Synthesis and Structure of Ionic Complexes [Ph3PEt][Au(CN)2Cl2] and [Ph3PCH2CH2Br][Au(CN)2Br2]

Abstract

The interaction of potassium dichloro- and dibromodicyanoaurates with the corresponding ethyl- and (2-bromoethyl)triphenylphosphonium halides in water leads to the ionic complexes [Ph₃PEt][Au(CN)₂Cl₂] (1) and [Ph₃PCH₂CH₂Br][Au(CN)₂Br₂] (2), which have been characterized by the X-ray diffraction analysis method. According to the X-ray data, complexes 1 and 2 consist of tetrahedral organyltriphenylphosphonium cations and two types of crystallographically independent centrosymmetric square-planar anions. The phosphorus atoms in organyltriphenylphosphonium cations have a distorted tetrahedral coordination (the CPC bond angles are 107.2(2)–111.4(2)° (1) and 94.4(7)-116.8(9)° (2); the P–C distances are 1.788(4)–1.800(4) Å (1) and 1.694(8)-1.890(8) Å (2)). Centrosymmetric crystallographically independent anions [Au(CN)₂Cl₂]^- (1) have a slightly distorted square-planar geometry, while the geometry of anions [Au(CN)₂Br₂]^– (2) is significantly distorted (the CAuBr cis-angles vary from 74.5(9)° to 105.5(9)°). The Au–Hal (Hal = Cl, Br) bond lengths in the anions are close to the sums of the covalent radii of gold and the corresponding halogen and equal 2.335(3), 2.283(3) Å (1) and 2.536(5), 2.409(7) Å (2); the Au–C bond lengths equal 2.198(11), 2.008(5) Å (1) and 1.95(3), 1.984(8) Å (2) and are close to the sum of the covalent radii of gold and carbon. The structural organization in crystals 1 and 2 is caused by the С–H∙∙∙N≡C hydrogen bonds (2.63 Å (1), 1.86–2.50 Å (2)) and by the additional С–H∙∙∙Br–Au interionic contacts (2.27–2.86 Å) in the case of complex 2.