Base-Stabilized Phosphinidene Oxide, Imide and Sulfide

Oxidation of a base-stabilized phosphinidene (?(2)-NNP)P (12, NNP=phosphinoamidinate) with N2O afforded a labile phosphinidene oxide (?(2)-NNP)P=O (16) which was characterized by NMR spectroscopy. Further oxidation of 16 by N2O or reaction of 12 with two equivalents of pyridine oxide afforded the isolable dioxide (?(2)-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 (?(1)-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 N3SiMe3 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 (?(2)-NNP)P=S that has also been fully characterized.