The bonding situation in 1,3,2‐diazaphospholene derivatives as studied by solid‐state NMR spectroscopy

Abstract

AbstractThe 31P chemical shift (CS) tensors of the 1,3,2‐diazaphospholenium cation 1 and the P‐chloro‐1,3,2‐diazaphospholenes 2 and 3 and the 31P and 19F CS tensors of the P‐fluoro‐1,3,2‐diazaphospholene 4 were characterized by solid‐state 31P and 19F NMR studies and quantum chemical model calculations. The computed orientation of the principal axes system of the 31P and 19F CS tensors in the P‐fluoro compound was found to be in good agreement with experimentally derived values obtained from evaluation of P–F dipolar interactions. A comparison of the trends in the chemical shifts of 1–4 with further available literature data confirms that the unique high shielding of δ11 in the cation 1 can be related to the effective π‐conjugation in the five‐membered heterocycle, and that a further systematic decrease in δ11 for the P‐halogen derivatives 2–4 is attributable to the increased perturbation of the π‐electron distribution by interaction with the halide donor. Copyright © 2002 John Wiley & Sons, Ltd.