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All compounds that contain malonate dianions C3H2O42- (mal2-) and atoms of d- or f-metals were analyzed. Dianions mal2- in structures of examined compounds reveal 17 topological types of coordination against metal atoms. Available data shows that mal2- more often form six-membered metal cycles which is the most abundant case for all 570 crystallographic sorts of analyzed mal2- (80%). For those mal2- which form six-membered metal cycles the average observed valence angle SSS is equal to 1200. Results of regression analysis of all mal2- showed linear dependence of ∠SSS on dihedral angel (φ) between planes which go through oxygen and carbon atoms of different carboxyl groups of one anion. For the equation ∠SSS = 124.9 – 0.207φ, correlation coefficient is -0.90. Discovered that in structures of crystals when φ < 600 mal2- necessarily form six-membered metal cycles. Structural slackness of mal2- influence on characteristics of six-membered metal cycles formed by them. Those metal cycles usually have bath conformation. Coordination polymers with fixed type of metal atom and identical type of coordination of mal2- can have different dimension even in the absence of other linkers. This effect is evident on the example of [UO2(mal)(L)]·nH2O compounds. Reportedly [1], change of composition and structure of ligand L lead to changes in the system of intramolecular hydrogen bonds which influence on conformation of six-membered metal cycles. The change of conformation of this cycles lead to different relative spatial distribution of the three uranium atoms, connected with one mal2-. Although of the same stoichiometric composition and crystallochemical role of uranium atoms and coordinated ligand resulting polymeric groups [UO2(mal)(L)] in crystals have different dimension: 3D, 2D or 1D respectively for L – carbamide, water or dimethylacetamide. This work was supported by the base part of the government mandate of the Ministry of Education and Science of the Russian Federation.
