CRYSTAL-STRUCTURE AND DEHYDRATION PROCESS OF LI(H2O)(4)B(OH)(4)CENTER-DOT-2H2O

Li(H2O)(4)B(OH)(4).2H(2)O crystallizes in the trigonal system, space g roup P3, with a = 6.5534(5) Angstrom, c = 6.1740(7) Angstrom (T = 293 K), and Z = 1. In this compound, there are isolated Li(H2O)(4) and B(O H)(4) tetrahedra which are almost regular. Some of the positions of hy drogen atoms were localized with an occupancy factor of 2/3 and 1/3; t herefore, all the numerous hydrogen bonds present in the structure wer e well determined. Knowledge of the structure allows us to propose a d ehydration process of three steps; there is a loss of free water molec ules (2H(2)O) from 60 degrees C followed by a loss of lithium-coordina ted water molecules (4H(2)O). This leads to an intermediate berate LiB (OH)(4) whose structure is known. The final dehydroxylation occurs at 170 degrees C. Some comparisons are made between the structures of LiB (OH)(4) and Li(H2O)(4)B(OH)(4).2H(2)O, especially considering the hydr ogen bonds. (C) 1995 Academic Press, Inc.