NMR Chemical Shift Calculation

Arenium cations were the first carbocations investigated by GIAO-MP2 NMR chemical shift calculations. 

NMR chemical shift calculations were performed for the B3LYP/6-31G(d) optimized anti and syn isomeric structures of the analogous l-p-anisyl-2-SiH3 substituted... 

The cyclobutenyl cation 92 is one of the first examples demonstrating that electron correlation is required both for geometry optimization and NMR chemical shift calculations.14 The IGLO/6-31G(d,p) calculated 13C NMR chemical shifts of the planar form of a homotropylium cation 94 clearly deviate from the experimental values (mean deviation A = 45.6 ppm) alternating in the seven-membered ring between 122 and 194 ppm, whereas those of the non-planar structure for the homotropylium cation 93 are in good agreement with experiment (mean deviation A = 6.2 ppm).108... 

Figure 5. Experimental and calculated (15) NMR chemical shifts in alkali iodides. NMR chemical shifts calculated from wave function given by Equation 8 and corrected for shift of reference sample with respect to free I ion, —9 X 10 ...

Accurate NMR chemical shift calculations for silicon compounds are available since the early 1990 s and these computations played a decisive role in the identification and characterization of silylium ions in the condensed phase. This issue has... 

A number of terms complicate the accurate calculation of Sn NMR chemical shifts, not least the possible importance of spin-orbit coupling and relativistic effects and Sn NMR chemical shift calculations became only feasible quite recently." " Therefore, the early estimates for the Sn NMR chemical shift for a trivalent... 

Until the year 2002 no experimental data existed on the structures of unperturbed RsE" cations, the exact analogues of the carbenium ions. Computational data combined with NMR chemical shift calculations, which could be compared to experiment, were the only source of reliable structural information for silylium... 

K. Wolinski, J. F. Hinton and P. Pulay, Efficient implementation of the gauge-independent atomic orbital method for NMR chemical-shift calculations. J. Am. Chem. Soc., 1990, 112,8251-8260. 

The internally stabilized silyl cation (36), formed by hydride transfer as shown, has a 2-silanorbomyl cation structure, and is not coordinated to die solvent or the counterion.78 NMR chemical shifts calculated on the basis of die bridged structure shown are in agreement with the experimental values. The autiiors describe it as free but internally re-stabilized .78 The silicon-stabilized oxonium ion (37) shows considerable stereoselectivity in its reactions (38) is the preferred product isomer by a 92 8 ratio, and (39) by 98 2.79... 

Waller MP, Biihl M, Geethalakshmi KR, Wang D, Thiel W (2007) 51V NMR Chemical Shifts Calculated from QM/MM Models of Vanadium Chloroperoxidase. Chem Eur J 13 4723... 

The structure of isolated R3M+ cations in the gas phase was the subject of several computational studies. Significant difficulties are associated with calculations for molecules containing the heavier elements, particularly Sn and Pb. NMR chemical shift calculations require consideration of relativistic effects (spin-orbit coupling). A discussion of these difficulties and of effective core potentials developed for these calculations is beyond the scope of this review. 

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