Phosphorus-31 solid-state nuclear magnetic resonance spectroscopy, individual gauge for localized orbitals calculations and crystal structures of dithiadiphosphetanes [RSP(S)S]2(R = alkyl or aryl)

Abstract

For a number of dithiadiphosphetanes [RSP(S)S]₂1 the ³¹P nuclear magnetic shielding tensor has been investigated. Phosphorus chemical shift δ_iso and principal values of the shielding tensor σ_ii have been calculated from CP MAS (cross polarization magic angle spinning) spectra. The orientation of the principal axes of the shielding tensor with respect to the dipolar coupling vector has been determined from the static powder spectra of [MeSP(S)S]₂1a. Ab initio calculations of the ³¹P shielding tensor have been performed using the individual gauge for localized orbitals method. The calculated data correspond well with the experimental. The most shielded component (the corresponding axis is 3) is approximately perpendicular to the PS₂P ring plane {angle P ⋯ P–3 ≈ 107° for [MeSP(S)S]₂}. Axis 2 is perpendicular to the SP–S(3) plane. Since axis 1 is perpendicular to axes 2 and 3 it intersects the S–P–S angle of both the terminal S atoms. The crystal structures of compounds [C₆H₁₁SP(S)S]₂1c and [PhCH₂SP(S)S]₂1d have been determined. Both compounds crystallize in the monoclinic space group no. 14 (1cP2₁/a, 1dP2₁/n). The unit cell of 1c contains two crystallographically independent molecules.