N-Aryl-S,S-dimethyliminosulfuranes. Structure, Dipole Moments, and Extent of Double Bonding

The crystal structure of N-(p-nitrophenyl)-S,S-dimethyliminosulfurane is reported. The short N-S bond (1.651 Å) implies a substantial amount of double bonding and bond length distortions in the aromatic ring suggest extensive resonance involvement of the p-nitrophenyl moiety. The dipole moments of five para-substituted N-aryl-S,S-dimethyliminosulfuranes (para substituents: F, Cl, Br, CN, NO2) imply 45–58% ionic character in the N-S bond, least for p-F, most for P-NO2. It is concluded that the two canonic forms Ar-N--S+Me2 ⟷ Ar-N=SMe2 contribute about equally to the resonance hybrid with the dipolar form predominating only when there are strongly electron- withdrawing substituents at the para position in the benzene ring. © 1976, American Chemical Society. All rights reserved.

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Author Andrew T. McPhail Chemistry