Iron complex, spectrum

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... 

Fink and Babik reported that propylene polymerization was achieved by a bis (imino)pyridine iron complex with Ph3C[B(C6p5)]4] and ttialkylaluminium as additives [127]. Both 3-methyl-"butyl and "butyl endgroups were observed by NMR spectrum when ttiisobutylaluminium as an activator was used, whereas the only "propyl endgroup was formed in case of triethylaluminium activation. In addition, this polymerization proceeds two times faster with than without a hydrogen atmosphere, but the value decreases and the M IM value rises up. 

Chemically the iron complex 18 is reduced by K/Na alloy in THF to give a green solution of the salt 57. The d7 anion in 57 has been characterized by its ESR spectrum in frozen solution (62). Similarly, on treatment with sodium amalgam, the cobalt complexes 7 and 13 yield dark brownish-red solutions of 58 and 59, respectively. A surprisingly robust PPh4+ salt 60 (mp 158-159°C) could be isolated. Solution and solid state magnetic measurements confirm the presence of two unpaired electrons in these 20-e species as in NiCp2 (60). 

The pentanuclear carbido species Ms(CO)lsC (M = Fe, Ru, Os) have been prepared. The iron compound has been known for some considerable time (209), but the ruthenium and osmium complexes were prepared recently by pyrolysis reactions (210). The ruthenium adduct was only isolated in low yield (—1%), while the osmium complex was obtained in higher yield (—40%). The infrared spectrum and mass spectral breakdown pattern indicate a common structure to these compounds. The molecular structure of the iron complex is shown in Fig. 46. 

The stepwise oxidation of alkylamine, which leads to N-dealkylation, generates nitrones that form tightly bound complexes with the heme iron [48]. These heme iron complexes give rise to characteristic changes in the UV-Vis spectrum of the CYP. 

As one may expect from the diversity of microorganisms that can reduce iron, the spectrum ranges from bacteria that can use only amorphous Fe(III) hydroxide/oxide (e.g., T. ferrireducens) and apparently require direct contact with the Fe(III) precipitate, as shown by electron micrographs (Slobodkin et al. 1997b), to bacteria that can utilize various forms of Fe(III) ion as precipitated hydroxide or as complexed soluble ions, such as Fe(III) citrate, to bacteria such as T. saccharolyticum that can use only soluble Fe(III) citrate but are stimulated by the addition of increased Fe(III) ions. Further studies must to be done to elucidate the nature and which of the bacteria excrete electron mediators (so no direct contact would be required) and which contain cell-wall-bound reductases (which require a direct contact with the Fe(III) precipitate). 

The compound cyclopentadienylcyclo-octatetraenecobalt is probably analogous to the compound cyclopentadienyl cyclopentadienecobalt (XXIV). The cyclo-octatetraene residue shows two proton resonance lines in the nmr spectrum (167) in contrast to that in the iron complex [Fe(CO)3(cyclo-octatetraene)] which shows only one proton resonance line (152, 180). 

Mossbauer spectroscopy of the 57Fe nucleus has been extensively used to investigate aspects of spin equilibria in the solid state and in frozen solutions. A rigid medium is of course required in order to achieve the Mossbauer effect. The dynamics of spin equilibria can be investigated by the Mossbauer experiment because the lifetime of the excited state of the 57Fe nucleus which is involved in the emission and absorption of the y radiation is 1 x 10 7 second. This is just of the order of the lifetimes of the spin states of iron complexes involved in spin equilibria. Furthermore, the Mossbauer spectra of high-spin and low-spin complexes are characterized by different isomer shifts and quad-rupole coupling constants. Consequently, the Mossbauer spectrum can be used to classify the dynamic properties of a spin-equilibrium iron complex. 

Isolation of 3-cyclopropenyl metal compounds by this method has been achieved so far for iron and rhenium metals only. Thus, the reaction of Na[CpFe(CO)J (NaFp) with cyclopropenylium salts at -70 °C, in THF, gave 3-Fp-cyclopropene complexes (equation 194)2 267. The X-ray crystal structure of the most stable iron complex 3-Fp-C3Ph3 exhibits a regular cyclopropene C—C single and double bond distances (151 and 129 pm), and a characteristic distance of 208 pm for the Fe—C (T-bond267. The H NMR (CS2) spectrum of the 3-Fp-C3Ph,H complex displays a singlet at S = 2.63 ppm, of the cyclopropen yl proton at the 3-position. ... 

