Pyrido-annulated 1,3,2-diazaphospholenium ions and P-bis(trimethylsilyl)amino substituted 1,3,2-diazaphospholenes were synthesised and characterised by spectroscopic methods and single-crystal X-ray diffraction studies. The distribution of bond distances provided evidence for π-electron delocalisation in the fused ring system. This hypothesis was confirmed by calculations of magnetic (NICS, nucleus independent chemical shift) and geometrical (Bird index, bond shortening index) aromaticity indexes which attest aromatic character of the five-membered rings in the cations that is lost upon introduction of a substituent at the phosphorus atom. Computation of isodesmic reaction energies suggest that the reclamation of aromatic stabilisation energies in the products facilitates reaction of P-amino-subsituted annulated diazaphospholenes under cleavage of the fused ring system.
通过光谱方法和单晶 X 射线衍射研究,合成了吡啶annulated 1,3,2-二氮磷烯离子和 P-双(三甲基硅基)氨基取代的 1,3,2-二氮磷烯。键距分布提供了π电子在融合环系统中脱位的证据。磁性(NICS,核独立化学位移)和几何(Bird 指数,键缩短指数)芳香指数的计算证实了这一假设。等位反应能的计算表明,产物中芳香稳定能的恢复有利于 P-氨基取代环状重氮磷烯在融合环系统裂解时的反应。