FeOCl

In the CeSI (115) and NdSBr (334) type of structure, bromine and iodine are coordinated to five metal ions (four of the same layer, and one of the opposite layer) and four halogen ions of the double layer. In the SmSI type (335), iodine is coordinated to three metal ions of a [LS] layer and three other iodine ions of the double layer. In the FeOCl type of compound, such as ErSCl (355) and LuSBr (85), the halogen is surrounded by a polyhedron formed by six sulfur and four halogenide ions. 

Fig. 17. Tetragonal symmetry projective view (above) and cut A-B (below) of a [LS],-layer formed by a sequence of [L,S] tetrahedrons (ideally PbFCl-t3q)e distorted CeSI-, FeOCl-, and NdSBr-types). (Redrawn from C. Dagron and F. Thevet, Ann. Ckim. 6, 67 (1971), Fig. 6, p. 77.)...

M. G. Kanatzidis, M. Humbbard, L. M. Tonge, T. J. Marks, H. 0. Marcy, C. R. Kannewurf, In situ intercalative polymerization as a route to layered conducting polymer-inorganic matrix microlaminates, polypyrrole and polythiophene in FeOCl, Synthetic Metals, vol. 28, pp. 89-95,1989. 

Fig. 2 Crystal structure of FeOCl viewed perpendicularly to the b axis (left) and proposed arrangement of PANI chains in the galleries of FeOCl viewed from two different directions middle and right) (Reprinted from [32] with permission from ACS)...

As can easily be understood, the in situ polymerization process is favored when distances between monomers in the interlamellar space are close to the monomeric repeat distance displayed by the polymer. Such a compatibility of distances was first demonstrated for the polymerization of aniline in V2O5 and FeOCl hosts with an exact matching between NH functions for PANl and the (1-30) crystallographic direction for V2O5 or the (201) direction for FeOCl [63]. 

Other groups have achieved CNT forest assemblies by electrostatic SWNT-COO / Fe interactions also starting with shortened CNTs. The assembly process involves sequential substrate dipping in dilute Nafion and aqueous FeCl3 solutions followed by DMF-assisted precipitation of the nafion-adsorbed Fe to produce thin FeO(OH)/FeOCl nanocrystals. Subsequent immersion into a DMF disperse nanotube suspension produces the forest assembly that is driven by acid-base neutralization [12, 61, 121[. 

A number of researchers, ° ° particularly in Japan, have been pursuing the oxides of iron as potential cathode materials for lithium cells. However, materials of the type LiFeOz have shown little ability for lithium removal. A number of other iron compounds have been studied over the years, including FeOCl, ° FePS3, ° KFeSz, and FeSz, but none showed much reversibility. Although metal phosphates have been studied for more than 20 years since the discovery of fast ion transport in NASICON, it is only recently that they have been considered as cathodes or anodes " of lithium batteries. 

SEM studies supported the above in observation of platelet type crystals containing Fe and Cl (by EDAX). ESCA revealed little detail but SIMS identified a number of hydroxy and oxychloride species including Fe(0H)+, Fe0+, FeO-, FeOCl- and FeCl to support the presence of chloride in the pyroaurite type film. LIMA indicated a number Fe 0 + peaks with x as y as high as 2 or 3 X y... 

FeCl3,0.3H2O > FeClj > FeOCl. ° The reaction of BBr with anhydrous FeClj or anhydrous oxides of Fe gives anhydrous FeBrj. The structure of (4-EtpyH)[FeBr ] has been reported, the anion being tetrahedral. ... 

Organic molecules such as aniline, pyrrole and 2,2 -bithiophene have been intercalated and polymerized within the galleries of clay minerals, FeOCl, V2O5 gel and other layered hosts to yield multilayered inorganic/organic polymer nanocomposites... 

Ferric chloride combines with ether 6 to form a dark red, highly deliquescent solid of composition FeCl3.(C2H5)20. It is soluble in water and alcohol, and at 100° C. decomposes quantitatively, yielding the oxychloride FeOCl —... 

North, N. A., Pearson, C., Thermal Decomposition of FeOCl and Marine... 

The transition metal oxyhalides occur with four main structure types (FeOCl, AlOCl, SmSI, and PbFCl) but only the FeOCl structure undergoes topotactic redox reactions. A layer of the orthorhombic FeOCl structure is shown in Figure 21. The structure is characterized by double sheets of distorted octahedra that share edges. Each iron atom is coordinated to four oxide anions and two chloride ions, with the two chloride ions in cis octahedral positions on the outside of the layer. The arrangement of octahedra within a layer is similar to that found in y-FeOOH and y-AlOOH. 

Reactions with Lewis bases are the other major class of redox intercalation reactions that have been explored with the FeOCl lattice. Pyridine, for example, reacts with FeOCl to form two compounds, (py)i/4FeOCl and (pyji/sFeOCl. Reactions of FeOCl with ammonia and alkylamines are among the earliest reported intercalation reactions of compounds with neutral layers. ... 

Figure 21 The arrangement of atoms in a single layer of FeOCl...

FeOCl also shows a type of interlayer reactivity not found in other systems. Irreversible topochemical substitution reactions are observed where the outer hahde layers of the FeOCl lattice are replaced by other groups. Examples of this type of substitution were first observed in reactions of ammonia and methylamine with FeOCl at ambient temperature. Reaction occurs with two moles of ammonia or methylamine according to equation (12), where R = H or Me. The products of the... 

Other substitution reactions lead to more crystalline phases. Reaction of (4-aminopyridine)i/4FeOCl with methanol at 100 °C, for example, gives crystalline FeOOMe. Reactions with aliphatic and aromatic alkoxides and acids, of the type shown in equations (13) and (14), have also been studied. More rigid and longer molecules, such as 4-hydroxybenzoic acid, can crosslink the iron oxide layers. An initial intercalation step that causes an expansion of the FeOCl interlayer distance is followed by a second substitntion step leading to layer crosslinking. 

The MNX a-polymorphs adopt the FeOCl type layered structure (see Section 3.4) and exist for all combinations of MNX (M = Zr, Hf X = Cl, Br, I) and for TiNX (X = Cl, Br, I). Superconductivity at 11K is observed on intercalation of lithium in a-ZrNBr and a-ZrNI using BuLi. Intercalation of pyridine into TiNCl gives pyridinei/3 TiNCl, which superconducts at 4 6 K. The latter is reminiscent of the effect of intercalation of organic bases into the superconducting dichalcogenides. 

Kargin, 1928 Kargin and Kiseleva, 1938) believes that sols of Fe(OH)3 always contain a certain amount of hydrochloric acid which acts as the stabilizing electrolyte, and the positive charge of the granule is produced by adsorption of ions. The opinion prevailing at present is that the stabilizer is the product of incomplete hydrolysis of perchlorate of iron (FeOCl) formed according to the equation ... 

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