Temperature Dependence of 35Cl Nuclear Quadrupole Resonance Frequencies and Hydrogen Bonding in Some Metal(II) Hexachlorostannate(IV) Hexahydrates

The 35 C1 NQR frequencies in MgTeCl 6 • 6 H 2 0, NiTeCl 6 • 6 H 2 0, and NiIrCl 6 • 6 H 2 0 have been determined at various temperatures. These compounds form rhombohedral crystals with the space group R3, showing a single resonance line. The 35 C1 NQR frequencies of the Te(IV) complexes exhibit an unusual positive temperature coefficient. The deuterated analogs of the Te(IV) complexes show a small frequency shift at 77 K. These results are interpreted by the presene of O-H • • • CI type weak H-bonds. The resonance frequency of the Ir(IV) complex versus temperature curve shows a minimum and a maximum. This unusual temperature dependence is mainly explained by the same type of the H-bond as existing in the Te(IV) complexes. The 7r-bond formation between Ir and CI atoms is also partly responsible for the unusual temperature dependence.

Section: Anomalous Temperature Dependence Of Nqr Frequenciessupporting

confidence: 63%

“…Kitazume [3]. The anomaly was interpreted in terms of the O-H • • • CI type H-bond formed, and this was well supported through the 35 C1 NQR studies of the deuterated analogs.…”

Section: Introductionmentioning

confidence: 67%

Temperature Dependence Studies of 35^{Cl NQR Frequencies in Magnesium and Nickel Hexachlorotellurate(IV) Hexahydrates and Nickel Hexachloroiridate(IV) Hexahydrate}

Sasane

Fukumitsu

Mori

et al. 1990

“…In this instance the resonant atom may show a larger negative temperature dependence because N z is increased not only by the usual librations but also by the weakening of the H-bond with increasing temperature. The observed frequency shifts are small and also comparable to the deuteration isotope effects in the case of the hexachlorometalate salts with the waters of crystallization [5]. The X H-2 D isotope effects in the latter compounds have been well explained on the assumption that the H-bonds are directed to the p x and/or p y lone pairs of electrons: (i) At the low temperature limit, the molecular motions are well sup-pressed and only the low frequency lattice vibrations exist; the frequency of the resonant atoms is lowered by the deuteration because the D atom is able to approach in a shorter distance to the resonant atom due to its heavier mass than the H atom [7].…”

mentioning

confidence: 56%

“…The strength of the H-bonds in the present crystals may be compatible with that of the H-bonds, O-H • • • X, in the hexachlorometalate salts with the waters of crystallization. The effect of H-bonds on 35 C1 NQR frequencies of these compounds has been extensively investigated by Nakamura et al [5]. They suggested that the H-bonding affects the resonance frequencies of the H-bonded CI atoms according to the following mechanism.…”

mentioning

confidence: 99%

⁸¹Br and ¹²⁷ I NQR Studies of (CH₃NH₃)₂HgBr₄ and (CH₃NH₃)₂HgI₄

Terao

Okuda

Minami

et al. 1992

2 HgBr 4 . Both negative and positive frequency differences between the deuterated and the nondeuterated compound have been observed at 77 K. The relatively large asymmetry parameters in the iodine compound decrease with increasing temperature, indicating the existence of H-bonds. The present results are interpreted qualitatively by considering the effects of H-bonding, N-H • • • X, between the halogen atoms and the CH 3 NH 3 ions which may undergo large molecular motions. It is suggested that not only frequency-lowering but also frequency-rising effects may be produced, depending on the direction of the H-bond, i.e., the angle between the Hg-X bond and the X • • • H bond.

“…35 C1 NQR studies [1][2][3][4] ,v : Pt, Sn), consisting of octahedral cations and anions with an isomorphous rhombohedral structure (space group R 3), have been investigated to reveal inter-molecular paramagnetic interactions and molecular motion in both ions. In such 35 C1 NQR relaxation measurements [5][6][7][8][9][10] several kinds of motion in the cations and anions were found to be excited above ca.…”

Section: Introductionmentioning

confidence: 99%

Temperature Dependence of ²H Quadrupole Coupling Constants in ²H₂O and Ionic Motions in Crystalline [M(²H₂O)₆] [SnCl₆] (M: Mg, Ca), Studied by ²H NMR and Neutron Powder Diffraction

Yoshida

Onoda-Yamamuro

Ishimaru

et al. 1998

Self Cite

The temperature dependence of 2 H NMR spectra was measured at 130-430 K on [M(D 2 0) 6 ] [SnCl 6 ] (M : Mg, Ca) (rhombohedral, space group: R3), and neutron powder diffraction on the Mg salt was performed at room temperature. Based on the accurate orientation of D 2 0 molecules in an octahedral cation, spectra with a large asymmetry parameter rj, observed around 200 K, were explained by a model of 180° flip of water molecules. Another motional narrowing observed above room temperature was assigned to a cationic overall reorientation about the C 3 -axis.