Sulfur hexafluoride bonding

Thus the bonding in sulfur hexafluoride SF6 has for a long time been considered to involve two of the 3d orbitals of sulfur, with the sulfur in a sp3d2 hybridized state and... 

A sulfur hexafluoride molecule, SF6, has six atoms attached to the central S atom and no lone pairs on that atom (8). According to the VSEPR model, the electron arrangement is octahedral, with four pairs at the corners of a square on the equator and the remaining two pairs above and below the plane of the square (see Fig. 3.2). An F atom is attached to each electron pair, and so the molecule is predicted to be octahedral. All its bond angles are either 90° or 180°, and all the F atoms are equivalent. 

Sulfur hexafluoride Oh). Six sulfur-fluorine cr bonds require 2 electrons in the valence shell. Six equivalent bonds require an octahedron and so sulfur wjU be hybridized sp d2 as shown in Fig. 6.lf. 

As was true in the case of five charge clouds, different shapes are possible for molecules having atoms with six charge clouds, depending on whether the clouds are of bonding or nonbonding electrons. Sulfur hexafluoride, for example, has all six positions around sulfur occupied by fluorine atoms ... 

This also proves an earlier conclusion on hyperconjugation in an 0CH20 fragment of the 1,3-dioxolane cation radical this conclusion was based on mass spectrometry (To-dres, Kukovitskii et al. 1981). As calculated, the carbon-hydrogen bonds corresponding to 0CH20 in the radical cation are weaker than those in the neutral molecule. For this reason, this site exhibits a maximal probability that deprotonation will result in the formation of the 2-yl radical (Belevskii et al. 1998). In experiments, photoirradiation of 1,3-dioxolane solutions in sulfur hexafluoride at 77 K really leads to formation of the cation radical of 1,3-dioxolane and the l,3-dioxolan-2-yl radical as a result of deprotonation. Consecutive ring... 

We may represent the formation of sulfur hexafluoride, SFe, from sulfur in fluorine atoms in a similar manner. Here the coordination number is six—that is, six bonds are formed by the central atom. The 3s, 3p, and 3d orbitals will be concerned in bond formation ... 

Sulfur hexafluoride sublimes at -64 °C to produce a dense gas (6.14 g L-1). Under a pressure of 2 atm, the melting point is -51 °C. The molecule has the expected octahedral structure and a dipole moment of zero. The compound is so inert that it is used as a gaseous insulator, and rats allowed to breathe a mixture of SF6 and oxygen show no ill effects after several hours of exposure. This inertness is a result of the molecule having no vacant bonding site or unshared electron pairs on sulfur to initiate a reaction and the fact that six fluorine atoms shield the sulfur atom from attack. Consequently, there is no low-energy pathway for reactions to occur, and the compound is inert even though many reactions are thermodynamically favored. 

The molecule sulfur hexafluoride SF6 exemplifies one of the most common types of d orbital hybridization. The six bonds in this octahedrally-coordinated molecule are derived from mixing six atomic orbitals into a hybrid set. The easiest way to understand how these come about is to imagine that the molecule is made by combining an imaginary S6+ ion (which we refer to as the S(VI) valence state) with six F ions to form the neutral molecule. These now-empty 3s and 3p orbitals then mix with two 3d orbitals to form the sp3d2 hybrids. 

Sulfur, unlike oxygen, has the capacity to expand its valence shell beyond the normal octet of electrons to form hypervalent compounds such as sulfur tetrafluoride (SF4) with 10 electrons in the outermost shell and sulfur hexafluoride (SF6) containing 12 electrons in the valence shell.63,7 The chemistry of hypervalent sulfur started in 1873 with the discovery of the unstable compound sulfur tetrachloride (SCI4). The existence of hypervalent sulfur compounds is an important feature of the chemistry of sulfur and the precise nature of the bonding in these molecules has remained a puzzling problem. 

Describe the intermolecular forces that are present in each of the following compounds. Which kind of force would have the greatest influence on the properties of each compound (a) ethyl alcohol, C2HgO (contains one C—O single bond) (b) phosphine, PH3 (c) sulfur hexafluoride, SFg. 

Many molecules are known in which a central atom forms bonds with six other atoms that are arranged about it at the corners of a regular octahedron. An example is sulfur hexafluoride, SF6. In this octahedral molecule the sulfur atom uses the six electrons of its outer shell to form six bonds, one with each of the six fluorine atoms. This molecule is described as involving octahedral coordination of the six fluorine atoms about the sulfur atom or octahedral ligation of the six fluorine atoms to the sulfur atom. 

The molecule sulfur hexafluoride (SFA has recently challenged both molecular spectroscopy with its unexpected rotational spectra 29) and electronic structure theories with novel correlation effects (30,31,5). The electronic structure must explain the molecule s high stability, octahedral symmetry, and, most importantly, provide a simple picture of the bonding. At first glance, the traditional chemical models do not appear to be appropriate because sulfur seemingly forms six bonds to fluorines, yet the sulfur s2pA valence configuration allows for at most two covalent bonds. 

Sulfur hexafluoride is a nontoxic, colorless gas (b.p. -63.8°C). It is the most inert of all sulfur compounds it resists attack even by molten KOH. The structure and bonding of SFg were discussed in Chapters 9 and 10 and its critical phenomenon illustrated in Chapter 11 (see Figure 11.37). 

Sulfur hexafluoride (4.5) provides an example of a so-called hypervalent molecule, i.e. one in which the central atom appears to expand its octet of valence electrons. However, a valence bond picture of the bonding in SFg involving resonance structures such as 4.6 shows that the S atom obeys the octet rule. A set of resonance structures is needed to rationalize the observed equivalence of the six... 

One example is sulfur hexafluoride, SF5, a remarkably dense and inert gas used as an insulator in electrical equipment. The central sulfur is surrounded by six single bonds, one to each fluorine, for a total of 12 electrons ... 

With six bonding groups, the molecular shape is octahedral (AXg), as in sulfur hexafluoride (SFg) ... 

Sulfur hexafluoride is sold in cylinders containing 100 lb of the material at about 3 per lb (1959 price). It is used as the electrical insulator in coaxial cables, high voltage X-ray transformers, and high voltage generators (35, 211). Its availability is a stimulus to research dealing with the substance. Many studies use the substance because it is inert or because it is made up of nearly spherical molecules. There is also much theoretical interest in its structure and in the nature of the chemical bond involved. Many studies are related to its usefulness as an electrical insulator. 

Atoms of the second-period elements cannot have more than eight valence electrons around the central atom, but atoms of elements in and beyond the third period of the periodic table form some compounds in which more than eight electrons surround the central atom. In addition to the 3s and 3p orbitals, elements in the third period also have 3d orbitals that can be used in bonding. These orbitals enable an atom to form an expanded octet. One compound in which there is an expanded octet is sulfur hexafluoride, a very stable compound. The electron configuration of sulfur is [Ne]3 3p" . In SFg, each of sulfur s six valence electrons forms a covalent bond with a fluorine atom, so there are 12 electrons around the central sulfur atom ... 

---