Chlorine/oxygen transfer reactions of [PCl₂N]₃ using oxygenated Lewis bases as a possible route to [PON]₃

GRAPHICAL ABSTRACT

ABSTRACT

The reactions of [PCl₂N]₃ with oxygen containing Lewis bases (O˭E) such as hexamethylphosphoramide (HMPA) and triethylphosphine oxide result in Cl/O exchange. The reactions occur via a two-step process which involves (1) formation of an intermediate salt [P₃N₃Cl₅O]^-[E-Cl]⁺ and (2) attack by more O˭E to form P₃N₃Cl₄O-O˭E and [E-Cl]⁺[Cl]⁻. In addition to spectral characterizations, both phosphazene products of the HMPA reactions have been characterized by X-ray crystallography. As shown by reaction chemistry and the Gutmann–Beckett Lewis acidity scale, the P˭O of the phosphazene ring in P₃N₃Cl₄O-O˭E has a strong Lewis acid character. We also discuss attempts to use other O˭E and more vigorous reaction conditions with the goal of preparing [PON]₃ or its base-stabilized adducts. Such molecules could be precursors to novel PNO materials.

KEYWORDS:

• Phosphazene
• Cl/O exchange
• ³¹P NMR

Acknowledgments

The authors thank the Goodyear Corporation for donation of an NMR instrument used in this work.

Funding

The authors thank Israel Chemical Limited and OMNOVA Foundation for support. The authors also thank the National Science Foundation and the Ohio Board of Regents for funds used to purchase the NMR (CHE-9977144), MS (DMR-0821313) and the X-ray diffractometer (CHE-0116041) instruments used in this work.