Solid State15N NMR and Theoretical Studies of Primary and Secondary Geometric H/D Isotope Effects on Low-Barrier NHN−Hydrogen Bonds
| Autor: | Hans-Heinrich Limbach, Martin Wehlan, ‡ Wolf-Peter Fehlhammer, Rudolf Janoschek, Hans Benedict, and Nicolai S. Golubev |
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| Rok vydání: | 1998 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 120:2939-2950 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja9719790 |
| Popis: | Using a combination of high resolution and dipolar solid state 15N NMR we have determined H/D isotope effects on the nitrogen-hydron (L = H, D) distances and 15N chemical shielding tensors of strongly hydrogen bonded bisisocyanide salts of the type [(CO)5Cr−C⋮N···L···N⋮C−Cr(CO)5]- X+, where X+ = AsPh4+ (2) and X+ = NPr4+ (3). These compounds have been modeled theoretically by the linear system [C⋮N···L···N⋮C]-Li+ (1). The crystal field acting on the anion was generated by a variety of fixed C···Li distances. For the calculation of dynamical corrections of geometries and NMR chemical shifts, an iterative procedure based on the crude adiabatic approximation was employed, consisting of (i) ab initio calculation of the energy hypersurface at the MP2/6-31+G(d,p) level, (ii) solution of the Schrodinger equation for the anharmonic collinear hydron motion, and (iii) NMR chemical shift calculations using the IGLO-method. The two hydrogen bond distances r1 ≡ N···L and r2 ≡ L···N are found to change in a correlated ... |
| Databáze: | OpenAIRE |
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