Paramagnetic fluorides

Elwell, D. t F nuclear resonance in some paramagnetic fluorides. Proc. Phys. Soc. 84, 409 (1964). 

Very large hyperfine interactions. A number of paramagnetic fluorides exhibit extremely large central-atom hyperfine interactions, e. g. 1576 G for in AsFa(12), 6200 G for jp,... 

The only important compound is the paramagnetic silver(II) fluoride, AgFj, prepared by fluorination of the metal it is used as a convenient fluorinating agent. 

Fluoride complexes of silver(III) are exemplified by the purple-red Cs2KAgF6 (elpasolite structure, octahedral Ag3+ paramagnetic with /x = 2.6/ub). Yellow MAgF4 (M = Na, Rb, K) and XeF AgF4 are diamagnetic and probably square planar [65],... 

Jaccarino, V., and if. G. Shulman Nuclear magnetic resonance in paramagnetic iron group fluorides. Phys. Rev. 106, 602 (1957). 

R. M. Kowalczyk, T. F. Kemp, D. Walker, K. J. Pike, P. A. Thomas, J. Kreisel, R. Dupree, M. E. Newton, J. V. Flanna and M. E. Smith, A variable temperature solid-state nuclear magnetic resonance, electron paramagnetic resonance and Raman scattering study of molecular dynamics in ferroelectric fluorides. /. Phys. Condens. Matter, 2011, 23, 315402. 

In certain cases, distortion may be imposed by the crystal structure. Nickel and palladium(II) fluorides have the rutile structure (16, 18, 239) in the nickel salt the fluoride octahedron is slightly flattened, whereas in palladium(II) fluoride, it is elongated. The metal-fluorine distances are shown in Table VIII. The fluoride is, incidentally, the only paramagnetic... 

Platinum(II) compounds are to be found only towards the bottom of this scheme, palladium(II) reaches further up, its fluoride belonging to the tetragonal, paramagnetic class. Nickel(II) complexes cover the whole range of behavior, and may in addition be tetrahedral. 

Although manganese catalases have often been referred to as azide insensitive/ these enzymes actually are inhibited by azide and related molecules albeit at higher concentrations than are necessary for the heme enzymes. Penner-Hahn and co-workers (22) have shown that HN3 is the likely protonation state of the inhibitor and have calculated an apparent of 80 mM. Slope replots of the pH dependence of azide inhibition are linear with a slope of 1. These data can be used to calculate a true K of 300 mM. Because azide is a competitive inhibitor with respect to peroxide, it is likely that azide is bound directly to the manganese center. Recent EPR and lH paramagnetic relaxation enhancement studies support this viewpoint. Other inhibitors include fluoride and thiocyanide. All of the reported inhibition studies are consistent with the catalase cycle and hydroxylamine inhibition of the catalase cycle. 

The pentafluorides are made by direct fluorination of the metals or the pentachlor-ides. Both are volatile white solids (Nb mp 80°C, bp 235°C Ta mp 95°C, bp 229°C), giving colorless liquids and vapors. They have the tetranuclear structures shown in Fig. 18-B-3. Niobium(IV) fluoride is a black, nonvolatile, paramagnetic solid TaF4 is unknown. 

Properties of Potassium Hexafluoroplatinately).—This salt is mustard yellow. A sample containing some iodine, possibly as iodyl fluoride, was paramagnetic. The low value of the magnetic moment, p = 0-87 B.M. (at 23°), may, in part at least, be due to this impurity. An infrared spectrum, of a Nujol mull, recorded with sodium chloride and cmsium bromide optics, showed two broad, overlapping, absorption bands, with peaks at 590 and 640 cm.. X-Ray powder photographs of the salt have been indexed on the basis of a rhombohedral unit-cell, a = 4-96 A, a = 97-4°, U = 119 9 A. The observed and calculated values for 1/df are given in Table 5. The solid can be stored indefinitely in well-dried, sealed tubes but decomposes... 

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