On the crystal structures of some protonic complexes of oxo-ligands with tetrachloroauric acid, [(RO)nH][AuCl4] (R: Py, Ph3As; n: 1, 2), prepared from deuterated and non-deuterated solvent systems

The possible structural change of the dimeric cations [(RO)(n)H](+) (R = Py, Ph3As) in [(RO)(n)H][AuCl4] crystals due to the lowering of temperature or hydrogen -deuterium exchange was studied by Cl-35 NQR and powder X-ray diffraction measurements. Temperature dependence of the nuclear quadrupole resonance (NQR) frequencies of [(Ph3AsO)(2)H][AuCl4] and [(PYO)(2)H][AuCl4] suggested the symmetric hydrogen bond was retained down to 4.2 K. A crystalline polymorph of [(PyO)(2)H][AuCl4] (partial deuterate) was found to be stabilized preferably by the deuteration. The crystal structure determination of the partial deuterate by single crystal X-ray diffraction method revealed that the two pyridine N-oxide (PyO) moieties in the dimeric cation [(PyO)(2)H/D] are non-equivalent and the crystal structure is completely different from that of the non-deuterated salt. (C) 2002 Elsevier Science Ltd. All rights reserved.