Halides
المؤلف:
Peter Atkins, Tina Overton, Jonathan Rourke, Mark Weller, and Fraser Armstrong
المصدر:
Shriver and Atkins Inorganic Chemistry ,5th E
الجزء والصفحة:
ص408-409
2025-09-25
331
Halides
Key points: The halides of oxygen have limited stability but its heavier congeners form an extensive series of halogen compounds; typical formulas are EX2, EX4, and EX6. The oxidation number of O is -2 in all its compounds with thشe halogens other than F. Oxygen difluoride, OF2, is the highest
fluoride of oxygen and hence contains O in its highest oxidation state (+2). The structures of the sulfur halides S2F2 , SF4, SF6, and S2 F10 (Table 16.3) are all in line with the VSEPR model. Thus, SF4 has ten valence electrons around the S atom, two of which form a lone pair in an equatorial position of a trigonal bipyramid. We have already mentioned the theoretical evidence that the molecular orbitals bonding the F atoms to the central atom in SF6 primarily use the sulfur 4s and 4p orbitals, with the 3d orbitals playing a relatively unimportant role (Section 2.11a). The same seems to be true of SF4 and S2F10. Sulfur hexafluoride is a gas at room temperature. It is very un-reactive and its inertness stems from the suppression, presumably by steric protection of the central S atom, of thermodynamically favourable reactions, such as the hydrolysis
The less sterically crowded SeF6 molecule is easily hydrolysed and is generally more reactive than SF6 . Similarly, the sterically less hindered molecule SF4 is reactive and undergoes rapid partial hydrolysis:
Both SF4 and SeF4 are selective fluorinating agents for the conversion of -COOH into CF3 and C=O and P=O groups into CF2 and PF2 groups:
Sulfur chlorides are commercially important. The reaction of molten S with Cl2 yields the foul-smelling and toxic substance disulfur dichloride, S2Cl2, which is a yellow liquid at room temperature (b.p. 138C). Disulfur dichloride and its fur ther chlorination product sulfur dichloride, SCl2, an unstable red liquid, are produced on a large scale for use in the vulcanization of rubber. In this process, S atom bridges are introduced between polymer chains so the rubber object can retain its shape.
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