Substituted iron carbonyls

Studies have also been made of cyclo-octatetraene derivatives of the type (COT)Fe(CO)3 and (COT)[Fe(CO)3]2 [14], and solid and frozen solution data show that there is no appreciable change in the conformations of the molecules between the two phases [15]. 

6-coordination of the iron (Table 9.3). This is particularly emphasised by the large quadrupole splitting of 2-58 mm s for (OC)4Fe(PMe2)2Fe(CO)4 which is 5-coordinate and the small value of 0-99 mm s for the complex I(OC)3Fe(PMe2)2Fe(CO)3l which is already 6-coordinate without the iron-iron bond (structures 17-18). 

The overall impression is one of insensitivity to substitution in general, but strong dependence on stereochemistry. Substitution of a terminal carbonyl 

Mossbauer datahaveprovided useful evidence in the assignment of possible structures for new complexes, and have shown both environments to be equi- 

The binuclear compounds of which ffarsFe2(CO)6 is an example are believed to have structure 24. The two iron atoms are not identical, although that bonding to the butene ring (atom B) is expected to be less sensitive to 

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A98. N. N. Greenwood and T. C. Gibb, Mossbauer Spectroscopy. Chapman Hall, London, 1971. Chapter 9, pp. 221-238 Covalent iron compounds (41), treats binary carbonyls, carbonyl anions, hydride anions, substituted iron carbonyls, ferrocene and other 7r-cyclopentadienyl iron derivatives. 

Substitution of carbon monoxide ligands by one acetylene is the first step in the reaction of alkynes with metal carbonyk. This is well-established in the case of cobalt carbonyls by the isolation of substitution-type complexes of formula RC R Co CCO) (1) and RC2R Co (CO)j (2). Three different types of alkyne-substituted iron carbonyls have been isolated from iron carbonyls particularly with acetylenes having bulky substituents (3). They have recently been shown to be intermediates in the formation of complexes with more complicated organic ligands as well as of cyclic organic products. 

B3 ALKYNE-SUBSTITUTED IRON CARBONYLS OF FORMULA RCjR Fejj(CO)y, C. Hoogzand and W. HUbel... 

The substituted iron carbonyls Fe(CO)4PPh3 and Fe(CO)3(PPh3)2 have also been examined as photocatalysts for hydrosilation however, the qualitative reactivity features were found to be similar to those of Fe(CO)s [74]. In addition the polymer anchored derivatives Fe(CO)4(PPh2-poly) and Fe(CO)3(PPh2-poly)2 (where PPh2-poly is the polystyrene bound diphenyl phosphine) proved to be effective photocatalysts for lx)th hydrosilation and hydrogenation [74]. Photocatalysis of alkene hydrosilation is also effected by metal carbonyl clusters [61]. 

A nitrogen-substituted iron carbonyl-cyanide complex 24 has been prepared from (Me3TACN)FeCl2 by adding cyanide ions in the presence of GO (Me3TAGN =iV,iV, A -trimethyl-l,4,7-triazacyclononane). ... 

The photolytic production of substituted iron carbonyls in neat PEts has been examined (Scheme 36). " The product is a mixture of Fe(CO)4(PEt3> and Fe(CO)3(PEt3)2. Triplet state Fe(CO)3PEt3 was determined to be an intermediate based upon the spectroscopic data. 

Substituted iron carbonyl complexes ineluding Fe(C0)3 As(C6H40Me-/>)3)2 and Fe(C0)4 As(C6H40Me-/>)3) were examined by electrospray mass spectrometry (ESMS). Whereas the related compound Fe(CO>3(AsPh3)2 did not give an ESMS spectrum, the methoxy-substituted compounds did. This was attributed to the presence of protonatable methoxy groups. Both the monosubstituted and disubstituted compounds were observed in a crude... 

