Hypervalent molecules, sulfuranes, and persulfuranes: review and studies related to the recent synthesis of the first persulfurane with all substituents carbon-linked

Abstract

In his classic 1969 review, Jeremy Musher introduced the term “hypervalent” to describe molecules composed of main group elements failing to satisfy the octet rule. Since that time, there has been much progress in the preparation and understanding of hypervalent molecules. Theoretical research from our group on sulfuranes and persulfuranes, two of the most important classes of hypervalent molecules, is reviewed in the first part of this Account. The immediate motivation for the new research reported here was the recent synthesis of the novel hypervalent persulfurane with all carbon ligands, cis-bis(2,2′-biphenylylene)dimethylpersulfurane (C12H8)2(CH3)2S, (Sato et al. J Am Chem Soc 128:6778, 2006), representing a landmark advance in main group chemistry. We have theoretically studied the synthesized compound, as well as its two trans forms, using density functional methods. Our theoretically optimized geometry for the cis structure is in good agreement with the experimental structure. Sulfur d orbital participation is relatively unimportant in the bonding. The trans-1 and trans-2 structures, which have not been observed experimentally, are predicted to be genuine minima, lying in energy above the cis structure by ~16 kcal/mol due to the strain of the geometric distortions. Two transition states for the relevant isomerizations have been located, and the energy barriers are discussed.