Synthesis and characterisation of uranyl substituted malonato complexes Part I. Structural diversity with dimethylmalonate and different counter-cations

Uranyl dimethylmalonato complexes with different metal to ligand ratios and connectivity, 1:2 monomeric, dimeric and 2:3, 3:4 infinite chain structures have been prepared and characterised by elemental analysis, thermal analysis, IR and C-13 CPMAS NMR spectroscopy, and X-ray crystallography. The different structural types are isolated by the use of different counter-cations. Two new kinds of binding mode of malonate with uranyl have been identified, tridentate (mu(2) 1,3-bidentate and 1,5-bidentate) and tetradentate (1,3-bidentate with both carboxylate groups). A basis for the prediction of structural type from the results of C-13 CPMAS NMR spectroscopy is proposed. The structures of the crystallographically characterised products can be rationalised in terms of templating by the counter-cations, which appears to be influenced by the size of the counter-cations and the tendency to maximise hydrogen bonding in the lattice. (C) 2002 Elsevier Science Ltd. All rights reserved.