Relativistic DFT calculation of 119Sn chemical shifts and coupling constants in tin compounds
Relativistic DFT calculation of 119Sn chemical shifts and coupling constants in tin compounds
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DOI：
10.1021/ct050173k
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发表时间：
2006-01-01
影响因子：
5.5
通讯作者：
Saielli, G
中科院分区：
文献类型：
--
作者：
Bagno, A;Casella, G;Saielli, G
本文采用密度泛函理论（DFT）方法和斯莱特全电子基组计算了Sn-119在锡烷、四甲基锡烷、甲基卤化锡Me_（4-n）SnXn（X = Cl，Br，l; n = 1-3）、卤化锡和一些锡基阳离子中的核屏蔽常数和自旋-自旋耦合常数，并采用零级正则近似（ZORA）方法计算了自旋-轨道耦合的相对论效应.计算的Sn-119化学位移一般与实验值，除了当几个重卤素原子，特别是碘，结合到锡。在这种情况下，计算的化学位移几乎是恒定的标量（自旋自由）ZORA水平;只有在自旋轨道水平是一个很好的相关性，这适用于所有的化合物检查，达到。一个显著的“重原子效应”，类似于对类似的烷基卤化物所观察到的，是显而易见的。假定的甲锡烷基阳离子（SnH 3+）的化学位移也进行了检查，并得出结论，在超强酸中得到的物种的光谱是不一致的一个简单的SnH 3+结构;强协调，甚至弱亲核试剂，如FSO 3 H导致一个非常令人满意的协议。与此相反，计算的Sn-119化学位移的均三甲苯甲锡烷基阳离子是在非常好的协议与实验值。Sn-119和卤素原子核之间的耦合常数也被很好地模拟了（考虑到实验值的不确定性）;相对论自旋轨道效应也很明显。平均而言，与C-13和H-1的耦合也落在相同的相关线上，但个别值显示出与预期单位斜率的显著偏差。
The nuclear shielding and spin-spin coupling constants of Sn-119 in stannane, tetramethylstannane, methyltin halides Me4-nSnXn (X = Cl, Br, l; n = 1-3), tin halides, and some stannyl cations have been investigated computationally by DFT methods and Slater all-electron basis sets, including relativistic effects by means of the zeroth order regular approximation (ZORA) method up to spin-orbit coupling. Calculated Sn-119 chemical shifts generally correlate well with experimental values, except when several heavy halogen atoms, especially iodine, are bound to tin. In such cases, calculated chemical shifts are almost constant at the scalar (spin-free) ZORA level; only at the spin-orbit level is a good correlation, which holds for all compounds examined, attained. A remarkable '' heavy-atom effect '', analogous to that observed for analogous alkyl halides, is evident. The chemical shift of the putative stannyl cation (SnH3+) has also been examined, and it is concluded that the spectrum of the species obtained in superacids is inconsistent with a simple SnH3+ structure; strong coordination to even weak nucleophiles such as FSO3H leads to a very satisfactory agreement. On the contrary, the calculated Sn-119 chemical shift of the trimesitylstannyl cation is in very good agreement with the experimental value. Coupling constants between Sn-119 and halogen nuclei are also well-modeled in general (taking into account the large uncertainties in the experimental values); relativistic spin-orbit effects are again quite evident. Couplings to C-13 and H-1 also fall, on the average, on the same correlation line, but individual values show a significant deviation from the expected unit slope.