Polymeric lithium(I) diaquabarbiturate: Crystal structure

Golovnev, N. N.; Molokeev, M. S.; Lesnikov, M. K.; Vereshchagin, S. N. RUSSIAN JOURNAL OF INORGANIC CHEMISTRY, 62 (6):746-750; Doi: 10.1134/S0036023617060092 JUN 2017

The lithium(I) catena-diaquabarbiturate complex [Li(H2O)2(HBA–O,O′)]n (I), where Н2ВА is barbituric acid, has been structurally characterized by X-ray diffraction (CIF file CCDC no. 1447689), and its thermal decomposition and IR spectrum have been studied. Crystals of complex I are monoclinic, a = 6.4306(7) Å, b = 16.720(1) Å, c = 7.1732(8) Å, β = 108.253(4)°, V = 732.5(1) Å3, space group P21/c, and Z = 4. One independent μ2-bridging HBA ligand is coordinated to two Li(I) ions via the two oxygen atoms of C4(6)=O carbonyl groups. Each Li+ ion is linked with two μ2-HBA ions and two terminal water molecules at tetrahedron vertices. μ2-HBA ions link tetrahedra into a chain. The structure is stabilized by multiple hydrogen bonds and π–π-interaction between HBA. The shift of ν(C=O) vibration bands in the IR spectrum of complex I in comparison with Н2ВА towards lower frequencies agrees with the coordination of HBA via oxygen atoms. The dehydration of complex I occurs in two stages in the regions of 100–150 and 150–240°C.

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