PHASE AND X-RAY STUDY OF CLATHRATE FORMATION IN THE TETRAISOAMYLAMMONIUM FLUORIDE-WATER SYSTEM

The phase diagram of the binary (i-CsH11)4NF-water system has been stu died in the clathrate formation region. Three polyhydrates have been d iscovered, two of which (I : 38.9 and 1 : 32.7) are the known orthorho mbic arid tetragonal phases: Pbmn, a = 11.88, b = 21.53, c = 12.70 ang strom, rho(meas) = 1.019 g cm-3 (0-degrees-C), m.p. = 32.4-degrees-C a nd P4(2)/m, a = 23.729, c = 12.466 angstrom, rho(meas) = 1.062 g cm-3, (0-degrees-C), m.p. = 31.2-degrees-C, respectively. A single crystal X-ray analysis of the novel clathrate hydrate (i-C5H11)4NF . 27 H2O is reported. This new clathrate hydrate is tetragonal, I4(1)/a, with a = 16.894(5), c = 17.111(2) angstrom, Z = 4, (-50-degrees-C), and m.p. = 34.6-degrees-C. Each (i-C5H11)4N+ cation occupies a four-chamber cavi ty built of 15-hedra 7(1)6(3)5(9)4(2) (idealized description), with sm all vacant 5(4)4(4) cavities filling the intervening space.