An alternating copper(II) chain with bridging azide and oxamidate ligands: crystal structure and magnetic properties of [Cu2(dmaeoxd)(N3)2(H2O)2] and [{Cu2(dmaeoxd)(N3)2}N]{H2dmaeoxd =N,N′-bis[2-(dimethylamino)ethyl]oxamide}

Abstract

Two new azide-containing complexes [Cu₂(dmaeoxd)(N₃)₂(H₂O)₂]1 and [{Cu₂(dmaeoxd)(N₃)₂}_n]2{H₂dmaeoxd =N,N′-bis[2-(dimethylamino)ethyl]oxamide} have been synthesized and characterized by single-crystal X-ray diffraction methods: 1, triclinic, space group P= 8.620(3), b= 9.824(3), c= 11.216(3)Å, α= 85.56(3), β= 86.90(3), γ= 89.98(3)° and Z= 2; 2, monoclinic, space group P2₁/n, a= 9.1 85(1), b= 11.477(4), c= 7.917(3)Å, β= 100.88(3)° and Z= 2. The structure of 1 is made up of two neutral centrosymmetric trans oxamidate-bridged copper(II) dinuclear units with unidentate azide ligands and weakly co-ordinated water molecules. Each copper atom has a distorted square-pyramidal geometry with an oxygen and two nitrogen atoms from the oxamidate group and one nitrogen atom from the azide group forming the equatorial plane and one oxygen atom from water at the axial position. The structure of 2 consists of neutral chains of copper(II) with an alternating azide–oxamidate bridging arrangement. The oxamidate group acts as a bis(terdentate) ligand as in 1 and the azide bridges the metal atoms in an asymmetrical end-on fashion. Each copper atom has a distorted square-pyramidal geometry with one oxygen and two nitrogen atoms from the oxamidate ligand and one nitrogen atom from the azide group in the equatorial plane, whereas the axial position is occupied by a nitrogen atom of another azide group. The metal–metal separation through the oxamidate in each compound is very similar [5.202(1) and 5.232(1) in 1 and 5.286(1)Å in 2] and much larger than that through azide in 2[3.395(1)Å]. An investigation of the magnetic properties of 1 and 2 in the temperature range 80–300 K revealed the occurrence of strong antiferromagnetic interactions through oxamidate in both compounds and a weaker ferromagnetic coupling through the end-on azide bridge in 2.