The NMR data for compounds (47) and (48) are given in Table I. A similar NMR spectrum has been reported by Ariyaratne and Green for the ir-vinyl iron complex (39) (40). 

The use of pyridine as solvent dramatically alters the spectral properties of the iron complex of octamethylcorrole. Such a spectrum is reported in Fig. 20 and pertinent data in Table 12. The three resonances (A-C) observed at low field have been attributed to the methyl substituents, the fourth resonance probably being located in the diamagnetic region obscured by the solvent resonances. 

Fig. 17. Spectral shifts of iron complexes caused by succinylating ovotransferrin to varying degrees. The protein was succinylated in the iron-free state. Following dialysis and lyophilization, the modified transferrins were redissolved and saturated with iron, and the visible spectrum was scanned with a Beckman DB recording spectrophotometer. ------, original ovotransferrin (Xmax 465 mg) ---------, succiny-...

Electron paramagnetic resonance (EPR) spectroscopy is a powerful technique to explore the electronic state of iron complexes. EPR spectroscopy of the non-heme iron component in the electron transfer system of mitochondria has been extensively used and discussed by Beinert (9), who showed that this type of iron has a so-called g = 1.94 type signal upon reduction. Consideration of the EPR spectrum of adrenodoxin has been described previously (68). 

Azepine derivatives form a diene complex with (tricarbonyl)iron, leaving the third of the double bonds uncomplexed. If the 3-position is substituted, two different such complexes are possible and are in equilibrium, as seen in the 11 NMR spectrum. An ester group in the 1-position of the complex can be removed by hydrolysis to give an NH compound that, in contrast to the free 1 //-azcpinc, is stable (Scheme 82). The 1-position can then be derivatized in the manner usual for amines. The same (tricarbonyl)iron complex can, by virtue of the uncomplexed 2,3-double bond, serve as a dienophile with 1,2,4,5-tetrazines. The uncomplexed N-ethoxycarbonylazepine also adds the tetrazine, but to the 5,6-double bond. Thus, two isomeric adducts can be synthesized by using or not using the complex (Scheme 83). 

Two doublets and one pseudotriplet, observed in the H nmr spectrum for the PCH3 groups,16 are characteristic for two chemically different methylphos-phine ligands that are linked to the metal in cis position and two methylphos-phine ligands that are linked in tmns positions.20 The structure shown in Fig. 2 best fits these findings. The X-ray structure of a closely related CS2 iron complex has been determined.21... 

Given the similarities in chemical shifts and linewidths, as well as the contributions of symmetry to the appearance of the spectrum, the electronic and molecular structure of new iron complexes of N-alkyl-porphyrins may be ascertained, to a first approximation, from NMR data. Thus for low-spin iron(III) complexes one would expect at least four sharp resonances upfield of the diamagnetic region. Iron(IV) complexes should have at least four resonances upfield of the diamagnetic region. Iron(III) can be differentiated from iron(IV) by measurement of the solution susceptibility (51). 

Figure 3,5-16 Spectrum of an organic iron complex, 100 scans, 8 cm, a exciting radiation 100 mW, unfocused b 180 mW, unfocused c 45 mW, focused, for b and c the intensity of the range above 2200 cm is reduced to 1/3 (Sawatzki, unpublished).

Some analogous rathenium- and osmium-bismuth clusters have been found. Examples include Bi2M3(CO)9 and H3BiM3(CO)9 (M = Ru, Os). The stmctures of the hydride compounds have both been determined and they are isostractural with the iron complexes as is Bi2Ru3(CO)9 withBi2Fe3(CO)9. The structure 0fBi2Os3(CO)9, on the other hand, has not been determined and its IR spectrum indicates that it probably has a different structure. A spirocyclic cluster [Ru2(CO)8(/X4-Bi)Ru3(CO)io(/x-Ft)] (39) has been reported. 

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