Design of Polycyclic Molecules of Group 15 Elements and Pentagon Stability

结果表明，在由15族元素组成的单环分子（XH）n（XN，P，As）中，五元环是最稳定的，15族元素中原子的孤对电子以环状方式离域，因为孤对电子的n轨道和邻位X-X键的σ^* 轨道的相位是连续的.键模型分析表明，n-σ^* 相互作用对X=N没有显著的稳定作用，但对X=P和As有显著的稳定作用。当X=N时，五元环比六元环的张力更大。令人惊讶的是，五元环（X=P和As）具有负应变能，并且比六元环应变小。根据五边形稳定性，我们设计了低应变的P和As多环分子，证明了铝阴离子、卡宾、硅烯和锗烯等化学物种的五边形稳定性，其中环戊烷的一个碳原子被相应的原子取代，证明了化学反应的过渡态的五边形稳定性。环戊烷脱质子反应的活化能为4.25 kcal/mol，低于环己烷脱质子反应的活化能4.52 kcal/mol。

We showed that the five-membered ring is the most stable of the monocylic molecules (XH)n (XN,P,As) composed of the 15 group elements and designed mono-and polycyclic molecules with low strains.A lone pair of an atom in the 15 group delocalize in a cyclic manner since the phase of the n-orbital for the lone pairs and the σ^*-orbitals of the vicinal X-X bonds is continuous. The bond model analysis showed that n-σ^* interaction does not contribute to significant stabiizization for X=N but for X=P and As. The five membered ring is more strained than the six-membered ring for X=N. To our surprise, the five-membered rings (X=P and As) have negative strain energies, and are less strained than the six-membered rings. According to the pentagon stability, we designed polycycic molecules of P and As with low strains.We showed the pentagon stability of the chemical species, aluminum anion, carbene, silylene, and germylene, where an carbon atom of cyclopentane is replaced by the corresponding atom.The pentagon stability is shown for the transition states of chemical reactions. For example, the activation energy (4.25) kcal/mol) of the deprotonation from cyclopentane is lower than that (4.52 kcal/mol) from cyclohexane.