Abstract
Properties and ring opening reactions are investigated for azaphosphirane and its P-phenyl and W(CO) 5 complex using density functional theory (B3LYP). Azaphosphirane has a relatively small N-inversion barrier of 10.8 kcal mol −1 and a high 56.8 kcal mol −1 ‘turnstile’ P-inversion barrier. Its strain energy is 26.5 kcal mol −1 at G3(MP2). The PC bond is the weakest bond. Only 27.4 kcal mol −1 is needed to break it, which is half that needed for both the CN and PN bonds. This PC ring opening to the P, N-ylide is endothermic by 8.5 kcal mol −1. P-phenyl substitution has little effect neither on the geometries nor on the energy of the ring opening. Complexation by W(CO) 5 leads to a tighter ring but the energy for breaking the PC bond still requires 27.8 kcal mol −1. The resulting P, N-ylide is only 3.9 kcal mol −1 less stable than azaphosphirane. Cleaving either the CN or PN bond remain much more demanding processes. The calculations suggest that the reactivity of azaphosphirane may well have its origin in the readily accessible P, N-ylide. Its influence on the reaction of phosphinidenes with imines is discussed.
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