Structural Features of Tetraazathiapentalenes Fused with Pyrimidine and/or Pyridine Rings. Experimental Evaluation of the Nature of Hypervalent N−S−N Bond by Restricted Internal Rotation of the Pyrimidine Ring
dimethylated (17) 10-S-3 sulfuranes, derivatives of tetraazathiapentalenes fused with pyrimidine and/or pyridine ring, were prepared. These molecules are planar, and bond energies of the hypervalent N−S−N bond were evaluated by the temperature dependent restrictedrotation of the pyrimidine ring caused by cleavage of one of the S−N bonds. The bond length is longer, and the energy is lower for the S−N bond
制备了一系列中性 (8-10)、单甲基化 (12-14) 和二甲基化 (17) 10-S-3 硫烷,四氮杂硫戊烯与嘧啶和/或吡啶环稠合的衍生物。这些分子是平面的,高价 NS-N 键的键能通过由 SN 键之一断裂引起的嘧啶环的温度依赖性限制旋转来评估。与更多吸电子杂环稠合的 SN 键的键长更长,能量更低。
Restricted rotation of pyrimidine ring in symmetrical 10-S-3 sulfuranes: Evaluation of hypervalent NSN bond energy
Symmetrical 10-S-3 sulfuranes (-) fused with two pyrimidine rings and their unsymmetrically substituted ones (,) were synthesized by oxidation of the corresponding thioureas. Substituent effect on the kinetic data of the restrictedrotation was explained in terms of the balance of electron-withdrawing ability of the ligand in the NSN hypervalent bond.