Short hydrogen bond: Spectral studies and X-ray structure of bis(alpha-picoline N-oxide)-hydronium tetrachloroaurate(III)

Abstract

Spectral and the X-ray diffraction studies of the title compound [H(2-picNO) 2] [AuCl 4] (2-picNO = alpha-picoline N-oxide) were done to investigate the short hydrogen bond in the dimeric cation [H(2-picNO) 2] +. The compound exhibits several narrow transmission bands overlaid on a broad continuous absorption characteristic of a short hydrogen bond; it crystallizes with four molecules in a monoclinic unit cell of space group P2 1/n with lattice parameters a = 22.376(9), b = 9.874(6), c = 7.957(5) Å and β = 94.98(6)°. The structure was solved using 2623 data points collected on a CAD4 to the final value for R(F o) = 0.039. The structure consists of discrete [AuCl 4] − and [H(2-picNO) 2] + ions. Contrary to all known examples, the dimeric cation in this compound has a short hydrogen bond having no symmetry constraints making the present structural analysis unique in this series of compounds. The O—O distance is 2.393(6) Å and the dihedral angle between the two planar 2-picNO moieties in the cation is 44.1°. The [AuCl 4] − anion is planar with an average AuCl distance of 2.268(2) Å. The infrared spectrum and the structure of the compound is compared with the related structures.