A Rare Example of a Rearrangement Involving Four Structural Isomers: α ‐Phosphinonitrile/ C ‐Phosphinoketenimine/1‐Aza‐4‐phosphabutadiene/ 1,2‐Dihydro‐1,2‐azaphosphete

The stable compound [bis(dicyclohexylamino)phosphino](trimethylsilyl)carbene ( 1 ) reacts with dimethyl cyanamide to afford the original 1,2‐dihydro‐1,2‐azaphosphete 4 a (51 % yield). The surprising formation of this heterocycle involves the transient formation of a nitrile, a keteneimine, and a 1‐aza‐4 λ 3 ‐phosphabutadiene derivative. By using substituent effects and different synthetic routes, all of these structural isomers have been isolated.