Sulfur-Sulfur Lone Pair and Sulfur-Naphthalene Interactions in Naphtho[1, 8-b,c]-1,5-dithiocin

Richard S. Glass, Stephen W. Andruski, Jeffrey L. Broeker, Habib Firouzabadi, L. Kraig Steffen, George S. Wilson

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Abstract

Naphtho[1,8-b,c]-1,5-dithiocin (4), which has a unique geometry so constrained that the sulfur atoms are held close to one another and oriented such that their p orbitals are almost colinear and orthogonal to the naphthalene π-system, has been synthesized. Its crystal and molecular structure was determined by single-crystal X-ray analysis. It crystallizes in the orthorhombic space group Pbca with a = 8.140 (2) Å, b = 9.866 (1) Å, c = 28.302 (3) Å, and Z = 8. The structure was solved by direct methods. Full-matrix least-squares refinement led to a conventional R factor of 0.046 after several cycles of anisotropic refinement. For comparison purposes the crystal and molecular structure of the previously reported 1,8-bis-(methylthio)naphthalene (5) was also determined by X-ray techniques. Semiempirical molecular orbital methods (MNDO and AM1) were used to analyze the five highest occupied molecular orbitals in l,8-bis(methylthio)naphthalene as a function of the C(1)-S and C(8)-S torsion angles and to analyze the molecular orbitals of compound 4. Of particular interest is the result that the energy of the highest occupied molecular orbital in 1,8-bis(methylthio)naphthalene is nearly independent of the C-S torsion angle and that the lowest ionization potential for 4 is predicted to be 7.75 eV and its lone pair-lone pair splitting due to transannular S-S interaction is 1.6-2.0 eV. The computations were correlated with the experimentally measured He I and He II photoelectron spectra of 4 and the AM1 method provided reasonable agreement with the experimental data. The electrochemical oxidation of 4 and 5 in acetonitrile was studied by cyclic voltammetry. They undergo irreversible oxidation with peak potentials of 0.70 and 0.47 V, respectively, versus a Ag/0.1 M AgNO3 in acetonitrile reference electrode. Controlled-potential electrolysis of 4 gives the corresponding sulfoxide (12), which is consistent with removal of an electron from the highest occupied molecular orbital which is sulfur lone pair in character.

Original languageEnglish (US)
Pages (from-to)4036-4045
Number of pages10
JournalJournal of the American Chemical Society
Volume111
Issue number11
DOIs
StatePublished - May 1989

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ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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