A novel N,P,C cage complex formed by rearrangement of a tricyclic phosphirane complex: on the importance of non-covalent interactions.

The reaction of Li/Cl P-CPh3 phosphinidenoid tungsten(0) complex 2 with dimethylcyanamide afforded tricyclic phosphirane complex 4, an unprecedented rearrangement of which led to the novel N,P,C cage complex 6. On the basis of DFT calculations, formation and intramolecular [3+2] cycloaddition of the transient nitrilium phosphane ylide complex 3 to a phenyl ring of the triphenylmethyl substituent to give 4 is proposed. Furthermore, theoretical evidence for terminal N-amidinophosphinidene complex 7, formed by [2+1] cycloelimination from 4, is provided, and the role of the electronic structure and non-covalent interactions of intermediate 7 discussed.