1,5-Diaza-3,7-diphosphacyclooctanes

They are air-sensitive white solids that are soluble in organic solvents.

The catalytic mechanism involves the interaction of substrate with the amines in the second coordination sphere.

Typical nickel complexes contain two such ligands are give the formula [Ni(PR2NR'2)2]2+.

Cationic complexes of these P2N2 and related ligands often exhibit enhanced reactivity toward H2.

They are prepared by condensation of 1,2-bis(phenylphosphino)ethane, formaldehyde, and a primary amine.

P2N2 ligand structure
Conformation of chelate rings in P2N2-M and P2N-M complexes