Investigation of Phosphazene Superbase Interactions\nwith [PCl<sub>2</sub>N]<sub>3</sub>

In this study, the reaction between\nphosphazene superbases and\na chlorophosphazene trimer ([PCl<sub>2</sub>N]<sub>3</sub>) has been\ninvestigated. In this room temperature reaction, the phosphazene superbase\n(Me<sub>2</sub>N)<sub>3</sub>PN(Me<sub>2</sub>N)<sub>2</sub>PNEt,\ncommonly known as P<sub>2</sub>Et, was shown to behave as a nucleophile,\ndisplacing one of the chlorides from [PCl<sub>2</sub>N]<sub>3</sub> and producing the tadpole-like structure <b>1</b>. The reaction\ndescribed herein is one of the few instances of a phosphazene superbase\nbehaving as a nucleophile rather than a Brønsted base. Once formed,\nthis structure contains contrasting reactivity, containing a weakly\nbasic phosphazene head while maintaining a highly basic phosphazene\ntail of the tadpole. The mechanism of the reaction was explored by\ninvestigating the potential energy surface through density functional\ntheory calculations at the B3LYP/6-311+G(d,p) level of quantum mechanical\ntheory. It was determined that the reaction of P<sub>2</sub>Et with\n[PCl<sub>2</sub>N]<sub>3</sub> followed a stepwise process beginning\nwith the substitution of P<sub>2</sub>Et onto [PCl<sub>2</sub>N]<sub>3</sub> with the concurrent loss of chloride. Subsequently, the chloride\nattacks the ethyl group of the P<sub>2</sub>Et moiety, and ethyl chloride\nis released, producing <b>1</b>. Compound <b>1</b> was\nfurther characterized via <sup>31</sup>P NMR spectroscopy, mass spectrometry,\nand X-ray crystallography.