepared from the corresponding tris(amino)borane.11,12 Pyrolysis of the tris(primary amino)borane B(NHR)3 yields the borazine B3(NHR)3N3R3.3... 

Z. Iqbal, and T. C. Waddington, Liquid Hydrogen Chloride as an Ionizing Solvent. Protonation and Oxidation Reactions of Pentacarbonyliron, J. Chem. Soc. A, 1968, 2958-2961. 

The reaction of pentacarbonyliron with mono-olefins is known to give olefin-Fe(CO)4 complexes. These are probably intermediates in olefin isomerization, which generally occurs via a 1,3-hydrogen shift in arj -allylic intermediate (Scheme 10.3) [15]. 

Carbonyl insertion reactions are also carried out in the presence of pentacarbonyliron and are widely used for organic synthesis. Reaction of pentacarbonyliron with an organolithium followed by protonation gives an aldehyde derivative if a suitable alkyl halide is used in place of acid, a ketone is obtained (Scheme 10.5) [19]. 

Photochemical Reactions of Pentacarbonyliron with Ethene Cocondensed in Low Temperature Matrices. We have also studied the photochemical reactions of pentacarbonyliron with ethene cocondensed in the nitrogen matrix (22). While the formation of Fe(CO) (C2H ) in UV photolysis of Fe(C0)5 cocondensed with C2H in argon matrix was inferred from the IR spectra (23), no MWssbauer parameters were reported on this relatively unstable product. In order to elucidate the detailed mechanisms of photochemical reactions with cocondensed species, we have compared the products from the homogeneous cocondensed matrix with those from the stratified matrix where Fe(C0)j and C2H constituted separate... 

Iron.— The reaction of pentacarbonyliron with iodine is known to yield cis-[Fel2(CO)J. A study of the kinetics of the thermal reaction has been reported using stopped-flow techniques. The observed overall rate laws are interpreted... 

Alternatively, analogs of coordinatively unsaturated Fe(CO)4 species are provided by the reaction of pentacarbonyliron with trimethylamine N-oxide. Subsequent addition of an acetylene and final demetalation of the carbonyliron complexes by copper(II) chloride affords cyclobutenediones. ... 

Scheme 4-51. Synthesis of neutral (carbene)iron complexes by subsequent reaction of pentacarbonyliron with an organolithium compound and an alkyl fluorosulfonate.

Scheme 4-101. Formation of ( q -diene)iron complexes by reaction of pentacarbonyliron with 1,3-butadienes.

An asymmetric variant of this reaction can be carried out introducing a camphor-derived 1-azabutadiene ligand. Enantiomeric excess values of up to 86% can be achieved with this system to obtain planar chiral iron complexes. The photolytically induced reaction of pentacarbonyliron with prochiral cyclohexa-1,3-dienes can also be run enantioselectively using a chiral 1-azabutadiene catalyst. Quantitative yields and ee values up to 86% are possible under these conditions. Cyclic 1,4-dienes can also be complexed by pentacarbonyliron under concomitant rearrangement to the 1,3-diene... 

The first stable carbonylmetal-l//-azepine complex 25 (R = Et) was obtained by irradiating a mixture of ethyl 1 //-azepine-l-carboxylate (24, R = Et) and pentacarbonyliron(O) in tetrahy-drofuran (Method A).220 Hydrolysis of the complex with sodium methoxide gave azepine)tricarbonyliron(O) (26). Subsequently, the reaction of 24 with nonacarbonyldiiron(O) in warm benzene is reported to be a simpler and cleaner process.61 Both procedures fail, however, with alkyl-substituted l/Z-azepine-l-carboxylates. 

The catalytic complexation of cyclohexa-1,3-diene 2b is much superior to the classical procedures by direct reaction of the diene with pentacarbonyliron... 

Caution. Due to the toxic nature of pentacarbonyliron and to the evolution of highly toxic carbon monoxide (a colorless and odorless gas) and of highly flammable hydrogen, and also because of the toxic nature, bad odor, and risk of ignition of liquid phosphanes, these reactions should be performed in a well-ventilated hood and gloves should be worn. 

Pentacarbonyliron is a stable 18-electron complex of trigonal-bipyramidal geometry and represents the primary source of most organoiron complexes. Nonacarbonyldiiron is prepared in a photolytic reaction from pentacarbonyliron. Dodecacarbonyltriiron can be obtained from nonacarbonyldiiron by a thermal reaction. Both, nonacarbonyldiiron and dodecacarbonyltriiron, contain metal-metal bonds. They are slowly degraded to give pyrophoric iron and therefore should be handled with care. 

The reaction of two alkynes in the presence of pentacarbonyliron affords via a [2 + 2 + 1]-cycloaddition tricarbonyl(ri4-cyclopentadienone)iron complexes (Scheme 1.6) [5, 21-23]. An initial ligand exchange of two carbon monoxide ligands by two alkynes generating a tricarbonyl[bis(ri2-alkyne)]iron complex followed by an oxidative cyclization generates an intermediate ferracyclopentadiene. Insertion of carbon monoxide and subsequent reductive elimination lead to the tricarbonyl(T 4-cyclopentadienone)iron complex. These cyclopentadienone-iron complexes are fairly stable but can be demetallated to their corresponding free ligands (see Section 1.2.2). The [2 + 2 + l]-cycloaddition requires stoichiometric amounts of iron as the final 18-electron cyclopentadienone complex is stable under the reaction conditions. 

