Solvothermal Synthesis and Structure of Two New Borates Containing [B7O9(OH)5]2- and [B12O18(OH)6]6- Clusters

Two new metal borates, K[B7O9(OH)(5)]center dot Hen (1, en = enthylenediamine) and Na2Cs4Ba2[B12O18(OH)(6)]center dot 4(OH) (2) have been synthesized under solvothermal conditions. Their structures were determined by the single crystal X-ray diffraction and were further characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis and powder X-ray diffraction, respectively. 1 crystallizes in the triclinic system, P-1 space group, a = 7.7152(6), b = 8.4057(6), c = 12.1319(10) , alpha = 92.505(6), beta = 98.944(7), gamma = 103.825(6)A degrees, Z = 2. 2 crystallizes in the orthorhombic system, Pmn2(1) space group, a = 12.6972(6) , b = 13.7037(6) , c = 9.4968(5) , Z = 2. Compound 1 consists of isolated [B7O9(OH)(5)](2-) clusters which are held together through H-bonding interactions and K atoms to form a 3-D supramolecular framework. For 2, bowl-like isolated [B12O18(OH)(6)](6-) clusters were linked together to form a 3-D framework by different metal ions and H-bond system.