¹³C and ¹⁵N NMR shieldings of 1,2,4‐diazaphospholes in the solid state and in solution

Article type: Research Article

Authors: Claramunt, R.M. | López, C. | Schmidpeter, A. | Willhalm, A. | Elguero, J.^; | Alkorta, I.

Affiliations: Departamento de Química Orgánica y Biología, Facultad de Ciencias, UNED, Senda del Rey 9, E‐28006 Madrid, Spain | Department Chemie der Universität München, Butenandtstrasse 9, D‐81377 München, Germany | Instituto de Química Médica, CSIC, Juan de la Cierva 3, E‐28006 Madrid, Spain

Note: [] Corresponding author. E‐mail: [email protected].

Abstract: The solid state 13C and 15N CPMAS NMR spectra of 3,5‐di‐tert‐butyl‐1,2,4‐diazaphosphole 4 and 3,5‐diphenyl‐1,2,4‐diazaphosphole 5 have been recorded. The X‐ray structure of the first compound was already known (it is a cyclic dimer with localized N–H protons) while the structure of the second cannot be determined due to the difficulty to grow suitable single crystals. NMR results pointed out that 4 is a “classical” compound while 5 is probably a tetramer showing Intermolecular Solid‐State Proton Transfer (ISSPT). GIAO/ab initio calculations have been carried out to estimate the absolute 1H, 13C and 15N shieldings. The agreement with the experimental chemical shifts is good enough to assign the signals of carbons C‐3 and C‐5.

Journal: Spectroscopy, vol. 15, no. 1, pp. 27-32, 2001