In a similar reaction, allylamines can be isomerized to afford enamines. Photochemical isomerization of the silylated allylamine in the presence of catalytic amounts of pentacarbonyliron provided exdusively the E-isomer of the enamine, whereas a thermally induced double bond shift provided a 4 1 mixture of the E- and Z-enamines (Scheme 1.38) [13],... 

The cationic manganese carbonyl derivative Mn(CO)4(phen)+ has been isolated as the Co(CO)4 and Mn(CO)5 salts (445) and the technetium derivatives Tc(CO)s(phen)X are also known. The color is a function of the halogen X, changing from colorless (X = Cl), through bright brown (X = Br), to brown (X = I) (374). The reaction of bipyridyl with pentacarbonyliron induces disproportionation (375) this can also occur when bis(l,3-cyclohexadiene)tetracarbonyldicobalt is the reactant. However, [L2(CO)4Co2] has been prepared 62). 

Bis(phosphine) derivatives of pentacarbonyliron are starting materials for the synthesis of several organometallic iron complexes. " Iron carbonyl phosphine complexes have attracted attention because of their relevance to photochemical catalysis of olefin hydrosilation. Though Fe(CO)3(PR3)2 complexes are used widely in organotransition metal chemistry, an efficient preparation of these compounds has not been reported. Clifford and Mukherjee describe two methods for the synthesis of tricarbonyl-bis(triphenyphosphine)iron(0). They report that direct reaction between Fe3(CO)j2 and triphenylphosphine in THF solvent gives a mixture of Fe(CO)3[P(C6Hs)3]2 (27%) and Fe(CO)4[P(C5H5)3] (34%). The second... 

A plausible mechanism for the reaction includes several organometallic species that are sensitive to reactive moieties elsewhere in the molecule. If a chloro, chloromethyl, or mesyloxymethyl substituent is attached vicinal to the 1,1 -dibromo moiety, efficient ring opening occurs prior to carbonylation and P,y- and y, -unsaturated acid derivatives are formed. Reductive carbonylation has also been achieved with 1,1-dibromocyclopropanes using an excess of pentacarbonyliron in dimethylformamide with added methanol or sodium methoxide, or cobalt(II) chloride and nickel(ll) cyanide under phase-transfer conditions in a carbon monoxide atmosphere. However, the yield of cyclopropanecarboxylic acid derivatives is low, and when pentacarbonyliron is used the amount of monobromides is fairly high. ... 

Pentacarbonyliron was prepared independently by Mond [2] and Berthelot [3] in 1891 by the direct reaction of finely ground iron with carbon monoxide. It is an air-stable liquid at room temperature which is used as a starting material for iron(O) chemistry (Scheme 10.1). Corresponding pentacarbonyls of ruthenium and osmium have found less application due to their facile decomposition to M3(CO)i2. Since Fe(CO)5 is commercially available and inexpensive, there is no need to synthesize it in the labora-... 

Enneacarbonyldiiron can be derived by the exposure of pentacarbonyliron to UV light and is also commercially available. It is an air-stable shiny yellow crystalline solid at room temperature. Fe2(CO)9 is less important as a precursor of iron complexes than as a reagent in organic synthesis. However, the following two reactions [13-14] are interesting because Fc2(CO)9 is used as a Fe(CO)4 synthon (Scheme 10.2). 

These reactions probably occur by the nucleophilic addition of the aryl anion to one of the CO groups of pentacarbonyliron followed by the addition of electrophiles. Pentacarbonyliron also causes carbonylation of electrophilic aryldiazonium salts [20]. 

Pentacarbonyliron is also capable of producing lactone from epoxides [21]. The reaction of dienemonoepoxide with Fe(CO)5 gives a p-TC-allylcarbonyliron complex. Unsaturated lactone is obtained after treatment of the allyliron intermediate with cerium (Scheme 10.6). 

Pentacarbonyliron releases its carbonyl ligands upon heating or exposure to UV light, and the resulting unsaturated species are known to react with various kinds of 1,3-dienes to form dieneiron tricarbonyl complexes. For example, (butadiene)tricar-bonyliron is prepared by the direct reaction of 1,3-butadiene with Fe(CO)5 at 130-140 °C in a closed system (eq (12)) [42]. 

Photolysis of Pentacarbonyliron in Low Temperature Matrices. Pentacarbonyliron Fe(C0)j provides an adequate system for photochemical studies in low temperature matrices in view of its role in catalytic and photochemical reactions and its simple structure. The formation of Fe(C0)j fragments (n=l-4) was reported based on the IR spectra of the UV photolysis products of matrix-isolated Fe(C0)j (18). We first measured the MBssbauer spectra of unstable species such as Fe(C0)2, Fe(CO)3, Fe(CO)4, Fe2(C0)g arising from the photolysis of Fe(C0)5 isolated in a... 

The removal of halogen with intermolecular formation of a new carbon-carbon double bond may be regarded as an extension of the Wurtz-Fittig reaction it has been applied almost exclusively to the preparation of hydrocarbons but its importance is mainly in the stilbene series. Buckles and Matlack870 prepared tetraphenylethylene in 70% yield by treating diphenylmethylene dibromide with copper powder and tetrakis-(p-nitrophenyl)ethylene has been obtained in 47% yield from bis-(p-nitrophenyl)methylene dibromide by means of pentacarbonyliron.8 71... 

---