Hydrogen bonded networks based on lanthanide(III) complexes of N,N′-dimethylurea (DMU):: preparation, characterisation, and crystal structures of [Nd(DMU)6][NdCl6] and [Nd(NO3)3(DMU)3]

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(NO3)(3)(DMU)(3)] (Ln = Pr, Nd, Gd, Er; DMU = N,N'-dimethylurea) have been prepared from the reactions of DMU with the appropriate lanthaniae(III) salts in alcohols. The representative complexes [Nd(DMU)(6)][NdCl6] (2) and [Nd(NO3)(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 [NdCl6](3-) ions. In the molecules of 6, the Nd(III) ion is in a ninecoordinate, monocapped square antiprismatic geometry, surrounded by three O-bonded DMU ligands and three bidentate chelating nitrate groups. The [Nd(DMU)(6)](3+) cations and [NdCl6](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(NO3-) 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. (C) 2003 Elsevier Science Ltd. All rights reserved.