Synthesis of azadiphosphiridine complexes. Theoretical studies on ring formation, the P-to-P' metal shift and the resulting nitrogen geometry

A set of azadiphosphiridine complexes 3a and 4b,c were synthesized in high selectivity using N-H and P-H deprotonation as key steps and RPCl₂ as substrates (R = NⁱPr₂ (a), -^tBu (b), Ph (c)). While complex 3a (P-NⁱPr₂) retained the P-W linkage of the starting material W(CO)₅{Ph₃CP(H)NH}, complexes 4b (P-^tBu) and 4c (P-Ph) revealed that a P-to-P' haptotropic shift of the W(CO)₅ group has occurred. Remarkably, complex 3a, bearing an unligated P-NⁱPr₂ unit, displays a planar ring N geometry while 4b,c showed a pyramidal geometry of the ring nitrogen atom. Theoretical studies on the ring formation including the P-to-P' haptotropic metal shift and the factors influencing the ring nitrogen geometry are reported.