Gold(I) complexes of open-chain and cyclic di-secondary amines

Treatment of N,N'-diisopropyl-ethylenediamine or 1,4-piperazine with two equivalents of [(Ph₃P)Au]₊ BF₄^- leads to binuclear complexes of the diamines: {[(Ph₃P)Au]HN(ⁱPrO)NCH₂-}₂ ²⁺ 2 BF₄^- (1) and {[(Ph₃P)Au]HNCH₂CH₂}₂²⁺ 2 BF₄^- (2), respectively. In the products each quaternary ammonium center bears one gold ligand, one hydrogen atom and two alkyl substituents. The crystal structures of both compounds have been determined. Compound 1 contains discrete ion-triples. The ethylene bridge in the dications is in an unfolded conformation, with a crystallographic center of inversion, and allows for weak hydrogen bonding N-H-F [2.085 Å; N-H-F 169.2°] between the NH functions and the counterions. The existing distant contacts F-Au [3.599 Å] are probably less significant for the aggregation of the ion triples, but will contribute through Coulomb forces. Compound 2 crystallizes with two solvent molecules CH₂Cl₂. The dication has a cryslallographic center of inversion with the piperazine ring in a chair conformation and the gold atoms in equatorial positions. There are hydrogen bonds N-H-F [2.076 and 2.457 Å] between the dication and the anions which lead to the formation of ion-triples, with further contacts between the BF₄^- anions and the solvent molecules [C-H-F 2.340 and 2.446 Å].