Iron Pentacarbonyl Ions

If the radical is square pyramidal (C4 ) Fe(CO)5+ (1), the principal axes of the g-matrix must be the molecular axes (the C4 axis and normals to the reflection planes). The iron atom and the carbon of the axial CO group would have the full symmetry of the group and so these hyperfine matrices would share principal axes with the g-matrix. The four equatorial carbonyl carbons, on the other hand, lie in reflection planes, but not on the C4-axis and so are symmetry-required to share only one principal axis with the g-matrix. In fact, the major matrix axes for the equatorial carbons are tilted slightly in the -z direction from the ideal locations along the x and y axes. The g-matrix suggests that the metal contribution is dz2 and the iron hyperfine matrix then can be used to estimate about 55% iron 3d and 34% axial carbon 2pz spin density. The spin density on the equatorial carbons then is mostly negative and due to spin polarization. 

The other species observed in irradiated Fe(CO)5-doped crystals of Cr(CO)6 also showed coupling to 57Fe, to a unique 13C, and to four other carbons. However, in this case g, AFe, and AC1 have only one matrix axis in common (that corresponding to the third component of each matrix listed in Table 4.10). 

Coupling constants in units of 10 4 cm. Data from refs. 40 and 41. 

The most striking feature of these results is the orientation of the unique 13C hyperfine matrix axes, relative to those of the 57Fe hyperfine axes. This orientation led Fairhurst et al.41 to assign the spectrum to [Fe(CO)5] (2) and to describe the species as a substituted acyl radical. However, these authors did not discuss the orientation of the g-matrix axes. The y-axis, normal to the reflection plane, is common to all three matrices. The x- and z-axes of the g-matrix, however, are oriented about 21° away from the corresponding 57Fe hyperfine matrix axes. Since the iron d-orbital contribution to the SOMO appears to be nearly pure dz2, the 57Fe hyperfine matrix major axis must correspond to the local z-axis, assumed to be essentially the Fe-C bond. Thus we must ask Why are the g-matrix axes different The SOMO can be written  

Assuming that there is only one n orbital close enough in energy to couple significantly, eqn (4.11) gives the g-matrix components  

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The preparation of film electrodes Prussian blue films are usually prepared by cycling an electrode in a freshly prepared solution containing iron(III) and hexacyanoferrate(III) ions [70-72]. As substrate, mostly platinum is used, sometimes glassy carbon [73] is used, and very frequently ITO electrodes [74] are used because the latter are very useful for electrochromism studies. Similar procedures using solutions containing metal ions and hexacyanoferrate(III) have been used to deposit cobalt hexacyanoferrate [75] and chromium hexacyanoferrate [76, 77]. Crumbliss et al. reported a plasma deposition of iron species from a plasma containing iron pentacarbonyl and ethane, followed by electrochemical derivatization of the deposited iron sites with the help of hexacyanoferrate solutions [78]. 

Ion-exchange resins 55, 3 Iron, tricarbonyldiene complex, 57, 16 Iron pentacarbonyl, 57, 108,58, 61 Isobutyl fluoride, 57, 73 3-ISOCHROMANONE.6.7-D1METHOXY-, 55,45... 

Several preparations of dicarbonyl dinitrosyl iron have been reported including treatment of [Fe3(CO)i2] or [Fe2(CO)9] with nitric oxide,86,87 acidification of a mixture of [HFe(CO)4]- and nitrite ion,88 reaction of iron pentacarbonyl with nitrosyl chloride89 and acidification of a mixture of [Fe(CO)3NO]- and nitrite ion90 as in equations (2) and (3). 

Dienes are generally much less reactive when coordinated to transition metals than when in an uncoordinated state. An important discovery was thus made by Fischer and Fischer (86) in 1960 when they found that cyclo-hexadiene-iron tricarbonyl (XV) (formed from 1,3-cyclohexadiene and iron pentacarbonyl) undergoes hydride ion abstraction by triphenylmethyl tetrafluoroborate to form 7r-cyclohexadienyl-iron tricarbonyl tetra-fluoroborate (XVI) ... 

Among the complexes which may function in this way are pentacyano-cobaltate ion, iron pentacarbonyl, the platinum-tin complex, and iridium and rhodium carbonyl phosphines. It has been suggested that with tristriphenylphosphine Rh(I) chloride, a dihydride is formed and that concerted addition of the two hydrogen atoms to the coordinated olefin occurs (16). There are few examples of the homogeneous reduction of other functional groups besides C=C, C=C, and C=C—C=C penta-cyanocobaltate incidentally is specific in reducing diolefins to monoolefins. 

