Phosphorus-nitrogen heterocycles as ligands in organometallic chemistry

Abstract

λ³-Cyclodiphosphazanes of the type (RNPX)₂ (R=Ph, X=OC₆H₄-Me-p or OCH₂CF₃) react with Group 6 metal carbonyls to yield a variety of complexes depending on the geometrical disposition of the substituents on the phosphorus with respect to the P₂N₂ ring. Coordination occurs through the phosphorus centre(s) in the λ¹- or bridged bidentate(μ-) modes. On the other hand (amino)λ⁵-cyclotriphosphazenes afford Group 6 metal carbonyl complexes in which a phosphazene ring nitrogen atom is involved in coordination besides exocyclic nitrogen atoms. Complexes of Group 10 metal chlorides with cyclotriphosphazene ligands have also been synthesized. NMR spectroscopic and X-ray crystallographic studies have been carried out to elucidate the structures of the complexes.