Alcoholysis/hydrolysis of 1,1′-carbonyldiimidazole as a means of preparing unprecedented, imidazole-containing one-dimensional coordination polymers of copper(II)

Abstract

The use of 1,1′-carbonyldiimidazole, (im)₂CO, for the synthesis of imidazolate (im⁻) and/or imidazole (Him)-containing copper(II) coordination polymers is described. The [Cu₂(O₂CMe)₄(H₂O)₂]/(im)₂CO reaction system in EtOH yields the new polymeric species [Cu(O₂CMe)(im)(Him)(EtOH)]_n (1) and the known compound [Cu(im)₂]_n (2), depending on the reaction conditions. A mechanism for the alcoholysis/hydrolysis of (im)₂CO is proposed. Complex 1 comprises neutral, zigzag chains with the η¹:η¹:μ im⁻ ligand bridging two neighbouring Cu^II atoms. Each square pyramidal metal centre is coordinated to two imidazolate nitrogen atoms, the pyridine-type nitrogen atom of the terminal imidazole ligand, one acetate oxygen atom and the ethanol oxygen atom. The dc magnetic susceptibility data for 1 have been analysed according to the Bonner-Fisher model for an equally spaced S = 1/2 chain, revealing moderate antiferromagnetic Cu^II⋯Cu^II exchange interactions (J = −33.5 cm⁻¹ using the H = −2J∑Ŝ_iŜ_i+1 spin Hamiltonian). The reaction system Cu(NO₃)₂·3H₂O/(im)₂CO in EtOH leading to the preparation of known trans-[Cu(NO₃)₂(Him)₄] (3) is also described. With terephthalate(−2) (tp²⁻), instead of MeCO₂⁻, in MeOH/H₂O the product is the new, 1D linear coordination polymer [Cu(tp)(Him)₂(H₂O)]_n·2nH₂O (4·2nH₂O). Adjacent square pyramidal Cu^II atoms are singly bridged by the bis-monodentate tp²⁻ ligand, while two monodentate Him groups and one H₂O molecule complete five-coordination at each metal centre. The chains of 1 and 4·2nH₂O form interesting, hydrogen-bonded 3D networks. The combined work demonstrates the usefulness of (im)₂CO in the preparation of interesting Cu^II coordination polymers which can not be obtained by the use of Him.