Synthesis, crystal structures and spectroscopic studies of praseodymium(III) malonate complexes

Abstract

Reactions of malonic acid (H 2mal) with PrCl 3·6H 2O afforded the known complex [Pr 2(mal) 3(H 2O) 6] n ( 1), and compounds [Pr 2(mal) 3(H 2O) 6] n ·2 nH 2O ( 2·2 nH 2O), [PrCl(mal)(H 2O) 3] n ·0.5 nH 2O ( 3·0.5 nH 2O) and [Pr(mal)(Hmal)(H 2O) 3] n · nH 2O ( 4· nH 2O) using various reaction ratios, reaction media (H 2O, MeOH) and pH values. Analogous reactions with CeCl 3·7H 2O afforded compounds [Ce 2(mal) 3(H 2O) 6] n ( 5), [CeCl(mal)(H 2O) 3] n · nH 2O ( 6· nH 2O) and [Ce(mal)(Hmal)(H 2O) 3] n · nH 2O ( 7· nH 2O). Compounds 2·2 nH 2O and 3·0.5 nH 2O were characterized by X-ray crystallography, and 4– 7 by microanalytical and spectroscopic data. The malonate(-2) ligand adopts three different coordination modes in the structures of 1– 3, i.e., the μ 2-κ O:κ O′:κ O″ and the μ 4-κ 2 O:κ O′:κ 2 O″:κ O‴ in 1 and 2 leading to a 3D network structure, and the μ 3-κ 2 O:κ O′:κ 2 O″:κ O‴ in 3 promoting an 1D structure. The thermal decomposition of 1 and 3·0.5 nH 2O was monitored by TG/DTA and TG/DTG measurements. The structural features of 1– 3 are discussed in terms of known malonato(-2) Ln III and Ca II complexes. The bioinorganic chemistry relevance of our results is discussed.