In addition to benzene and naphthalene derivatives, heteroaromatic compounds such as ferrocene[232, furan, thiophene, selenophene[233,234], and cyclobutadiene iron carbonyl complexpSS] react with alkenes to give vinyl heterocydes. The ease of the reaction of styrene with sub.stituted benzenes to give stilbene derivatives 260 increases in the order benzene < naphthalene < ferrocene < furan. The effect of substituents in this reaction is similar to that in the electrophilic aromatic substitution reactions[236]. 

Reactions of acetylene and iron carbonyls can yield benzene derivatives, quinones, cyclopentadienes, and a variety of heterocycHc compounds. The cyclization reaction is useful for preparing substituted benzenes. The reaction of / fZ-butylacetylene in the presence of Co2(CO)g as the catalyst yields l,2,4-tri-/ f2 butylbenzene (142). The reaction of Fe(CO) and diphenylacetylene yields no less than seven different species. A cyclobutadiene derivative [31811 -56-0] is the most important (143—145). 

Pyridazines form complexes with iodine, iodine monochloride, bromine, nickel(II) ethyl xanthate, iron carbonyls, iron carbonyl and triphenylphosphine, boron trihalides, silver salts, mercury(I) salts, iridium and ruthenium salts, chromium carbonyl and transition metals, and pentammine complexes of osmium(II) and osmium(III) (79ACS(A)125). Pyridazine N- oxide and its methyl and phenyl substituted derivatives form copper complexes (78TL1979). 

Direct substitution of the carbonyls themselves is of course possible. Besides Group 15 donor ligands, unsaturated hydrocarbons give especially interesting products. The iron carbonyl acetylenes provided early examples of the use of carbonyls in organic synthesis. From them a wide variety... 

Hydroxy-substituted iron-acyl complexes 1, which are derived from aldol reactions of iron-acyl enolates with carbonyl compounds, are readily converted to the corresponding /i-methoxy or /1-acetoxy complexes 2 on deprotonation and reaction of the resulting alkoxide with iodomethane or acetic anhydride (Tabic 1). Further exposure of these materials to base promotes elimination of methoxide or acetate to provide the a,/ -unsaturated complexes (E)-3 and (Z)-3 (Table 2). 

Syntheses of primary ally lie amines have been reviewed183. The regiochemistry of the reaction of iron carbonyl complexes with nucleophiles such as morpholine has been investigated. The (r 3-crolyl) Fe+(CO)4 BF4- complexes 172 (R1 = H R2 = Me or R1 = Me R2 = H) undergo preferential attack at the less substituted allyl terminus to yield allylic amines 173. The (/j2-crotyl acetate) Fe(CO)4 complex 174, on the other hand, does not react with morpholine184. 

A diene system with unsymmetrical 1,4-disubstitution is converted to the iron carbonyl complex 1 which is resolved into its enantiomers. The aldehyde function is conformationally locked in the transoid position and is diastereofacially shielded from the bottom face. Nucleophiles attack from the top face with high selectivity. Alternatively, chain elongation leads to the triene 2 which is reacted with diazomethane. Cerium(IV) oxidation removes the metal and furnishes the substituted cyclopropane 3. 

Substituted cyclopentadienones react with iron carbonyls to form stable, diamagnetic 7r-co triplexes of the type [Fe(CO)3(cyclopentadienone)] (215). The proposed structure is shown in (XX). These complexes undergo reactions typical of metal carbonyls, e.g., displacement of carbon monoxide by tertiary phosphines, but the carbonyl group of the ligand does not show reactions characteristic of a keto-group. These complexes are also formed by interaction of acetylenes with iron carbonyls (see Section VI,C). Interaction of tetracyclone and Fe3(CO)i2 gives unstable complexes which contain the sandwich anion [Fe(tetracyclone)2]2 analogous to the anion (XXV) (215). 

Among the sulfur-bridged trinuclear iron carbonyls S2Fe3(CO)g (structure like [25]) has been prepared in a new way (52), and CO substitutions of this (52) and the... 

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