Crystal structures of five gold(I) complexes with methyl-piperidine ligands

In bis-(4-methyl-piperidine-κN)gold(I) chloride, [Au(C₆H₁₃N)₂]Cl (1), the methyl groups are, as expected, equatorial at the piperidine ring, but the Au atom is axial; this is the case for all five structures reported here, as is the expected linear coordination at the Au atom. Hydrogen bonding of the form N-H⋯Cl^-⋯H-N leads to inversion-symmetric dimers, which are further connected by C-H⋯Au contacts. Bis(4-methyl-piperidine-κN)gold(I) di-chlorido-aurate(I), [Au(C₆H₁₃N)₂][AuCl₂] (2), also forms inversion-symmetric dimers; these involve aurophilic inter-actions and three-centre hydrogen bonds of the form NH(⋯Cl)₂. Bis(4-methyl-piperidine-κN)gold(I) di-bromido-aurate(I), [Au(C₆H₁₃N)₂][AuBr₂] (3), is isotypic to 2. The 1:1 adduct chlorido-(4-methyl-piperidine-κN)gold(I) bis-(4-methyl-piperidine-κN)gold(I) chloride, [Au(C₆H₁₃N)₂]Cl·[AuCl(C₆H₁₃N)] (4), crystallizes as its di-chloro-methane solvate. The asymmetric unit contains two formula units, in each of which the chloride anion accepts a hydrogen bond from the cation and from the neutral mol-ecule, and the two Au atoms are linked via an aurophilic inter-action. A further hydrogen bond leads to inversion-symmetric dimers. The asymmetric unit of bis-(2-methyl-piperidine-κN)gold(I) chloride, [Au(C₆H₁₃N)₂]Cl (5), contains two 'half' cations, in which the Au atoms lie on twofold axes, and a chloride ion on a general position. Within each cation, the relative configurations at the atoms N and C2 (which bears the methyl substituent) are R,S. The twofold-symmetric dimer involves two N-H⋯Cl^-⋯H-N units and an aurophilic contact between the two Au atoms.