Sulfur oxofluorides

The SO2 molecule contains two more valence electrons than CO2. If the stracture had been linear, the two additional electrons would have had to enter a 3c antibonding n orbital. When the molecule bends and the S atom is rehybridized, the three n orbitals in the molecular plane are converted into the three non-bonding a orbitals indicated at the left of Fig. 20.3. 

Sulfur forms one oxofluoride in which the S atom is tetravalent and two oxofluorides in which it is hexavalent. See Fig. 20.5. The S=0 bond distance in OSF2 is about 3 pm shorter than in SO2, the S-F bond distances 1 or 2 pm shorter than the mean S-Fbond distance in SF4. The S=0 bond distances in O2SF2 or OSF4 are 1 or 2 pm shorter than in SO3, the S-F bond distances in the former are about 3 pm shorter than, the S-F bond distances in the 

The energies of atomization of the three molecules calculated from their enthalpies of formation are [4] 

If we assume the SO bond energy in OSF2 to be equal to the MBE in SO2 and the mean S-F bond energy to be equal to the mean bond energy in SF4, we obtain an estimated atomization energy of OSF2 (1206 kJ moP ) which reproduces the experimental value with a deviation of just 1 %. Similarly transfer of bond energies from SO3 and SF6 leads to 

Problem 20.2 Draw Lewis structures of the three sulfur oxofluorides in Fig. 20.5. Are the structures in agreement with the VSEPR model  

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Sulfur forms two main series of oxohalides, the thionyl dihalides OS X2 and the sulfuryl dihalides 02S X2. In addition, various other oxofluorides and peroxofluorides are known (p. 688). Thionyl fluorides and chlorides are colourless volatile liquids (Table 15.14) OSBt2 is rather less volatile and is orange-coloured. 

For Se only Se02F2 is known. For Te there are no Te02X2 compounds, but recently TeOF2 and Te have been reported. The structure of TeOF2 is unknown but Te d has a complex polymeric structure. Both selenium and tellurium, as well as sulfur, form a number of more complex oxofluorides, a few of which are shown, with their structures, where known, in Table 12-7. 

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