Technetium hexafluoride

Technetiumhexafluorid

Golden yellow crystals

Fixed

3.58 g · cm -3 ( -140 ° C)

37.4 ° C

55.3 ° C

4616.84 ± 1.60 J · mol -1

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Technetium (VI ) fluoride ( TcF6 ), usually also Technetiumhexafluorid, is an inorganic compound of the elements technetium and fluorine and belongs to the group of hexafluoride. It is a golden yellow crystalline solid with a low melting point and boiling point. In this connection, technetium is in the oxidation state 6, the highest of the Technetiumhalogenide. The other compound is the technetium hexavalent (VI ) chloride, TcCl6. In this respect, differs from technetium, rhenium, forming the Heptafluorid REF7 in its highest oxidation state. Since technetium is a cleavage product of the uranium occurs as Technetiumhexafluorid Verunreiningung of uranium hexafluoride.

Representation

Technetiumhexafluorid represented by direct reaction of the metal in an excess of elemental fluorine (F2), at 400 ° C.

Properties

Physical Properties

Technetiumhexafluorid is a golden yellow crystalline solid which melts at 37.4 ° C and boils at 55.3 ° C. At -4.54 ° C, a solid phase transition is observed. Above this temperature ( measured at 10 ° C), it crystallizes in the cubic crystal system with the lattice parameters a = 616 pm and two formula units per unit cell with a calculated density of 3.02 g · cm -3. Below this temperature (measured at -19 ° C) crystallizes in the orthorhombic crystal system, space group Pnma with the lattice parameters a = 955 pm, b = 874 pm and c = 502 pm and four formula units per unit cell with a calculated density of 3.38 g · cm -3. The lattice parameters of the orthorhombic phase be at -140 ° C: a = 936.0 pm, b = 851.7 pm and c = 493.4 pm with a calculated density of 3.58 g · cm -3.

Show IR and Raman spectroscopy, that the molecule is TcF6 octahedral (Oh ); the Tc -F bond length is 181.2 pm. Magnetic-moment measurements give a value of 0.45 mB.

Chemical Properties

With iodine in iodine pentafluoride solutions TcF6 reacts quantitatively TcF5. Alkali metal chlorides in iodine pentafluoride solution it reacts to Hexafluorotechnetaten ( TcF6 ). TcF6 disproportionated upon hydrolysis with aqueous NaOH and forms a black precipitate of technetium (IV ) oxide TCO2, which dissolves on addition of hydrogen peroxide H2O2. In hydrogen fluoride solution TcF6 reacts with Hydraziniumfluorid to N2H6TcF6 or N2H6 ( TcF6 ) 2