Sulfur hexafluoride, oxidation state elements

Most chemical properties of technetium are similar to those of rhenium. The metal exhibits several oxidation states, the most stable being the hep-tavalent, Tc +. The metal forms two oxides the black dioxide Tc02 and the heptoxide TC2O7. At ambient temperature in the presence of moisture, a thin layer of dioxide, Tc02, covers the metal surface. The metal burns in fluorine to form two fluorides, the penta- and hexafluorides, TcFs and TcFe. Binary compounds also are obtained with other nonmetaUic elements. It combines with sulfur and carbon at high temperatures forming technetium disulfide and carbide, TcS2 and TcC, respectively. 

In my work with sulfur tetrafluoride, I had found how simply one could obtain the lower oxidation-state fluoride, SF4, even though the hexafluoride, SFe, was easily preparable with additional fluorine. It was likely, I believed, that a range of oxidation states would similarly be available for many of the elements. What was already clear from my early work (see Chap. 1) was the likelihood that the late transition-series elements (such as platinum) could offer a range of oxidation states ranging down from Pt to perhaps Pt How the nature of the bonding would change in such a series, was a matter of great interest to me (see Chap. 6). Certainly the fluorides of... 

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. 

Both Mo and W have a wide variety of stereochemistries in addition to the variety of oxidation states, and their chemistry is among the most complex of the transition elements. Uranium has sometimes been classed with Mo and W in Group VI, and indeed there are some valid, though often rather superficial, similarities the three elements form volatile hexafluorides, oxide halides and oxo anions which are similar in certain respects. There is little resemblancefirthe sulfur group except in regard fief stoichiometric similarities, for example, SeF6, WF6, SO , MoOj", and such comparisons are not profitable. 

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