Insights into the chemistry of sulfur-containing molecules

recoupled pair bonding;hypervalent molecules;Generalized Valence Bond (GVB) Theory

Lindquist, Beth

关键词: recoupled pair bonding;    hypervalent molecules;    Generalized Valence Bond (GVB) Theory;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/49568/Beth_Lindquist.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

In this dissertation, we utilize generalized valence bond (GVB) theory and the recoupled pair bonding model in order to understand the chemical bonding in a variety of sulfur-containing molecules. We use the resulting insights to rationalize experimental and computational results as well as to make predictions about the structures, energetics and other properties of molecules. Prior work in our group found that a new type of three-electron interaction—the recoupled pair bond—provides the basis for bonding in hypervalent species, i.e., species that form more bonds than would be predicted from the nominal valence of the central atom. However, this new type of bond has implications that reach well beyond hypervalent species. In this work, we explore a variety of molecules and show that the ability of elements beyond the first row to form recoupled pair bonds explains many observed anomalies. We investigated many species where recoupled pair bonds are integral to a complete description of bonding. For instance, we found that the axial bonds of FSSF3 (the product of SF2 dimerization) are a recoupled pair bond dyad, and this allowed us to explain the lack of an inverse relationship between S−F bond length and strength for this molecule, one of several counter-intuitive properties of FSSF3.We also made a significant extension of the recoupled pair bonding model by showing that recoupled pair bonds are formed in π systems as well as in σ systems. In particular, we showed that the ground (3Σ−) state of SO is bound by a polar covalent σ bond and a recoupled pair π bond. We explored the implications of this new bonding motif for various sulfur-oxygen compounds, including (but not limited to) the HSO and SOH isomers, SO2, and Cl2SO. We conclude that GVB theory in conjunction with the recoupled pair bonding model is a valuable tool for the examination of bonding in a broad range of molecules, and this theoretical framework has allowed us to gain unique insights into their structures and chemical properties.