81Br NQR and Crystal Structure of Ethylammonium Tribromomercurate(II), CH3CH2NH3HgBr3

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Abstract The 81Br NQR triplet spectrum of (CH3CH2NH)3 ⊕(HgBr3)⊖ was measured in the range 77 K to near the m.p. (99~106°C) v1 decreases strongly with increasing temperature, exhibiting 136.784 MHz at 77 K and 128.129 MHz at 298 K. v2 decreases from 82.060 MHz at 77 K to 76.322 MHz at 298 K. v3 increases with temperature, showing v3 = 81.292 MHz at 77 K and 84.903 MHz at 298 K. Replacement of the ammonium hydrogens by deuterium produces a negative shift of v1 and positive ones of v2 and v3 at high temperatures. These shifts change with temperature from |~ 0| up to |~ 200| kHz. The crystal structure of the title compound was determined at room temperature: P 21/m, Z = 2, a = 1021.6(8) pm, b = 643.0(6) pm, c = 691.8(6) pm, β = 96.96 (4)°. The coordination of the mercury atom by the bromines is trigonal bipyramidal; by formation of bridges Hg··· Br··· Hg by one of the three bromines (Br(2)) of the planar HgBr⊖ ions a double 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 N -H···Br(1) and N -H ··· Br(3) (twice), connect the Hg-Br chains to planes lying parallel to the be plane at x = 0. The relations between the Br-NQR spectrum and the structure are discussed.