Cycloaddition and electron transfer: On a synthetically useful aspect of pnictogen(I) reactivity

The behavior of several bi- or tri-dentate sp2-nitrogen-containing ligands with phosphorus(I) and arsenic(I) centers is investigated using computational and, in some cases, experimental methods. Whereas the chelation of putative PnI cations (Pn = P, As) by 1,4-diazabutadienes (DAB) generate stable, isolable phosphenium or arsenium cations that contain PnIII centers, the corresponding reactions of PnI cations with β-diketiminate (NACNAC) ligands do not yield similar planar heterocycles. The behaviors of the ligands 2,6-diiminopyridine and 2,2′-bipyridine fall between the extremes delimited by the DAB and NACNAC ligands. The results of computational investigations of potential products provide a framework to rationalize the chemistry observed.