Synthesis, crystal structure and magnetic properties of two alternating double μ_1,1 and μ_1,3 azido bridged Cu(II) and Ni(II) chains

Abstract

Two new alternating μ_1,1- and μ_1,3-azido bridged chains, [Cu(N₃)₂(mtn)]_n (1) and [Ni(N₃)₂(mtn)]_n (2) where mtn = N-methyl-1,3-propanediamine, have been synthesized and characterized by single crystal X-ray diffraction. In both complexes, each metal atom is coordinated to six nitrogen atoms from four azide anions and one N-methyl-1,3-propanediamine molecule in a distorted octahedral geometry. In 1, the basal-apical double μ_1,1-azido bridged Cu(II)-dimers are connected through two asymmetric μ_1,3-N₃ bridges to form a 1D chain in which one of the azide acts as a μ_1,1,3 bridge while the other one is terminal. The structure of 2 is very similar but one of the azide ions acts as μ_1,1 and the other as μ_1,3 to form an alternating chain. Magnetic data of both compounds were fitted to an alternating ferro/antiferromagnetic chain model (g = 2.120, J_F = +15.6 cm⁻¹, J_AF = −2.6 cm⁻¹ and a paramagnetic impurity of ca. 0.4% for 1 and g = 2.180, J_F = +23 cm⁻¹ and J_AF = −33 cm⁻¹ for 2).