Dative versus electron-sharing bonding in N-oxides and phosphane oxides R3EO and relative energies of the R2EOR isomers (E = N, P; R = H, F, Cl, Me, Ph). A theoretical study.
Dative versus electron-sharing bonding in N-oxides and phosphane oxides R3EO and relative energies of the R2EOR isomers (E = N, P; R = H, F, Cl, Me, Ph). A theoretical study.
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DOI：
10.1039/c8cp00951a
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发表时间：
2018-05
期刊：
影响因子：
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通讯作者：
Tao Yang;D. Andrada;G. Frenking
中科院分区：
文献类型：
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作者：
Tao Yang;D. Andrada;G. Frenking
在CCSD（T）/def 2-TZVPP水平上用从头算方法和密度泛函理论BP 86和M06-2X泛函在def 2-TZVPP基组下对标题分子进行了量子化学计算.计算的能量表明，与R = F，Cl的N-氧化物R3 NO是较低的能量比胺异构体R2 NOR，但后者的形式是更稳定的比N-氧化物时，R = H，Me，Ph。相反，膦氧化物R3 PO总是更稳定的膦基异构体R2 NOR，除了与R = H的父系统，其中两个异构体是接近的能量。能量分解分析表明，对N-氧化物R3 NO中N-O键的最佳描述取决于取代基R的性质。卤素体系F3 NO和Cl 3 NO以及三苯基物种Ph 3 NO具有配位键R3 N →O，该配位键被R3 N <$O π反馈增强。在Ph_3NO中，π反馈贡献仅占总轨道相互作用ΔEorb的10%，而在F_3NO和Cl_3NO中，π反馈贡献占ΔEorb的22%。N-O键H3 NO和Me 3 NO可以用带电碎片R3 N +-O-之间的电子共享单键来更好地描述，这得到了适度的R3 N +<$O- π反馈的支持，其中包含13-16%的ΔEorb。相比之下，所有磷烷氧化物R3 PO最好用带电片段R3 P +-O-之间的电子共享单键来描述，这得到了贡献22-32% ΔEorb的R3 P +<$O- π反馈的显著支持。
Quantum chemical calculations using ab initio methods at the CCSD(T)/def2-TZVPP level and density functional theory using BP86 and M06-2X functionals in conjunction with def2-TZVPP basis sets have been carried out on the title molecules. The calculated energies suggest that the N-oxides R3NO with R = F, Cl are lower in energy than the amine isomers R2NOR, but the latter form is more stable than the N-oxides when R = H, Me, Ph. In contrast, the phosphane oxides R3PO are always more stable than the phosphanyl isomers R2NOR except for the parent system with R = H, where the two isomers are close in energy. The energy decomposition analysis suggests that the best description of the N-O bond in N-oxides R3NO depends on the nature of the substituent R. The halogen systems F3NO and Cl3NO and the triphenyl species Ph3NO possess dative bonds R3N→O, which are enhanced by R3N←O π backdonation. The contribution of the π backdonation is only 10% of the total orbital interactions ΔEorb in Ph3NO, but it amounts to ∼22% of ΔEorb in F3NO and Cl3NO. The N-O bonds H3NO and Me3NO are better described in terms of electron-sharing single bonds between charged fragments R3N+-O-, which are supported by modest R3N+←O- π backdonation that comprise 13-16% of ΔEorb. In contrast, all phosphane oxides R3PO are best depicted with electron-sharing single bonds between charged fragments R3P+-O-, which are significantly supported by R3P+←O- π backdonation contributing 22-32% of ΔEorb.