Iron II Compounds

The authors of this book consider it appropriate to include in this section two contributions from their own laboratories, one on Mossbauer spectroscopy of spin crossover (SCO) phenomena in iron(II) compounds and the other on applications to biological systems. Both chapters will demonstrate the effectiveness of Mossbauer spectroscopy in these particular fields. 

Giitlich and Jung (1995) Thermal and optical switching of iron(II) compounds [234]. 

Giitlich, Spiering and Hauser (1999) Spin transition in iron(II) compounds [241]. 

Giitlich P, Spiering, H, Hauser A (1999) Spin transition in iron(II) compounds. In Solomon El, Lever ABP (eds) Inorganic electronic structure and spectroscopy, vol. II. Wiley, New York, p 575... 

The mononuclear hexakis(l-alkyl-tetrazole)iron(II) compounds with various anions have been extensively studied. It appears that the spin crossover characteristics of compounds with different alkyl substituents attached to N-1 of the tetrazole heavily depend on the crystal structure features. The transitions may be abrupt or rather gradual, complete or only involving a fraction of the Fe(II) ions, and the Tm values lie in the range 63-204 K [2c, 2f, 2g, 74-81]. Interest in these systems has focused on their suitability for detailed studies of the LIESST effect (A. Hauser, this volume). 

Dissertation Washington University St. Louis, 1979]. From data for the analogous cobalt(III) complex with perchlorate and hexafluorophosphate as anions, he found association constants of about 900 and 300, with distances of closest approach of 5 or 6 8, respectively. These values seem reasonable. For the iron(II) compound with the hexafluorophosphate or perchlorate, the ion association constants were too small to measure (< - 50). 

The iron(II) compounds [FeL2](C104)2 MeCN, [FeL2](BPh4)2 2MeCN and [FeL2](PF6)2, where L is the terdentate ligand 2,6-bis(3,5-dimethylpyrazol-l-ylmethyl)pyridine, all show temperature-... 

Calcium fluoride Iron (II) compounds Copper (I) oxide Manganese (TV) oxide... 

IRC (intrinsic reaction coordinate analysis), 45 Iridium oxide, amperometry, 650 Iron(II) compounds... 

Figure 16 shows the spectra obtained for two other pigments— green earth and Prussian blue. In the former case there are actually two spectra, one of which consists of a widely split doublet typical of iron (II) compounds. Heating this pigment changes it to a brownish-red and removes the ferrous doublet. 

In the Mossbauer spectra of the Fe(R2Dtc)3 complexes, simple quadruple split doublets are observed that are interpreted as the weighted means of the high-spin and low-spin forms (153). It has been pointed out (454) that a rapid transition (>10 7 sec) is not characteristic for complexes with different spin states, and indeed two doublets are observed in the Mossbauer spectra of iron(II) compounds with temperature-dependent magnetic moments. The same... 

Today several methods are known, which can be classified into two types, depending on whether they involve the reduction of iron(II) compounds or ligand substitutions on iron(0) complexes. 

The richest dietary sources of total iron are organ meats (liver and kidney), egg yolk, dried legumes, com, molasses and parsley. Liver is particularly valuable because of the high absorbability of its iron. However, only about 10% of dietary iron is absorbed. Iron deficiency anemia can be treated with soluble iron(II) compounds providing 200 mg in three or four daily divided doses. Oral iron(II) sulfate is the least expensive and is in wide use. Ascorbic acid increases the absorption efficiency of iron(II) sulfate. Parenteral administration of iron is used when oral iron is ineffective. Iron-dextran, a colloid formed from iron(III) chloride and an alkali-modified dextran, is one of several preparations available which has found extensive clinical use. It contains up to 28% Fe by weight and has a structural similarity to ferritin. Transfusion therapy may also be used in severe chronic anemia or acute hemorrhage. 

Isocyanides have been used to probe the bonding sites in hemoproteins and related compounds (215-219). Additions of CNCH2Ph, PBu , and P(OEt)3 to Fe(II)cap (cap = dianion of capped porphyrine) has produced five-coordinate low-spin iron(II) compounds by jr-acid destabilization of the dz2 orbital of the iron(II) porphyrin (215). 

The literature on iron (II) compounds exhibiting spin crossover has been tabulated according to the keywords given below. R in a column means that the corresponding physical method has been applied at room temperature only. 

Iron (II) formate can be prepared by the action of formic acid on pure iron or by a number of double-displacement reactions.1 The method based on the reaction of iron with acid was adopted because of the ease of isolating the final product and of preventing the oxidation of the iron (II) compound. Care must be taken along two lines contact of the solutions or wet salt with air must be minimized, and an excess of acid must be present in the aqueous solutions. 

Ancient alchemists liked to use strong sulfuric acid to produce dramatically dangerous effects. One interesting reaction occurs when sulfuric acid reacts with iron metal to produce gas and an iron(II) compound. What volume of gas is produced when excess sulfuric acid reacts with 40.0 g of iron at lS.O C and 100.3 kPa ... 

Reactants sulfuric acid and iron Products an iron(II) compound and a gas Mass of iron = 40.0 g Temperature = 18.0°C Pressure = 100.3 kPa... 

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