Toward iron

The chemistry of l-rerr-butyl-3,4-dimethylphosphole toward iron carbonyls differs in some respects (81IC2848). Thus, with Fc3(CO)l2, complexes containing the... 

Williams, S. M., Ainsworth, R. G., and Elvidge, A. F., A method of assessing the corrosivity of water towards iron , Source document 3, Water Mains Rehabilitation Manual, Water Research Centre/Water Authorities Association (1986)... 

The corrosion of iron (or steel) can be inhibited by the anions of most weak acids under suitable conditions " . However, other anions, particularly those of strong acids, tend to prevent the action of inhibitive anions and stimulate breakdown of the protective oxide film. Examples of such aggressive anions are the halides, sulphate, nitrate, etc. Brasher has shown that, in general, most anions exhibit some inhibitive and some aggressive behaviour towards iron. The balance between the inhibitive and aggressive properties of a specific anion depends on the following main factors (which are themselves interdependent). 

When aluminium is immersed in water, the air-formed oxide film of amorphous 7-alumina initially thickens (at a faster rate than in air) and then an outer layer of crystalline hydrated alumina forms, which eventually tends to stifle the reaction In near-neutral air-saturated solutions, the corrosion of aluminium is generally inhibited by anions which are inhibitive for iron, e.g. chromate, benzoate, phosphate, acetate. Inhibition also occurs in solutions containing sulphate or nitrate ions, which are aggressive towards iron. Aggressive anions for aluminium include the halide ions F ,... 

If this mechanism is correct, the aconitase reaction is an excellent illustration of the influence of the stereochemistry of the metal, as well as its charge, upon the course of a biochemical reaction. The charge on the iron is, of course, responsible for the formation of the resonating carbonium ions A and B from C, D, or E. In C and D the flow of electrons toward iron severs the bond between carbon and the hydroxyl group, whereas in E the proton is released from coordinated water and attached to one of the two ethylenic carbon atoms. The stereochemistry of the iron atom can be credited with holding the organic molecule and the hydroxide in their proper spatial relationship in A and B. It has been recently demonstrated that the complexes of the aconitase substrates with nickel have the structures postulated by Speyer and Dickman and shown in Figure 3 (19). 

Flow of electrons away from the iron will place a positive charge (effective) on Fe. The trans cyanide group in 8 (L = C6H5CH2NC, L" = CN) competes for the same set of orbitals and since it is a strong electron donor toward iron, it renders iron least positive and therefore enhances structure 8. Since the inductive effect is presumably small and since one aromatic ring in II appears more reactive toward N02 than the others, hypothesis 2 is the more probable one. A... 

Compound 59 forms complexes of the type L(CuC1)2, L2CuBr2, L2PdCl2 IR spectra show coordination to be via the nitrogen lone pairs. They show a bridging tendency toward iron and molybdenum in, e.g., LFe2(CO)7 and [LMo(CO)4]2.72... 

If uranium were split into three parts, the segments would be nuclei of smaller atomic numbers, more toward iron on the graph of Figure 4.29. The resulting mass per nucleon would be less, and there would be more mass converted to energy in such a fissioning. 

The tetrathiomolybdate anion [MoS4]2 acts as a chelating ligand toward iron in both diiron complexes [Fe2(SR)2(NO)4] and tetrairon complexes [Fe4S3(NO)7] and [Fe4S4(NO)4] to yield two paramagnetic iron-nitrosyls which have been assigned (55) the constitutions 15 and 16 ... 

Naturally occurring and synthetically accessible siderophores (iron carriers) contain predominantly bidentate pyrocatechinato- or hydroxamato ligands and are of special interest because of their high affinity towards trivalent metal ions, especially towards iron(III) ions [5, 118-127]. The methyl ( )-2-(l-alkyl/aryl-4,5-dihydro-l//-tetrazol-5-ylidene)-2-cyanoacetates 41a-c, first prepared by us [128], also appeared to be suitable as siderophores. 

Whereas the enolates of 41a-c function as bidentate ligands towards iron(III) ions and form the neutral mer-complexes 42a-c, the enolates of the same compounds 41a-c should function as tridentate ligands towards iron(II) ions and afford, by spontaneous self-organization [102,103,132], neutral three-dimensional coordination polymers [132-153],... 

Pyridine /V-oxide is unreactive toward iron-catalyzed bromination at 110°C (55JA2902), but silver sulfate-catalyzed bromination in sulfuric acid at 200°C gives a 10% yield of 2- and 4-bromination in the ratio 1 2 (6ITL32). With bromine in oleum the main product is 3-bromopyridine /V-oxide (60%) together with the 2,5-dibromo (—35%), and 2,3- and 3,4-dibromo compounds (—5%) (62T227). Presumably the N-oxide function is here complexed with sulfur trioxide, which causes deactivation and 3-orientation. Bromination in acetic anhydride also gives 3-substitution (35%) an addition-elimination mechanism has been proposed (65JPJ62). 

The water i beautifully softened, but is rendered more corrosive towards iron and steel. 

The two sites also differ in their pH stability towards iron release. Experiments on serum transferrin showed that one site loses iron at a pH near 6.0, and the other at a pH nearer 5.0 (203, 204), giving a distinctly biphasic pH-induced release profile (Fig. 28). The acid-stable A site was later shown to be the C-terminal site (202). It is this differential response to pH, together with kinetic effects (below), that enables N-terminal and C-terminal monoferric transferrins to be prepared (200). Although the N-terminal site is more labile, both kinetically and to acid, the reasons are not necessarily the same the acid stability may depend on the protonation of specific residues (Section V.B) and is likely to differ somewhat from one transferrin to another in response to sequence changes. The biphasic acid-induced release of iron seen for transferrin is not shared by lactoferrin. Although biphasic release from lactoferrin, in the presence at EDTA, has been reported (205), under most conditions both sites release iron essentially together at a pH(2.5-4.0) several units lower than that for transferrin (Fig. 28). 

The revised version of the crystallographic FeMo-co model implies an obvious reappraisal of the synthetic structural modeling toward iron-sulfur nitride chemistry, a held that does not currently exist as such." ... 

Reactions of anionic metal complexes with halide-bridged dimers can also be used to form a bond between two different metal atoms. Reaetion of (/j -C7H7)Fe(CO)3 with Mn2(CO)gBr2 gives ()j -C7H7)MnFe(CO)6 in which the cycloheptatrienyl ligand coordinates as a diolefin to manganese and as an allyl toward iron . 

A class of tripodal ligands such as (131), synthesized by reaction of 3,5-dimethylaniline and nitrilotriacetic acid with triphenylphosphite, has been reported and its coordination chemistry toward iron nitrosyl acceptors has been investigated. When bonded to a metal ion, they form cavities around vacant coordination sites on metal ions.210... 

Neocuproine is as specific for copper(l) as cuproine is. Substitution of methyl groups at the 2- and 9-positions in 1,10-phenanthroline renders the reagent unreactive towards iron(Il). 

Polystyrene-divinylbenzene polymer matrices, with a thiourea functional group, show good selectivity towards iron and copper, and effectively bind and remove them, both in batch and column operations. The adsorption mechanism can be explained by the coordination between ligand and metal ions [12]. 

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