Novel Reactions of Phosphaalkynes in the Coordination Sphere of tert‐Butylimido‐ vanadium(V) Complexes: A Simple Synthesis of 3‐Aza‐1,2,4,6‐tetraphosphaquadricyclanes and 1,3,5‐Triphosphabenzenes

A small variation in the vanadium reagent leads to a completely different product: The cyclooligomerization of phosphaalkynes 2 with tBuN=VCl3⋅DME (DME=1,2-dimethoxyethane) proceeds with incorporation of the imido fragment to give the azatetraphosphaquadricyclanes 1. In contrast, with the corresponding vanadium compound containing no Lewis base this fragment is not incorporated, and the 1,3,5-triphosphabenzenes 3 are obtained.