SYNTHESIS AND STRUCTURE OF METHYLTRIPHENYLPHOSPHONIUM DICYANODIBROMOAURATE [Ph3PCH3] [Au(CN)2Br2

Abstract

Methyltriphenylphosphonium dicyanodibromoaurate (1) [Ph3PMe]+[Au(CN)2Br2]– was synthesized by the reaction of potassium dicyanodibromoaurate with methyltriphenylphosphonium bromide in an aqueous solution and was structurally characterized. The complex is a yellow-colored, air-resistant crystalline substance with a clear melting point. The structure of the compound was established by IR spectroscopy, NMR spectroscopy and X-ray diffraction analysis. An intense absorption band was observed in the IR spectrum of compound at 2220 cm−1, corresponding to the stretching vibrations of cyano groups. The absorption band of the deformation vibrations of the P – СPh bonds in the IR spectrum is at 1438 cm−1. In the recorded 1Н, 13С, and 31Р NMR spectra, signals are observed for the number, value of chemical shifts and integral intensity that do not contradict the proposed complex structure. The X-ray diffraction analysis of crystal 1 was carried out on a Bruker D8 QUEST diffractometer (MoKα radiation, λ = 0.71073 Å, graphite monochromator). [C21H18AuBr2N2P, M = 686.13, crystal system triclinic, space group P-1, a = 8.802(5), b = 8.989(5), c = 15.233(11) Å, V = 1143.8(13) Å3, Z = 2, µ = 10.002 mm-1, F(000) = 644, crystal size 0.41×0.30×0.22 mm]. According to the X-ray diffraction analysis (XRDA) data there are two types of centrosymmetric crystallographically independent monomeric dicyanodibromoaurate anions and methyltriphenylphosphonium cations in the crystal of compound MFDDA. The cations have a distorted tetrahedral configuration: the CPC angles equal 108.8(2)°−110.0(2)°, the P−С distances are 1.791(5)−1.800(5) Å. All СAuC and BrAuBr trans-angles are 180.0° in the [Au(CN)2Br2]− anions. The Au−C distances in anions differ from each other and equal 2.040(7), 2.024(1), 1.991(2) Å. These values are close to the sum of the covalent radii of atoms (2.03 Å). The Au-Br bond lengths are equal to 2.4162(14), 2.4591, 2.474(5) Å in dicyanodibromoaurate anions. Formation of the crystal structure occurs due to formation of weak N···Н−С hydrogen bonds between cations and anions (2.68, 2.59, 2.38 Å) and Br···Н−С (3.03, 3.02 Å). Complete tables of coordinates of atoms, bond lengths and valence angles are deposited at the Cambridge Crystallographic Data Centre.