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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Nuclear Magnetic Shielding of Monoboranes: Calculation and Assessment of B-11 NMR Chemical Shifts in Planar BX3 and in Tetrahedral [BX4](-) Systems
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Nuclear Magnetic Shielding of Monoboranes: Calculation and Assessment of B-11 NMR Chemical Shifts in Planar BX3 and in Tetrahedral [BX4](-) Systems

机译：单卤素的核磁屏蔽：平面BX3和四面体[BX4]（ - ）系统中B-11 NMR化学位移的计算与评估

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摘要

B-11 NMR chemical shifts of tricoordinated BX3 and tetracoordinated BX4- compounds (X = H, CH3, F, Cl, Br, I, OH, SH, NH2, and CH=CH2) were computed, and the shielding tensors were explored not only within the non relativistic GIAO approach but also by application of both relativistic ZORA computations including spin orbit coupling as well as scalar nonrelativistic ZORA computations (BP86 level of density functional theory). The contributions of the spin orbit coupling to the overall shieldings are decisive for X = Br and I in both series. No relationship was found between the 2p orbital occupancies or 1/Delta E (difference between LUMO and suitably occupied MO that can be coupled with LUMO) with the shielding tensors (or their principal values) in the BX3 series. However, a multidimensional statistical approach known as factor analysis (frequently used in chemometrics) revealed that three factors account for 92% of the cumulative proportion of total variance. The main components of the first factor are occupancies in the 2p(x) and 2p(y)), orbitals and 1/Delta E; the second factor is mainly the occupancy in the 2p(z) orbital and the inductive substituent parameters by Taft. Finally, the third factor consists exclusively (98.4%) of the electrostatic potential (V-max), which is directly related to the so-called pi-hole magnitudes.
机译：计算三合化Bx3和四元化Bx4-化合物的B-11 NMR化学位移（X = H，CH3，F，Cl，Br，I，OH，SH，NH 2和CH = CH2），探索屏蔽张量只有在非相对论的助怒方法中，还通过应用相对论的Zora计算，包括自旋轨道耦合以及标量非筛选佐拉计算（BP86密度函数理论）。旋转轨道耦合到整体屏蔽的贡献对于X = BR和I系列中的X = BR耦合是决定性的。 2P轨道占用或1 /ΔE之间没有任何关系（Lumo和合适的Mo之间的差异，可以与Lumo耦合的悬垂的Mo），并在BX3系列中屏蔽张量（或其主值）。然而，称为因子分析（经常用于化学计量学）的多维统计方法揭示了三种因素占总方差累积比例的92％。第一因素的主要成分在2P（x）和2p（y）中占用），轨道和1 / delta e;第二个因素主要是2P（Z）轨道和塔夫诱导取代基参数的占用率。最后，第三因素专门（98.4％）的静电电位（v-max）组成，其与所谓的Pi孔幅度直接相关。

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