Bonding in SCl n ( n = 1−6): A Quantum Chemical Study

2014

Theor Chem Acc

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As first noted by Dixon et al. (J Am Chem Soc 108:2461-2462, heavily fluorinated pyramidal phosphorus compounds, e.g., F n PH (3-n) with n [ 1, invert through a T-shaped transition state (edge inversion) rather than the D 3h -like transition states (vertex inversion) found in the corresponding nitrogen compounds and less fluorinated phosphorus compounds. Subsequent studies by Dixon and coworkers established that this is a general phenomenon and has important chemical consequences. But what is the reason for the change in the structure of the transition state? Recent theoretical investigations have resulted in the discovery of a new type of chemical bond, the recoupled pair bond. In particular, it was found that recoupled pair bond dyads account for the hypervalency of the elements beyond the first row. In this paper, we show that recoupled pair bond dyads also account for the existence of the edge inversion pathway in heavily fluorinated phosphorus compounds and likely account for the presence of the lower energy inversion pathways in pyramidal compounds of other elements beyond the first row.

Section: Gvb Orbitals Of the Transition Statessupporting

confidence: 90%

Section: Further Comparison Of S-and P-recoupled Pair Bond Dyadsmentioning

confidence: 55%

Section: Gvb Orbitals Of the Transition Statesmentioning

confidence: 99%

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Why edge inversion? Theoretical characterization of the bonding in the transition states for inversion in F n NH(3−n) and FnPH(3−n) (n = 0–3)

Takeshita

2014

Theor Chem Acc

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“…5 Previous studies of the halides of the second row, late p-block elements, by our group have shown that hypervalent or hypercoordinated molecules possess a previously unrecognized type of bond, a recoupled pair bond. [6][7][8][9][10][11][12][13][14] Recoupled pair bonds and recoupled pair bond dyads 14 the stability of SF 4 and SF 6 , 7 as well as other hypervalent species such as PF 5 , 9 ClF 3 , and ClF 5 , 8 providing a simple, straightforward explanation of the low-lying states, structures, and energetics of these species as well as those of the intermediate SF n , PF n , and ClF n radicals. In fact, it has been found that the ability of elements beyond the first row to form recoupled pair bonds accounts for a number of the differences between the structures, energetics, and spectra of compounds of the first and second row elements, including differences in reactivity 13 -the so-called first-row anomaly.…”

Section: Introductionmentioning

confidence: 99%

Fundamental aspects of recoupled pair bonds. I. Recoupled pair bonds in carbon and sulfur monofluoride

The Journal of Chemical Physics

Takeshita

2015

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The number of singly occupied orbitals in the ground-state atomic configuration of an element defines its nominal valence. For carbon and sulfur, with two singly occupied orbitals in their 3P ground states, the nominal valence is two. However, in both cases, it is possible to form more bonds than indicated by the nominal valence—up to four bonds for carbon and six bonds for sulfur. In carbon, the electrons in the 2s lone pair can participate in bonding, and in sulfur the electrons in both the 3p and 3s lone pairs can participate. Carbon 2s and sulfur 3p recoupled pair bonds are the basis for the tetravalence of carbon and sulfur, and 3s recoupled pair bonds enable sulfur to be hexavalent. In this paper, we report generalized valence bond as well as more accurate calculations on the a4Σ− states of CF and SF, which are archetypal examples of molecules that possess recoupled pair bonds. These calculations provide insights into the fundamental nature of recoupled pair bonds and illustrate the key differences between recoupled pair bonds formed with the 2s lone pair of carbon, as a representative of the early p-block elements, and recoupled pair bonds formed with the 3p lone pair of sulfur, as a representative of the late p-block elements.

“…But, there are alternative descriptions of the SO bond in the sulfinyls. [52]. In short, the two SCl bonds comprise a r recoupled pair bond dyad, where both Cl atoms form bonds to the 3p 2 pair of the S( 3 P) atom.…”

Section: The CL 2 So Isomermentioning

confidence: 99%

The nature of the SO bond of chlorinated sulfur–oxygen compounds

Lindquist

2014

Theor Chem Acc

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Sulfur-oxygen chemistry encompasses a rich variety of chemical species and reactions. Sulfur-oxygen bonds can be quite short and strong, and historically, there has been disagreement as to the nature of the SO bond in sulfinyl groups. Early work invoked participation by the 3d orbitals of sulfur to explain the apparent double-bond character of sulfinyl bonds, but modern calculations have clearly established that sulfur 3d atomic orbitals do not participate as valence orbitals in hypervalent sulfur compounds. In prior work, we used generalized valence bond (GVB) theory to explain the features of the SO bond in the HSO/SOH structural isomers, and we extend that work here to the chlorinated analogs (ClSO/SOCl). We also use GVB theory to elucidate the nature of the bonding in Cl 2 SO and its higher energy structural isomer ClSOCl. We find that recoupled pair bonding, which we first introduced in our study of sulfur fluorides, is integral to describing the SO bond in all of these species. We also connect our analysis to the use of hyperconjugation to explain the backbonding in the p system in the sulfinyl halides.