N-H•••S hydrogen bonds in a new family of ion-pair complexes between cationic nickel tetraazabicyclononane and anionic metal dithiolates:: Synthesis, characterization and properties of [Ni(C9H22N6)][M(mnt)2] (MII = Cu, Ni, Pd)

The ion-pair complexes [Ni(C9H22N6)][Cu(mnt)(2)] (1), [Ni(C9H22N6)][Ni(mnt)(2)] (2), and [Ni(C9H22N6)][Pd(mnt)(2)] (3; mnt(2-) = 1,2-dicyanoethylenedithiolate, C9H22N6 = 3,7-bis(2aminoethyl)-1,3,5,7-tetraazabicyclo[3.3.1]nonane) have been synthesized and characterized by elemental analysis, IR, UV/Vis, and H-1 NMR spectroscopy, X-ray powder diffraction, and electrochemical studies, and unambiguously by single-crystal X-ray crystallography. All three complexes are isostructural and crystallize in the monoclinic space group P2(1)/n. The N-(HS)-S-...-type hydrogen-bonding capabilities of the classical sulfur-containing complex anions [M-II(mnt)(2)](2-)(A; M = Cu, Ni and Pd) have been explored using amine groups containing the nickel complex cation [Ni(C9H22N6)](2+) (C) in the ion-pair compounds 1, 2, and 3. In the crystal, the cation interacts with two different anions through three N-(HS)-S-... hydrogen bonds and, likewise, the anion is hydrogen-bonded to two different cations through three hydrogen bonds, resulting in the formation of a chain-like arrangement. The average N-H...S hydrogen-bond lengths are 3.498(3), 3.505(3), and 3.490(5) angstrom for compounds 1, 2, and 3, respectively. Another crystallographic feature is the presence of CC-AA-CC-AA-type packing with short (SNi)-Ni-... contacts in the crystal structures. Besides crystallography, the existence of these N-(HS)-S-... hydrogen bonds between cation [Ni(C9H22N6)](2+) (C) and anion [M-II(mnt)(2)](2-) (A) is strongly supported by the IR and H-1 NMR studies. The stability of the [Ni(C9H22N6)](2+) (C) moiety in compounds 1, 2, and 3 is discussed in light of electrochemical studies performed on these compounds and [Ni(C9H22N6)](ClO4)(2). Complex 1 exhibits a well-resolved ESR signal corresponding to a Cu2+ (d(9)) system at liquid-nitrogen temperature. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)