Generation of spirotricyclic site-differentiated cyclotriphosphazenes: a solvent-free approach to multidentate N/O donor ligand systems.

Cyclotriphosphazene-based ligand systems are valuable materials to model the metal-binding event on the structurally and electronically related functionalized high molecular weight polyphosphazenes. We here report the facile synthesis of novel spirotricyclic cyclotriphosphazenes N(3)P(3)(MeNC(2)H(4)NMe)(2)L(2), N(3)P(3)(iPrNC(2)H(4)NiPr)(2)L(2), and N(3)P(3)(o-O(2)C(12)H(8))(2)L(2) that enables different substituents to be incorporated into the ligand system. This synthetic approach allows for control over the solubility and steric requirements of the exocyclic bidentate substituents, as well as the donor type and denticity of the coordination sites. A mononuclear lanthanum complex ([La(NO(3))(3)[N(3)P(3)(pzpy)(2)(MeNC(2)H(4)NMe)(2)]] (7)) and a series of dinuclear transition-metal complexes ([[ReCl(CO)(3)](2)[N(3)P(3)(pyNH)(2)(MeNC(2)H(4)NMe)(2)]] (4), [[FeI(2)](2)[N(3)P(3)(pyNH)(2)(MeNC(2)H(4)NMe)(2)]] (5), and [[PdCl(2)](2)[N(3)P(3)(pyNH)(2)(MeNC(2)H(4)NMe)(2)] (6)) have been prepared and structurally and spectroscopically characterized to explore the metal coordination environments supported by this class of ligands.