Cobalt trifluoride, structure

Crystallographic data (.continued) for transition metal tetrafluorides, 27 98 for transition metal trifluorides, 27 92 Crystallographic disorder, nitrosyl groups, 34 304-305 Crystallography fuscoredoxin, 47 380 prismane protein, 47 232-233 Rieske and Rieske-type proteins, 47 92-109 Crystal radii, of various ions, 2 7 Crystals, 39 402 Crystal structure actinide metals, 31 36 copper-cobalt supetoxide dismutases, 45 ... 

In contrast with the difluorides, the distribution of trifluorides extends to the third series of the transition metals, where iridium and gold trifluorides are fully characterized. In the second series, trifluorides are known for the elements from niobium to rhodium, with the exception of technetium, and in the first series, from titanium to cobalt. All the trifluorides have been characterized structurally, with earlier reports based on X-ray powder-diffraction data, since the compounds were not prepared in single-crystal form until more recently, when high-temperature, crystal-growth techniques became available. 

A comparison of the volumes per formula unit for the trifluorides is more complicated than for the difluorides because of the changes in structure type. If these changes are ignored, then some correlation with electronic configuration is possible. For the first transition series the volume decreases from scandium to chromium, increases from chromium to iron, and decreases to cobalt. This is as expected for the characteristic ligand-field stabilization effects (49), comparable with those for the difluorides. In the second series, there is a decrease from... 

Although attempts have been made to prepare other fluorides with this stoichiometry, for example, by the interaction of the di- and trifluorides of iron and cobalt (54), these have been unsuccessful. For vanadium, the compound VF2, presumably contains vanadium(III) but the structure remains that of rutile, with a maximum 8 value of 0.04 (18 ). 

Nickel compounds can also be employed as catalysts [161-170]. A three-component system consisting of nickel naphthenate, triethyl-aluminum, and boron trifluoride diethyletherate is used technically. The activities are similar to those of cobalt systems. The molar Al/B ratio is on the order of 0.7 to 1.4. Polymerization temperatures range from -5 to 40 °C. On a laboratory scale the synthesis of 1,4-polybutadiene with allylchloronickel giving 89% cis, 7.7% trans, and 3.4% 1,2-structures is particularly simple [8]. In nickel compounds with Lewis acids as cocatalysts, complexes with 2,6,10-dodecatriene ligands are more active than those with 1,5-cyclooctadiene (Table 4) [171]. 

An alternative approach to structures similar to (122) involves initial construction of the saturated ring followed by a lactonization sequence. Meyers and Avila have described the conversion of naphthyloxazolines into lignan lactone derivatives with the same basic structure as (12 ). Bislactone lignans are obtained by the instantaneous oxidative dimerization of p-alkoxycinnamic acids with thallium(iii) trifluoroacetate or cobalt(iii) trifluoride. Although the yields are only between 12 and 54%, the method provides a convenient entry into these complicated structures. ... 

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