Sulfur hexafluoride anion

Analysis of the halohydrocarbons, halocarbons, and sulfur hexafluoride is usually achieved by gas chromatography that is equipped with an electron capture detector. Complex metal anions, such as cobalt hexacyanide, are used as nonradioactive tracers in reservoir studies. The cobalt in the tracer compound must be in the complex anion portion of the molecule, because cationic cobalt tends to react with materials in the reservoir, leading to inaccurate analytic information [1226]. 

Fig. 3.10 Point groups and molecules of high symmetry (a) icosahedron, (b) the BuHff ion, (c) octahedron, (d) sulfur hexafluoride, (e) hexacyanocobaltateUlI) anion, (f) tetrahedron, (g) ammonium cation, and (h) tetrafluoroborate anion.

Elements with high values of E are present as anions in compounds with metallic elements and commonly have negative oxidation states in covalent compounds with other nonmetallic elements. For example, F has an oxidation state of-I in sulfur hexafluoride, SF6. 

Uranium has sometimes been classed with Mo and W in Group 6, and indeed there are some valid, though often rather superficial, similarities the three elements form volatile hexafluorides, oxide halides, and oxo anions that are similar in certain respects. There is little resemblance to the sulfur group except in regard to stoichiometric similarities (e.g., SeF6, WF6, SO4, and MoO -), and such comparisons are not profitable. 

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