Investigation of Phosphazene Superbase Interactions with [PCl₂N]₃

In this study, the reaction between phosphazene superbases and a chlorophosphazene trimer ([PCl₂N]₃) has been investigated. In this room temperature reaction, the phosphazene superbase (Me₂N)₃PN(Me₂N)₂P═NEt, commonly known as P₂Et, was shown to behave as a nucleophile, displacing one of the chlorides from [PCl₂N]₃ and producing the tadpole-like structure <b>1</b>. The reaction described herein is one of the few instances of a phosphazene superbase behaving as a nucleophile rather than a Brønsted base. Once formed, this structure contains contrasting reactivity, containing a weakly basic phosphazene head while maintaining a highly basic phosphazene tail of the tadpole. The mechanism of the reaction was explored by investigating the potential energy surface through density functional theory calculations at the B3LYP/6-311+G(d,p) level of quantum mechanical theory. It was determined that the reaction of P₂Et with [PCl₂N]₃ followed a stepwise process beginning with the substitution of P₂Et onto [PCl₂N]₃ with the concurrent loss of chloride. Subsequently, the chloride attacks the ethyl group of the P₂Et moiety, and ethyl chloride is released, producing <b>1</b>. Compound <b>1</b> was further characterized via ³¹P NMR spectroscopy, mass spectrometry, and X-ray crystallography.