Iron ll

Convert iron(ll) to iron(lll) in aqueous acid solution. 

The reduction of a nitrate, for example potassium nitrate, by iron(ll) sulphate in the presence of concentrated sulphuric acid gives reasonably pure nitrogen monoxide. The mixture is warmed and at this temperature the nitrogen monoxide produced does not combine with uncharged iron(II) sulphate (see below). 

Many of these sulphides occur naturally, for example iron(ll) sulphide, FeS (magnetic pyrites), and antimony(III) sulphide, Sb S, (stibnite). They can usually be prepared by the direct combination of the elements, effected by heating, but this rarely produces a pure stoichiometric compound and the product often contains a slight excess of the metal, or of sulphur. 

In what ways do the chemical and physical properties of zinc(ll) differ from those of iron(ll) Account for these differences. Explain what happens when... 

Titrate the permanganate formed with iron(ll) as under iron(ll) Mn/5 = 10.9876... 

The destiny of most biological material produced in lakes is the permanent sediment. The question is how often its components can be re-used in new biomass formation before it becomes eventually buried in the deep sediments. Interestingly, much of the flux of phosphorus is held in iron(lll) hydroxide matrices and its re-use depends upon reduction of the metal to the iron(ll) form. The released phosphate is indeed biologically available to the organisms which make contact with it, so the significance attributed to solution events is understandable. It is not clear, however, just how well this phosphorus is used, for it generally remains isolated from the production sites in surface waters. Moreover, subsequent oxidation of the iron causes re-precipitation of the iron(lll) hydroxide floes, simultaneously scavenging much of the free phosphate. Curiously, deep lakes show almost no tendency to recycle phosphorus, whereas shallow... 

Eisenoxydul, n. ferrous oxide, iron(ll) oxide. — salpetersaures —, ferrous nitrate, iron(ll) nitrate (and so for other salts). 

Eisenoxydul-hydrat, n. ferrous hydroxide, iron(ll) hydroxide, -oxyd, n. ferrosoferric oxide, iron(II,III) oxide, magnetic iron oxide (FeaOi). -salz, n. ferrous salt, iron(II) salt, -sulfat, n. ferrous sulfate, iron(II) sulfate, -verbindung, /. ferrous compound, iron(ll) compound. 

Transition metal ions. Transition metal ions impart color to many of their compounds and solutions, (a) Bottom row (left to right) iron(lll) chloride. copper ll) sulfate, manganese(ll) chloride, cobalt(ll) chloride. Top row (left to right) chromium(lll) nitrate, iron(ll) sulfate, nickel(ll) sulfate, potassium dichromate, (b) Solutions of the compounds in (a) in the order listed above. 

Iron(ll) 2,11,20,29-Tetra(to7-buty I)-1,2-naphthalocyanine "typical Procedure 7 1... 

Induced chain reactions. In acidic solution, oxalic acid reacts very slowly with chlorine, but iron(ll) reacts rapidly." The net reactions are these ... 

FIGURE A.2 Mass is an extensive property, but temperature is intensive. These two samples of iron(ll) sulfate solution were taken from the same well-mixed supply they have different masses but the same temperature. 

FIGURE E.5 Each sample contains 1 mol of formula units of an ionic compound. From left to right are 58 g of sodium chloride (NaCl), 100 g of calcium carbonate (CaCO,), 278 g of iron(ll) sulfate heptahydrate (FeS04-7H.0), and 78 g of sodium peroxide (Na. O,). 

The stoichiometric point is reached when all the Fe2+ has reacted and is detected when the purple color of the permanganate ion persists. A sample of ore of mass 0.202 g was dissolved in hydrochloric acid, and the resulting solution needed 16.7 mL of 0.0108 M KMn04(aq) to reach the stoichiometric point, (a) What mass of iron(ll) ions is present (b) What is the mass percentage of iron in the ore sample ... 

Molecular oxygen is transported throughout the body by attaching to the iron(ll) atom in the heme group of hemoglobin. The iron(ll) atom lies at the center of a square planar complex formed by nitrogen atoms. When the O, molecule attaches to the iron, the plane of the heme group becomes distorted. 

FIGURE 16.16 When potassium cyanide is added to a solution of iron(ll) sulfate, the cyanide ions replace the H.O ligands of the [Fe(H20), - + complex (left and produce a new complex, the hexacyanoferrate(ll) ion, Fe(CN)(l 4 (right). The blue color is due to the polymeric compound called Prussian blue, which forms from the cyanoferrate ion. 

By considering electron configurations, suggest a reason why iron(III) is readily prepared from iron(ll) but the conversion of nickel(II) and cobalt(II) into nickel(III) and cobalt(III), respectively, is much more difficult. 

From 2,6-diacetylpyridine dioxime, ferric chloride hydrate, and phenylboronic acid as starting materials the macrocyclic dinuclear iron(ll) complexes 133 can be prepared (Fig. 36). 

