Crystalline alcoholamine borates and the triborate monoanion.

The triborate and pentaborate compounds 3-hydroxy-2,2-dimethylpropylammonium triborate(1+), [HOCH2C(CH3)2NH3][B3O3(OH)4] (1), and 2-hydroxyethylammonium pentaborate(1-), [HOCH2CH2NH3][B5O6(OH)4].H2O (2), were prepared by crystallization from concentrated aqueous boric acid solutions containing the respective alcoholamines at a boric acid-alcoholamine mole ratio of 3.33:1.00. Compound 1 crystallized in the triclinic space group P1 with a = 5.9595(9) A, b = 6.3024(9) A, c = 15.594(2) A, alpha = 91.218(2) degrees , beta = 91.138(2) degrees , gamma = 118.034(2) degrees , V = 516.56(13) A (3), and Z = 2; 2 crystallized in the monoclinic space group P2 1/ n with a = 11.2469(8) A, b = 9.5091(6) A, c = 11.5422(8) A, beta = 90.175(1) degrees , V = 1234.41(15) A (3), and Z = 4. Compound 1 contains a rare example of a structurally characterized hydroxyl-hydrated triborate monoanion. Comparisons are made with other known examples of this anion.