Phosphirenylium ions

It is the only example of a free, persistent phosphirenylium ion, and also, only one stable transition-metal complex of this species was published [78,79]. Quantum chemical calculations [80,81] indicated that in the halogeno-phosphirenes the P-X bonds already possesses a high ionic character and can be described as interactions between phosphirenylium and halide ions. The aromatic character of the phosphirenylium ion was shown to be based on a three-centre two-electron bond of 7i-type and the resonance energy was assessed by calculation to 38 kcal/mol. Before the generation of 32, substituted phosphirenylium ions were... 

Laali and coworkers132 investigated the reaction of the gaseous 2-f-butyl-3-phenyl-phosphirenylium ion (a 2jr-Huckel phosphirenylium ion) with aniline and other nucleophiles and dienes via MS" experiments. In ion/molecule reactions, the ion reacts readily with aniline to form an azonium ion via nucleophilic attack at phosphorus by the amino group, as suggested by calculations and MS3 experiments. 

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