Fluoro-complexes

Godneva and D. L. Motov, The Chemistry of Fluoride Compounds of Zirconium and 

Chloro-, Bromo-, and lodo-complexes. The effect of pressure on the kinetics of the reaction between solid NaCl and ZrC or HfCl4 vapours has been investigated. The i.r. and Raman spectra of solid ZrCl4,2NOCl and HfCl4,2NOCl have shown that they consist of NO and octahedral hexachlorometallate ions. °° Normal-co-ordinate analyses have been reported for the [ZrX ] and [HfXg] ions (X = Cl or Br). °  

Zrl4 vapour reacts rapidly and reversibly with metallic copper and silver (M) at ca. 200°C to give thick, velvet-like scales of Mq 2sZro.75l3, which are considered to be pseudo-trihalides. Hfl4 vapour only reacts to a small extent with copper and not at all with silver.  

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Solvent extraction techniques are useful in the quantitative analysis of niobium. The fluoro complexes are amenable to extraction by a wide variety of ketones. Some of the water-insoluble complexes with organic precipitants are extractable by organic solvents and colorimetry is performed on the extract. An example is the extraction of the niobium—oxine complex with chloroform (41). The extraction of the niobium—pyrocatechol violet complex with tridodecylethylammonium bromide and the extraction of niobium—pyrocatechol—sparteine complex with chloroform are examples of extractions of water-soluble complexes. Colorimetry is performed on the extract (42,43). Colorimetry may also be performed directly on the water-soluble complex, eg, using ascorbic acid and 5-nitrosahcyhc acid (44,45). 

This oxidation state is sparse in the case of Mn but is important in the pharmaceutical applications of Tc, and an extensive chemistry has been developed. Some fluoro complexes of Tc and Re such as the salts of [MFe] are known, but oxo compounds predominate and, in [MOCls] and [MOX4] (X = Cl, Br, I) for instance, other halides are also able to coordinate. [MOX4] is square pyramidal with apical M=0 and the moiety is reminiscent... 

Halide complexes decrease markedly in stability from F to I . Fluoro complexes... 

M(N03)4] anions containing the unusual unidentate niirato ion are also known. Fluoro complexes are even less prevalent, the preference of these cations being for the other halides, cyanide, N- and heavy atom-donor ligands. 

In forming the fluoro complex [Aup4] mentioned above, and indeed in forming the simple fluoride AuFb, Au differs from the isoelectronic Pt since the corresponding [PtF4] and Ptp2 are unknown. 

The coordination chemistry of Zn" and Cd", although much less extensive than for preceding transition metals, is still appreciable. Neither element forms stable fluoro complexes but, with the other halides, they form the complex anions [MX3] and [MX4] , those of Cd" being moderately stable in aqueous solution. "" By using the large cation [Co(NH3)6] + it is also possible to isolate the trigonal bipyramidal [CdCls] "... 

Tantalum is severely attacked at ambient temperatures and up to about 100°C in aqueous atmospheric environments in the presence of fluorine and hydrofluoric acids. Flourine, hydrofluoric acid and fluoride salt solutions represent typical aggressive environments in which tantalum corrodes at ambient temperatures. Under exposure to these environments the protective TajOj oxide film is attacked and the metal is transformed from a passive to an active state. The corrosion mechanism of tantalum in these environments is mainly based on dissolution reactions to give fluoro complexes. The composition depends markedly on the conditions. The existence of oxidizing agents such as sulphur trioxide or peroxides in aqueous fluoride environments enhance the corrosion rate of tantalum owing to rapid formation of oxofluoro complexes. 

Other RhX(CO)(PPh3)2 compounds can be made as shown in Figure 2.23 metathesis with an alkali metal halide or pseudohalide is often convenient, but the most versatile route, as with the iridium analogues, is a two-stage process in which the fluoro complex is first prepared, the fluorine then being readily displaced. 

Violet fluoro complexes like BaAgF4 and Cs2AgF4 can be made by fluorination... 

Walker, N., Wright R., Barren, P., Murrell, J. and Stace, A. (1997) Synthesis of Au(II) Fluoro Complexes and Their Structural and Magnetic Properties. Journal of the American Chemical Society, 119, 1020-1026. 

ZnxZryFz. A fluoro complex of zirconium, ZrF62, and an ammine complex of zinc, ZnfNFF), have been used to grow ZnxZryFz films on silicon. The Zn/Zr/F ratio was 0.08/1/0.32, and the films contained hydroxyl groups and physisorbed water.128... 

F NMR Data for Fluoro Complexes of Beryllium(II) in Aqueous Solution ... 

The stepwise formation of fluoro complexes in aqueous solution has been extensively studied in recent years by standard techniques (192). The introduction of the LaF3 electrode has enabled fluoride activities to be measured directly, even with the "insoluble fluorides such as CaF2 or PbF2 (34, 81). Values obtained depend on the salts added to maintain constant ionic strength, and care must be taken in making comparisons since not all results are extrapolated to zero strength (15). Key references to work in this field can be gleaned from standard compilations of stability constants. 

Hajhium. It is very similar to Zr. The best solvent is HF the formation of anionic fluoro-complexes is, also in this case, determinant in the stabilization of the solution. 

Dean,P. A. W., Evans, D. F. Spectroscopic Studies of Inorganic Fluoro-complexes. 

Indiuin(v).—Both crystal-field and charge-transfer bands have been observed in the diffuse reflectance spectrum of [IrF ]". Calculation of the spin-orbit coupling constant and crystal-field parameters indicated that the degree of covalency is high for a fluoro-complex, and comparable with that found for quadrivalent [MFg] species of the first transition series. ... 

At present, there are not sufficient data available for the change of enthalpy by formation of hydroxo complexes which are further complicated by precipitation and polynuclear behaviour. However, some of Julius Thomsen s calorimetric measmrements seem to indicate that heat frequently is evolved with hard central atoms in contrast to formation of the corresponding fluoro complexes. On the other hand, sulphate and carboxylates behave like F according to Ahrland. 

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