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Two New Potassium Borates, K4B10O15(OH)4 with Stepped Chain and KB5O7(OH)2·H2O with Double Helical Chain

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posted on 2005-01-05, 00:00 authored by Hong-Xia Zhang, Jie Zhang, Shou-Tian Zheng, Guo-Yu Yang
Two unusual chainlike potassium borates of K4B10O15(OH)4 (1) and KB5O7(OH)2·H2O (2) have been synthesized under mild solvothermal conditions at 170 °C. The structures were determined by single-crystal X-ray diffraction and further characterized by FTIR, powder X-ray diffraction, and thermogravimetric analysis. Compound 1 crystallized in the monoclinic space group C2/c, a = 18.077(6) Å, b = 6.857(2) Å, c = 13.266(4) Å, β = 95.271(4)°, V = 1637.4(9) Å3, Z = 4, R = 0.0234; and compound 2 crystallized in the monoclinic space group P2(1)/c, a = 9.4824(8) Å, b = 7.5180(6) Å, c = 11.4154(6) Å, β = 97.277(3)°, V = 807.2(1) Å3, Z = 4, R = 0.0502. The stepped chains of 1 are built up from corner sharing of B3O5(OH)23- and B4O96- groups to form new fundamental building blocks (FBBs) of B5O10(OH)27- constructed by corner sharing of one B3O5(OH)23- cluster with a three-membered ring, one BO33- unit, and BO45- tetrahedron, while the double helical chain of 2 is built up by FBBs of B5O7(OH)2-. Adjacent chains in 1 and 2 are further connected into a 3-D structure by K+ cations and H-bonding interactions.

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