Hydrogen bonded networks based on lanthanide(III) complexes of N, N′-dimethylurea (DMU): preparation, characterisation, and crystal structures of [Nd(DMU) 6][NdCl 6] and [Nd(NO 3) 3(DMU) 3

Abstract

In order to examine the possibilities of using lanthanide(III) ions in the crystal engineering of hydrogen bonded coordination complexes, the compounds [Ln(DMU) 6][LnCl 6] and [Ln(NO 3) 3(DMU) 3] (Ln=Pr, Nd, Gd, Er; DMU= N, N′-dimethylurea) have been prepared from the reactions of DMU with the appropriate lanthanide(III) salts in alcohols. The representative complexes [Nd(DMU) 6][NdCl 6] ( 2) and [Nd(NO 3) 3(DMU) 3] ( 6) have been structurally characterised by single-crystal X-ray studies. The structure of 2 consists of distorted octahedral [Nd(DMU) 6] 3+ and [NdCl 6] 3− ions. In the molecules of 6, the Nd(III) ion is in a nine-coordinate, monocapped square antiprismatic geometry, surrounded by three O-bonded DMU ligands and three bidentate chelating nitrate groups. The [Nd(DMU) 6] 3+ cations and [NdCl 6] 3− anions self-assemble to form a hydrogen-bonded 3D architecture in 2. The hydrogen bonding functionalities on the molecules of 6 create also a 3D structure. Two main motifs of interionic/intermolecular hydrogen bonds have been observed: NH⋯Cl in 2 and NH⋯O(NO 3 − ) in 6; weak CH⋯Cl hydrogen bonding interactions are also present in 2. The complexes were characterised by magnetic susceptibilities at room temperature and spectroscopic (IR, far-IR, Raman) techniques. The vibrational data are discussed in terms of the nature of bonding and the known structures of the neodymium(III) complexes.