SeF4, Selenium tetrafluoride

The tetrafluorides of selenium and tellurium are similar to SF4 both structurally (in the gaseous molecules) and in terms of reactivity, ffowever, the bonding in condensed phases is different and leads to several types of structures. Selenium tetrafluoride can be prepared by combining the elements, but it can also be obtained by the reaction of Se02 with SF4 at high temperature. The tellurium compound can be prepared by the reaction of SeF4 and Te02 at 80 °C. 

The SeF4 molecule has a distorted structure similar to that of SF4, and its dipole moment is 1.78 D. Chemically, the tetrafluorides of Se and Te behave in much the same way as SF4. Selenium tetrafluoride can be prepared by direct combination of the elements or by the reaction of SF4 with Se02 at elevated temperatures. Tellurium tetrafluoride can be prepared by the reaction of SeF4 and Te02 at 80 °C. 

The 1 1 chlorine trifluoride-platinum pentafluoride adduct, m. p. I7l , and the 1 1 iodine pentafluoride adduct, m. p. 140° resemble, in their physical properties, the selenium tetrafluoride adducts of osmium pentafluoride (SeF4,OsFg, m. p. 158°) and iridium pentafluoride (SeF. IrFg, m. p. 133°). They are probably bifluorine-bridged monomers ... 

SeF4[g] SELENIUM TETRAFLUORIDE (GAS) 1475 SI2V 2-SILICON VANADIUM 1525... 

The vibrational spectra of (a) selenium tetrafluoride in the vapour and solid phases, and isolated in inert-gas matrices, and (6) tellurium tetrafluoride, in both the solid and matrix-isolated condition, have been reported. The fundamental frequencies were assigned on the basis of the symmetry of discrete SeF4 and Tep4 molecules force constants, obtained by normal-coordinate analysis, showed that the axial bonds are weaker than the equatorial... 

Selenium tetrafluoride, SeF4, is a colorless liquid. It has a vapor pressure of 757 mmHg at 105°C and 522 mmHg at 95°C. What is the heat of vaporization of selenium tetrafluoride ... 

Selenium Fluorides.—Two iluorides of selenium have been described, the hexafluoride, SeF6, and the tetrafluoride, SeF4. The former was obtained as a stable gas by the action of fluorine on selenium at 78° C.5 Its boiling-point, melting-point and critical temperature are —84-5° C. (in a sealed tube), —39° C. and +72° C., respectively. The vapour density, 97-28, agrees with the formula SeF8.6 The gas does not attack glass. 

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