Cyclodiphosphazanes with functionalities: Synthesis, reactivity and transition metal chemistry

The saturated, four-membered rings of the type [XP(μ-NR)]2 containing alternating phosphorus(III) and nitrogen atoms are known as cyclodiphosphazanes or diazadiphosphetidines. The current interest in these well-known heterocycles is due to their catalytic and biological applications besides their excellent synthetic utility as scaffolds to design interesting macrocycles with or without involving main group or transition metals. Although the rigid and nearly-planar neutral P2N2 rings resemble [Cu(μ-X)]2 (X = Cl, Br or I) rhombic units ([Cu(μ-X)]2 are known for giving a variety of structures with suitable ligands), their utility in designing the high-nuclearity clusters, cages or coordination polymers is scarce. In this context, we fine tuned the coordinating ability of these ligands by incorporating pendant hemi-labile functionalities on phosphorus centers which resulted in the isolation of several interesting molecules. The details are described.