First Calculations of 15N−15N J Values and New Calculations of Chemical Shifts for High Nitrogen Systems: A Comment on the Long Search for HN5 and Its Pentazole Anion
- 9 March 2009
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Physical Chemistry A
- Vol. 113 (13), 3197-3201
- https://doi.org/10.1021/jp809267y
Abstract
In the potential solution observation of the long-sought-after pentazole anion (N5−), the principal experimental tool used for detection is NMR. However, in two experiments, very different conclusions were reached. To assist in the interpretation, we report predictive level coupled-cluster results for the spin−spin coupling constants and chemical shifts for all of the key species, which include NO3−, N5−, HN5, N3−, and MeOC6H5N3. In the case of the shifts, an empirical estimate based on the molecule polarity enables comparison of gas-phase and observed values with expected error bars of ∼ ±10 ppm. For the scalar couplings, the evidence is that the solution effects are modest, enabling the gas-phase values (with error bars are ∼ ±5 Hz) to be accurate. The latter supports the observation of centrally 15N labeled N3− in the cerium(IV) ammonium nitrate (CAN) solution which could only occur if the pentazole anion had been created in the experiment, yet with too short a lifetime to be observed in NMR.Keywords
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