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(C < inf > 9 < /inf > H < inf > 22 < /inf > N < inf > 6 < /inf > )][M(mnt) < inf > 2 < /inf > ] (M < sup > II < /sup > = Cu, Ni, Pd)

Abstract

The ion-pair complexes [Ni(C9H22N6)] [Cu(mnt)2] (1), [Ni(C9H22N6)] [Ni(mnt)2] (2), and [Ni(C9H22N 6)][Pd(mnt)2] (3; mnt2- = 1,2- dicyanoethylenedithiolate, C9H22N6 = 3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo[3.3.1]nonane) have been synthesized and characterized by elemental analysis, IR, UV/ Vis, and 1H 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 P21/n. The N-H⋯S-type hydrogen-bonding capabilities of the classical sulfur-containing complex anions [MII(mnt) 2]2- (A; M = Cu, Ni and Pd) have been explored using amine groups containing the nickel complex cation [Ni(C9H 22N6)]2+ (C) in the ion-pair compounds 1, 2, and 3. In the crystal, the cation interacts with two different anions through three N-H⋯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) Å for compounds 1, 2, and 3, respectively. Another crystallographic feature is the presence of CC-AA-CC-AA-type packing with short S⋯Ni contacts in the crystal structures. Besides crystallography, the existence of these N-H⋯S hydrogen bonds between cation [Ni(C9H22N 6)]2+ (C) and anion [MII(mnt)2] 2- (A) is strongly supported by the IR and 1H 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(C9H 22N6)](ClO4)2. Complex 1 exhibits a well-resolved ESR signal corresponding to a Cu2+ (d9) system at liquid-nitrogen temperature. © Wiley-VCH Verlag GmbH & Co. KGaA, 2006.