Cyclodiphosphazane

Cyclodiphosphazanes are excellent ligand systems for metallosupramolecular chemistry.^[5] The cis-oriented lone pair on phosphorus in cyclodiphosphazane are projected away from each other, so chelation to metal center is not possible. This bridging coordination of cyclodiphosphazane allows formation of metallomacrocycles containing four rhodium and gold centers and metallopolymers CuX, AgX.^[6]

Chiral cyclodiphosphazanes have found use as ligands in asymmetric catalysis. Gade et al. employed them in enantioselective transition-metal mediated catalysis,^[7] while Goldfuss et al. employed di-amino substituted chiral variants in hydrogen bonding catalysis.^[8]

Cyclodiphosphazanes have also been found to have a high ability to bind anions via hydrogen bonding - specifically halides - in both their monomeric and macrocyclic forms. They are competitive to or better than comparable bifurcated anion binding structural motifs such as (thio)urea and squaramide.^{[9][10][11][12][13]}

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