Crystal structures of five gold(I) complexes with methylpiperidine ligands

In bis(4-methylpiperidine-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-methylpiperidine-κN)gold(I) dichloridoaurate(I), [Au(C6H13N)2][AuCl2] (2), also forms inversion-symmetric dimers; these involve aurophilic interactions and three-centre hydrogen bonds of the form NH(...Cl)2. Bis(4-methylpiperidine-κN)gold(I) dibromidoaurate(I), [Au(C6H13N)2][AuBr2] (3), is isotypic to 2. The 1:1 adduct chlorido(4-methylpiperidine-κN)gold(I) bis(4-methylpiperidine-κN)gold(I) chloride, [Au(C6H13N)2]Cl·[AuCl(C6H13N)] (4), crystallizes as its dichloromethane 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 molecule, and the two Au atoms are linked via an aurophilic interaction. A further hydrogen bond leads to inversion-symmetric dimers. The asymmetric unit of bis(2-methylpiperidine-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.