Iron complex directly bonded

Mossbauer spectra of FePc on carbon supports after thermal treatment and have concluded that high activity is exhibited only by those FePc complexes in which the iron is directly bonded to the carbon substrate through an Fe-C bond. It is not completely clear, however, what spin state to expect for such Fe species. Melendres " has also compared the Mossbauer and Raman spectra of carbon-supported FePc and the pure complex and finds evidence of catalyst-support interactions with the former. 

Unexpectedly, neither direct complexation nor the deoxygenated complexes 95 or 96136,137 were observed in the reaction of diphenylthiirene oxide (18a) with iron nonacarbonyl. Instead, the red organosulfur-iron complex 97138 was isolated12, which required the cleavage of three carbon-sulfur bonds in the thiirene oxide system (see equation 33). The mechanism of the formation of 97 from 18a is as yet a matter of speculation. 

The first report on an iron complexed phosphinidene appeared in 1984 by Bertrand and coworkers [63]. They reported that abstraction of Cl" from 22 with PhjC+PFg at -90 °C presumably results in cationic phosphinidene complex 23, which was based on its downfield P NMR resonance at 954 ppm. Above -68 °C the phosphorus center inserts into a isopropyl C-H bond to give 24 as only isolable product. Dehalogenation with AICI3 resulted directly in the AICI4 salt of 24. 

Recently, molecular orbital calculations on some iron complexes have been made by Gray and his co-workers (2, 30). These values for ferrous complexes are plotted in Figure 2 as the dashed line [3d 4s (MO)]. Hence, Mossbauer spectroscopy provides estimates for the 4s electron contribution for molecular orbital calculations. This correlation does not hold for high spin complexes such as FeCb" and FeFe ". Bersuker (3, 4) has attempted to relate both S and AEq directly to molecular orbital parameters. Using the equations developed from this approach, Bersuker, Gordanskii, and Makarov (5) have concluded that in tin tetrahalides the role of dx-Px bonding is significant. 

Reaction of the iron complex salt 602 with the arylamine 921 in the presence of air led directly to the tricarbonyl(ri -4b,8a-dihydro-9H-carbazole)iron complex (923) by a one-pot C-C and C-N bond formation. Demetalation of complex 923 and subsequent aromatization by catalytic dehydrogenation afforded 3,4-dimethoxy-l-heptyl-2-methylcarbazole (924), a protected carbazoquinocin C. Finally, ether cleavage of 924 with boron tribromide followed by oxidation in air provided carbazoquinocin C (274) (640) (Scheme 5.120). 

At the same time the bond angles (C—N—C) at the N7 position vary from 112 (-fp3 as expected for an amine ligand) in the manganese complex (where repulsion is least) up to a maximum value of 120 in the iron complex with maximum repulsions. The tertiary amine nitrogen atom (N7) corresponds to a three-ribbed umbrella that has been inverted by the wind (the handle is the lone pair directed at the metal). As the a, and If levels fill, the repulsions increase, the metal-nitrogen distance increases, and the umbrella begins to flatten ... 

The rate of the spin state change for the octahedral cobalt(II) complexes is expected to be faster than that observed for the iron(II) and iron(III) complexes. In the cobalt(II) case the spin state change involves only one electron, that is AS = 1. The 2E and 4T states are directly mixed by spin-orbit coupling (10, 163). The spin state transition should be adiabatic, with k = 1, without any spin-forbidden barrier. Furthermore, the coordination sphere reorganization involves a change in bond length of 21 pm along only two bonds, instead of all six bonds as in iron complexes. Both of these factors lead to the prediction of rapid spin state interconversion. 

Mercaptoethanol (0.42 M) destroyed the chromogenic capacity of metal-free ovotransferrin with little or no effect on the iron complex. 2-Mercaptoethanol was effective on the metal-free ovotransferrin at a lower concentration in the presence of urea. Similar effects were obtained with sulfite and urea, and the inactivations obtained were directly proportional to the number of disulfide bonds cleaved (Table 12). When slightly under half of the disulfide bonds were cleaved (4.8 or 11 total), essentially complete and irreversible inactivation of metal-free ovotransferrin... 

A few dinuclear complexes are known, in which the a-CH bond of a metal-bonded alkyl group is tj2 coordinated to another metal moiety, similar to the previously discussed dinuclear silyl complexes. In the iron complex 22 (75) both metal moieties are the same, and therefore the Fe—C distances [202.5(3) and 211.3(3) pm] can be directly compared without correction. The relative lengthening of the M—C distance of the Fe—H—C three-center bond (4.5%) is comparable to that in the silane-bridged titanium complex 13 (6.5%), corresponding to a similar stage of the oxidative addition. 

The structure of the di-iron complex [Fe2( i, r 3, r 3-BH6)(PEt3)6] (127) contains a boron atom in the octahedral environment of 6 equiv. hydrides capped on the opposite facets by two iron atoms.199 Thus, neglecting the second iron center, the geometry is very reminiscent of the complex 125. DFT calculations supplemented by an AIM study confirmed the presence of six H-B interactions and direct Fe B bonds. The structure was considered as containing a boron trication B3+ sandwiched between two anions [Fe(H)3(PEt3)3]. ... 

In practice, for all known >7 complexes the d orbital may be considered as donating two electrons to the M-O2 bond. For the well characterised complexes of iron and cobalt the d orbital contributes respectively 0 and 1 electrons to the bond. It has been suggested that the heats of oxygenation of cobalt complexes are slightly less negative than those of the equivalent iron complexes as a result of the partial occupation of the d - r (i) antibonding orbitaF but it is not certain that the data available may be compared directly There is some evidence that addition of one electron to an cobalt complex... 

It is difficult to find direct bonding interaction between the ferrocene iron and the second transition metal in the hetero-bimetallic complexes. Only the mono-triphenylphosphine palladium and platinum compounds fc[E2M(PPh3)] (E = O, M = Pd (Scheme 5-14) [79] E = S, M = Pd [268, 269], and Pt [269]) appear to... 

Reaction of NaBH4 with the iron complex 486 (L = phosphine ligand) leads to C—C and Fe—Fe bond formation to give compound 487. Oxidative cleavage of the intermetallic bond produces a complex (488) containing a tetrathiooxalate ligand. Sodium amalgam yields 488 directly. When L... 

Iron complex (49) adds C02 by direct insertion into the Fe—C bond in THF at room temperature (Equation (5)) <77CB2213>. Lower temperature and a nonpolar solvent decrease the concentration of the metallacycle and the reaction leads to other products. The iron compound also adds to 1,3-cyclohexadiene <87JCS(D)203i>. 

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