A Masked Phosphinidene Trapped in a Fluxional NCN Pincer

摘要

The trapping of a phosphinidene (R-P) in an NCN pincer is presented. Stabilized phosphinidene 1 was characterized by P-31{H-1},H-1, and C-13{H-1} NMR spectroscopy, exhibiting an averaged C-2v symmetry in solution between -60 and 60 degrees C. In the solid state, the phosphinidene is co-ordinated by one adjacent N atom featuring a formal P-N bond (1.757(2) angstrom) to give a five-membered ring with some aromatic character, confirmed by DFT calculations (B3LYP-D3/6-311G**++) to be the ground-state structure. Equilibration of the two N ligands occurs rapidly in solution via a "bell-clapper"-type process through an associative symmetric transition state calculated to lie 4.0 kcal mol(-1) above the ground state.