Organyltriphenylphosphonium dichlorodicyanoaurates [Ph3PR][Au(CN)2Cl2] (R=n-Pr, i-Bu, n-Hp): synthesis and structure

The interaction of potassium dichlorodicyanoaurate with n-propyl-, i-butyl- and n-heptyltriphenylphosphonium bromides in water followed by the recrystallization from acetonitrile leads to the dichlorodicyanoaurate complexes [Ph3P(n-Pr)][Au(CN)2Cl2] (1), [Ph3P(i-Bu)][Au(CN)2Cl2] (2), and [Ph3P(n-Hp)][Au(CN)2Cl2] (3). Compounds 1 and 2 have been identified by the IR spectroscopy; structure of compound 3 has been determined by the X-ray diffraction analysis. According to the X-ray data, complex 3 consists of n-heptyltriphenylphosphonium cation and two types of crystallographically independent centrosymmetric square-planar dichlorodicyanoaurate anions. The phosphorus atom in the cation has a slightly distorted tetrahedral coordination with the CPC bond angles within the interval 108.3(5)-110.5(5)°; the P-C distances are 1.801(10)-1.832(10) Å. The square-planar coordination of the gold atoms in centrosymmetric anions [Au(CN)2Cl2]- is almost undistorted: the CAuC and ClAuCl trans-angles equal 180°, the CAuCl cis-angles vary in a narrow range 74.5(9)-105.5(9)°. The Au-Cl bond lengths in anions do not exceed the sum of the covalent radii of the gold and chlorine atoms and equal 2.406(3), 2.388(3) Å; the Au-C bond lengths are 2.021(14), 2.037(13); they are close to the sum of the covalent radii of the gold and carbon atoms. The structural organization in crystals 3 is caused by the H∙∙∙N≡C (2.55-2.63 Å) and C-H∙∙∙Cl-Au (2.87 Å) hydrogen bonds. Moreover, the structure contains the additional C-H∙∙∙π(Ph) contacts with the distances from the hydrogen atom to the plane of the benzene ring that are equal to 2.80 Å. Complete tables of atomic coordinates, bond lengths, and valence angles are deposited in the Cambridge structural data Bank (No. 2094701 for 3; deposit@ccdc.cam.ac.uk; http://www.ccdc.cam.ac.uk).