Compounds 139 are tris(oximehydrazone) derivatives with an iron(ll) ion in the center of the cavity [230]. Compound 140 (Fig. 38) has been known for 30 years [231, 232] and was prepared from a tris(2-aldoximo-6-pyridyl)phos-phine that is capped by a BF unit to encapsulate cobalt(ll), zinc(ll), nickel(ll), and iron(II). All four macrocyclic complexes were characterized later by a comparative X-ray crystallographic study [233-236]. 

One-electron oxidation of the vinylidene complex transforms it from an Fe=C axially symmetric Fe(ll) carbene to an Fe(lll) complex where the vinylidene carbon bridges between iron and a pyrrole nitrogen. Cobalt and nickel porphyrin carbene complexes adopt this latter structure, with the carbene fragment formally inserted into the metal-nitrogen bond. The difference between the two types of metalloporphyrin carbene, and the conversion of one type to the other by oxidation in the case of iron, has been considered in a theoretical study. The comparison is especially interesting for the iron(ll) and cobalt(lll) carbene complexes Fe(Por)CR2 and Co(Por)(CR2) which both contain metal centers yet adopt... 

Six-coordinate organoiron porphyrin nitrosyl complexes, Fe(Por)(R)(NO), were prepared from Fe(Por)R (Por = OEP or TPP R = Me, n-Bu, aryl) with NO gas. The NMR chemical shifts were typical of diamagnetic complexes, and the oxidation state of iron was assigned as iron(ll). ... 

The reduced alkyl complexes are reoxidized by O2 to the iron(lll) alkyls. The corresponding diamagnetic phthalocyanine iron(ll) alkyl complexes, rFe(Pc)R), were prepared by two-electron reduction of Fe(Pc) by LiAIFl4 to give [Fe(Pc) (actually the Fe(I) phthalocyanine radical anion) followed by reaction with Mel, Etl or i-PrBr. The methyl compound, [Fe(Pc)CHi] was characterized by X-ray crystallography. ... 

One-electron reduction of the iron(lll) alkyl complexes forms the diamagnetic iron(ll) alkyl anions [Fe(Por)R. The iron(ll) anions do not react with oxygen directly, but are first oxidized by O2 to the corresponding alkyliron(III) complexes, Fe(Por)R, which then insert O2 as described above. 

Iron(II) alkyl anions fFe(Por)R (R = Me, t-Bu) do not insert CO directly, but do upon one-electron oxidation to Fe(Por)R to give the acyl species Fe(Por)C(0)R, which can in turn be reduced to the iron(II) acyl Fe(Por)C(0)R]. This process competes with homolysis of Fe(Por)R, and the resulting iron(II) porphyrin is stabilized by formation of the carbonyl complex Fe(Por)(CO). Benzyl and phenyl iron(III) complexes do not insert CO, with the former undergoing decomposition and the latter forming a six-coordinate adduct, [Fe(Por)(Ph)(CO) upon reduction to iron(ll). The failure of Fe(Por)Ph to insert CO was attributed to the stronger Fe—C bond in the aryl complexes. The electrochemistry of the iron(lll) acyl complexes Fe(Por)C(0)R was investigated as part of this study, and showed two reversible reductions (to Fe(ll) and Fe(l) acyl complexes, formally) and one irreversible oxidation process."" ... 

There are very few examples of asymmetric synthesis using optically pure ions as chiral-inducing agents for the control of the configuration at the metal center. Chiral anions for such an apphcation have recently been reviewed by Lacour [19]. For example, the chiral enantiomerically pure Trisphat anion was successfully used for the stereoselective synthesis of tris-diimine-Fe(ll) complex, made configurationally stable because of the presence of a tetradentate bis(l,10-phenanthroline) ligand (Fig. 9) [29]. Excellent diastereoselectivity (>20 1) was demonstrated as a consequence of the preferred homochiral association of the anion and the iron(ll) complex and evidence for a thermodynamic control of the selectivity was obtained. The two diastereoisomers can be efficiently separated by ion-pair chromatography on silica gel plates with excellent yields. 

An iron(lV)-imido complex was reported by Que and coworkers in 2006 [35]. The starting iron(ll) precursor is [Fe(N4Py)] (N4Py = V,V-bis(2-pyridylmethyl)bis... 

A dinuclear iron(ll/Ill) complex bearing a hexadentate phenol ligand displayed moderate activity toward aziridination of alkenes with PhlNTs a large excess of alkene (2,000 equiv. vs PhlNTs) was required for good product yields (Scheme 22) [76]. It is noteworthy that complex 4 is active in the aziridination of aliphatic alkenes, affording higher product yields than copper (11) catalysts with tetradentate macrocyclic ligands [77]. 

During the induced reactions involving peroxydisulphate in the presence of oxygen, the induced oxidation of iron(II) by oxygen can be observed just as with the hydrogen peroxide-iron(ll) system. Chloride and particularly bromide ions are effective inhibitors in the iron(II)-peroxydisulphate system. 

---