H. Terao et al., BR-81 NQR AND CRYSTAL-STRUCTURE OF ETHYLAMMONIUM TRIBROMOMERCURATE (II), CH3CH2NH3HGBR3, Zeitschrift fur Naturforschung. A, A journal of physical sciences, 49(1-2), 1994, pp. 202-208
The Br-81 NQR triplet spectrum of (CH3CH2NH)3+(HgBr3)- was measured in
the range 77 K to near the m.p. (99 approximately 106-degrees-C). Nu1
decreases strongly with increasing temperature, exhibiting 136.784 MH
z at 77 K and 128.129 MHz at 298 K. Nu2 decreases from 82.060 MHz at 7
7 K to 76.322 MHz at 298 K. Nu3 increases with temperature, showing nu
3=81.292 MHz at 77 K and 84.903 MHz at 298 K. Replacement of the ammon
ium hydrogens by deuterium produces a negative shift of nu1 and positi
ve ones of nu2 and nu3 at high temperatures. These shifts change with
temperature from \approximately 0\ up to \approximately 200\ kHz. The
crystal structure of the title compound was determined at room tempera
ture: P2(1)/m, Z = 2, a = 1021.6(8) pm, b = 643.0(6) pm, c = 691.8(6)
pm, beta = 96.96(4)-degrees. The coordination of the mercury atom by t
he bromines is trigonal bipyramidal; by formation of bridges Hg...Br..
.Hg by one of the three bromines (Br(2)) of the planar HgBr3- ions a d
ouble chain of trigonal bipyramids is formed, running along the b-axis
of the crystal. Br(1) and Br(3) are single bonded to Hg. The hydrogen
bonds NH...Br(2) and NH...Br(3) (twice), connect the Hg Br chains to
planes lying parallel to the bc plane at x = 0. The relations between
the Br-NQR spectrum and the structure are discussed.