On the Order‐Disorder Phase Transition of Anilinium Halides. Crystal Structure of the High and Low Temperature Phase of Anilinium Iodide, C6H5NHI⊖ (C6D5NHI−). X‐Ray and Neutron Diffraction Studies

The crystal structure of the high temperature phase I of anilinium iodide, C6H5NH ⊕3I⊖, was determined by X‐ray and neutron diffraction at T = 294 K: D 102h‐Pnaa, Z = 4, a = 1738.2(10) pm, b = 636.3(5) pm, c = 703.9(5) pm, ϱcalc = 1.886 Mgm−3. At Tc = 241 K, a ferroelastic phase transition occurs. The crystal structure of the low temperature phase II was studied on C6D5NH ⊕3I⊖ by neutron diffraction at T = 140K: C52h‐P21/a, Z = 4, a = 1753.8(10) pm, b = 614.2(5) pm, c = 706.5(5) pm, β = 90.79(1)°, ϱcalc = 1.973 Mgm−3. Phase I is disordered with respect to four different positions of the −NH ⊕3 group, whereas phase II is ordered. The present results are compared with the crystal structures and the phase transition of anilinium bromide, C6H5NH ⊕3Br⊖. The mechanism of the phase transition is discussed.

On the Order‐Disorder Phase Transition of Anilinium Halides. Crystal Structure of the High and Low Temperature Phase of Anilinium Iodide, C₆H₅NHI^⊖ (C₆D₅NHI⁻). X‐Ray and Neutron Diffraction Studies

Fecher¹,

Weiß²

1986

On the Order‐Disorder Phase Transition of Anilinium Halides. ¹²⁷I‐NQR Investigation of the Anilinium Iodides C₆H₅NHI^⊖, C₆H₅NDI^⊖, C₆D₅NHI^⊖, and C₆D₅NDI^⊖. Dilatometric Studies on Anilinium Bromide and Anilinium Iodide Single Crystals

Feeder

Weiß

1986

Self Cite

127I‐NQR measurements in the range 77 ≤ T/K ≤ 520 are reported for anilinium iodides C6H5NH⊕3I⊖, C6H5ND⊕3I⊖, C6D5NH⊕3I⊖, and C6D5ND⊕3I⊖. The compound undergoes a ferroelastic phase transition at 240.3 K (C6H5NH⊕3I⊖). The transition temperature changes to 233.6 K (C6H5ND⊕3I⊖) and to 233.4 K (C6D5ND⊕3I⊖) by deuteration. The NQR parameters are thereby influenced too. At 293 K the −NH⊕3 group deuteration influences e2ϕzzQh−1 and η much stronger than the ring deuteration, whereas at 77 K these effects are of comparable magnitude.—The thermal expansion coefficients were measured for C6H5NH⊕3X⊕, X = Br, I, from 120 K to 300 K. by dilatometry and by X‐ray diffraction. In C6H5NH⊕3Br⊖ the three linear expansion coefficients are increasing over the whole temperature range studied, whereas in C6H5NH⊕3I⊖ α[010] increases and both, α[100] and α[001], decrease with increasing temperature. On hand of the known crystal structures the ferroelastic phase transition in the anilinium halides is discussed. The basic mechanism of the transition is the same for C6H5NH⊕3I⊖ and C6H5NH⊕3Br⊖. Freezing in of the −NH⊕3 group hindered rotation is the main process governing the phase transitions, but motions of the phenyl ring are of influence, too.

Structure, Hydrogen Bonds and Phase Transition in Ethylenediammonium Hexachlorometallates, [H₃N(CH₂)₂NH₃]^2⊕ [XCI₆]^2⊖, X = Sn, Pb, Te, Pt. A ³⁵Cl NQR and X‐ray Diffraction Study

Borchers

Weiß

1986

Complex Compounds J Crystal Structure 1 Isotope Effects 1 Phase Transitions 1 Spectroscopy, Nuclear Quadrupole ResonanceThe crystal structure and chemical bond of ethylenediarnmonium hexachlorometallates, [H3N(CH2)2NH3] [xc16] 2Q, X = Sn, Pb, Te, Pt, was studied by X-ray diffraction and 35C1 NQR. [H3N(CH2)2NH3]2e [SnC16]2Q crystallizes with the space group Cf-Pi, Z = 1. The lattice constants are a = 704.4 pm, b = 711.2 pm, c = 743.7 pm, CI = 67.537-", p = 65.341", y = 60.407". The crystal structure was determined. It is described by a deformed CsC1-type lattice and the hydrogen bonds N -H . . . C1 cause a weak layer type solid. The compounds with X = Sn, Pb, Te, Pt are isotypic and the lattice constants are given. A three line 35Cl NQR spectrum is observed for all compounds in the temperature range 77 5 T/K 5 decomposition temperature, in agreement with the crystal structure. The hexachloroplatinate experiences a phase transition at T = 357.2 K, the high temperature phase I being of higher symmetry than P i . This shows up in the two line 35Cl NQR spectrum in phase I. Isotope exchange H + D at the ammonium groups influences T, and v(~'CI) slightly, an observation, which favours the assumption of rather weak hydrogen bonds N -H ... C1.