The gas-phase reactions of lanthanide (Ln+ = La+-Lu+, except Pm+) cations with iron pentacarbonyl, Fe(CO)s, and with ferrocene, Cp2Fe, have been studied by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/ MS). In the case of Fe(GO)s, the observed primary products were of the type LnFe(CO)x+ (Ln = La, Ce, Pr, Nd, Gd, Tb v = 3 Ln = Ho, Er, Lu x = 3 and 4 Ln = Sm, Eu, Dy, Tm, Yb x = 4), and evidence was obtained for the presence of direct Ln-Fe bonds in these species. With Cp2Fe the majority of the Ln+ cations reacted by metal exchange, yielding Ln bis(cyclopentadienyl) ions Cp2Ln+, while the less reactive Ln+ cations formed the adduct ions LnFeCp2+.851... 

From Fig. G.l we find that an iron atom in the elemental state has 8 valence electrons. We arrive at the oxidation state of iron in iron pentacarbonyl by noting that the charge on the complex as a whole is zero (it is not an ion), and that the charge on each CO ligand is also zero. Therefore, the iron is in the zero oxidation state. 

This is the earliest method used for the preparation of alkali metal and other derivatives of metal carbonyl anions. In 1931 the reaction between iron pentacarbonyl and aqueous hydroxide ion to give the [Fe(CO)4] " anion was first described (2). Since that time the reactions between hydroxide ion and various metal carbonyl derivatives have been used to prepare a variety of anions, as illustrated by the following equations. 

The only known example is the reaction between iron pentacarbonyl and potassium nitrite, preferably in the presence of a base producing the [Fe(CO)3NO]- ion (5, 80, 81)... 

Treatment of iron pentacarbonyl with nitrite ion at 25-40° C in methanol solution 81)... 

Butanol is prepared commercially by the iron carbonyl-promoted hydro-xymethylation of propylene (Reppe and Vetter, 1953). Iron pentacarbonyl and a tertiary amine serve as a good catalyst system. The active species has been shown to be HFe(CO)4 formed from the metal carbonyl and hydroxide ion (Wada and Matsuda, 1974). 

A crucial concept in the definition of stereoisomers given above is "connectivity". In methane or 2,3-dichlorobutane, there is no doubt as to the connectivity of the system. However, there is an innate arbitrariness to the term, and this can lead to some ambiguity about stereoisomerism. For example, do hydrogen bonds count in our list of connectivity No, but consider the implications of this. If hydrogen bonds "don t count", then how do we think about isomerism in double-helical DN A Do we just ignore the interaction of the two strands As a simpler comfortable with a clear connectivity pattern in inorganic complexes such as iron pentacarbonyl or a porphyrin complex. But what about Mg ions complexing a carbonyl When is a bond too weak to be considered relevant for stereoisomerism . Mg" Mgr O 0 V ... 

It consists of Pt with two NH3 molecules (neutral) and two CP ions, giving a neutral species. Iron pentacarbonyl, Fe(CO)5, is an example of a neutral species formed from a neutral iron atom and CO molecules. 

A deformation of the bonds of the digonal carbon atom, analogous to V and XVIII, has also been found in the reaction of nucleophilic addition of a hydride-ion to iron pentacarbonyl which gives the formyl complex XXI ... 

The reaction of sodium hydroxide with iron pentacarbonyl results in a nucleophilic attack by a hydroxide ion on the carbonyl group to give a metal carboxyHc add complex. Upon further action with sodium hydroxide, the carboxyHc add gives up carbon dioxide to form a hydrido anion. The protonation of this anion results in the formation of iron tet-racarbonyl hydride (Fleiber base) as... 

The mass spectra of binuclear iron carbonyl complexes of acenaphthylene and azulene have been briefly reported 26). The acenaphthylene complex previously 43> reported as Ci2H8Fe2(CO)6 exhibits Ci2H8Fe2 (CO)5 as the highest m/e ion the implied pentacarbonyl formulation was later 44> confirmed by X-ray crystallography which indicated structure 16. The reaction between azulene and Fe(CO)s has been reported 45> to give dark red CioHgFegfCOJs this formulation was confirmed by... 

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