Base-Stabilized Phosphinidene Oxide, Imide and Sulfide

Oxidation of a base-stabilized phosphinidene (κ² -NNP)P (12, NNP=phosphinoamidinate) with N₂ O afforded a labile phosphinidene oxide (κ² -NNP)P=O (16) which was characterized by NMR spectroscopy. Further oxidation of 16 by N₂ O or reaction of 12 with two equivalents of pyridine oxide afforded the isolable dioxide (κ² -NNP)PO₂ which was characterized by NMR and SC XRD. Trapping of 16 with tolyl isocyanate resulted in P=O/N=C metathesis, eventually affording a urea-ligated phosphine (κ¹ -NNP)P(NTol)₂ C=O (17) The mechanism of this reaction was elucidated by DFT calculations. Reactions of phosphinidene 12 with azides generated transient imines (NNP)P=NR, which in the case of R=Tol underwent cycloaddition with tolyl Isocyanate to afford the urea product 17, and in the case of R=SiMe₃ reacts with N₃ SiMe₃ via the addition of N-Si across the P=N bond affording, after the extrusion of dinitrogen, a P,N-heterocyclic compound. Both products of the reactions with azides have been fully characterized, both in solution and the solid-state. Finally, reaction of phosphinidene 12 with one equivalent of sulfur resulted in the isolation of the base-stabilized phosphinidene sulfide (κ² -NNP)P=S that has also been fully characterized.