Copper(ii) chloride complexes with multimodal ligands based on the cyclotriphosphazene platform

Abstract

The reaction of hexakis(2-pyridyloxy)cyclotriphosphazene (L) and hexakis(4-methyl-2-pyridyloxy)cyclotriphosphazene (MeL) with copper(II) chloride afford the complexes [CuLCl₂], [(CuCl₂)₂(MeL)], [CuLCl]PF₆ and [Cu(MeL)Cl]PF₆. The single-crystal X-ray structure of [CuLCl₂] shows the copper ion to be in a square based pyramidal distorted trigonal bipyramidal (SBPDTBP) environment (τ = 0.47) with L acting as a κ³N donor, coordinating via the nitrogen atoms from two non-geminal pyridyloxy pendant arms, a nitrogen atom in the phosphazene ring and two chloride ions. In the dimetallic complex, [(CuCl₂)₂(MeL)], the geometry about both (symmetry related) copper(II) centres is also SBPDTBP (τ = 0.57) with a ‘N₃Cl₂’ donor set. In the monocation of [CuLCl]PF₆, L acts as a κ⁵N donor, bonding to the copper(II) centre through the nitrogen atoms of four pyridyloxy pendant arms, a phosphazene ring nitrogen atom and a chloride ion to give an elongated rhombic octahedral coordination sphere. The phosphazene ring atoms remain virtually coplanar in all three structures as a consequence of the phenoxy-hinge, which links the pyridine pendant donors to the cyclotriphosphazene platform, allowing the formation of six-membered chelate rings. The spectroscopic (mass spectral, EPR and electronic) and magnetic properties of the complexes are discussed. The EPR and variable temperature magnetic susceptibility results for the dicopper complex, [(CuCl₂)₂(MeL)], point to a very weak electronic interaction between the metal atoms.