Fragmentation of an N-Substituted One-Coordinate Phosphorus (Phosphaalkyne): Plausible Generation of Monovalent Phosphorus Species

A new one-step synthesis of a stable nitrogen-substituted phosphaalkyne (5) was developed, by the condensation of CsF (2), tris(trimethylsilyl)phosphine (3), and supermesityl isocyanate (4). Compound 5 has the longest terminal CP bond (1.617 Å) of any phosphaalkyne. Due to electron delocalization on the terminal phosphorus atom in 5, fragmentation to a monovalent phosphorus species (CsP (9)) and supermesityl isonitrile (8) is plausible. Isonitrile (8) was isolated in pure form. CsP (9) was trapped as a tricesium pentaphosphorus compound (10) and also as cesium [1,2,4]triphospholide (13).