Synthesis and Crystal Structure of Two Succinato-Bridged Macrocyclic Nickel(II) Complexes

Abstract: Three dinuclear compounds of the types [Mn2(L1)2(μ-ap)(H2O)2](X)2·MeOH·2H2O [X = PF6− (1), BF4− (2)] and [Ni2(L2)2(μ-suc)](PF6)2 (3) [L1 = N,N′-(bis(pyridin-2-yl)benzylidene)-1,3-propanediamine, L2 = N,N′-(bis(pyridin-2-yl)benzylidene)-1,4-butanediamine; ap = adipate dianion and suc = succinate dianion] have been synthesized and X-ray crystallographically characterized. Structural analyses reveal that manganese(II) centers in 1/2 adopt a rare distorted trigonal prismatic geometry whereas nickel(II) centers in 3 are in a distorted octahedral coordination environment each with an MN4O2 chromophore. The ap unit bridges manganese(II) nuclei in 1/2 through its bis(monodentate) mode, whereas the suc connects nickel(II) ions in 3 in bis(bidentate) fashion. Four N atoms of chelated L1, one bridging O atom of ap and the O atom of coordinated water complete hexacoordination around the metal ions in 1/2. Each nickel(II) center in 3 is surrounded by four N atoms of L2 and two bridging O atoms of suc unit. The dinuclear moities in 1/2 are engaged in intramolecular/intermolecular O–H⋯O, O–H⋯F, C–H⋯N and C–H⋯F hydrogen bonds and π⋯π interactions whereas individual units of 3 self-assemble through C–H⋯F and C–H⋯O hydrogen bonds and C–H⋯π interactions in cooperative fashions to promote dimensionalities. Variable-temperature magnetic susceptibility measurements of 1–3 in the 2–300 K temperature range reveal weak antiferromagnetic interaction between two metal(II) centers presumably due to long bridging arm of the dicarboxylates.

Abstract: The reactions of a racemic four-coordinate Ni(II) complex [Ni(rac-L)](ClO4)2 with l- and d-alanine in acetonitrile/water gave two six-coordinate enantiomers formulated as [Ni(RR-L)(l-Ala)](ClO4)·2CH3CN (1) and [Ni(SS-L)(d-Ala)](ClO4) (2) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclo-tetradecane, Ala− = alanine anion), respectively. Evaporation from the remaining solutions gave two four-coordinate enantiomers characterized as [Ni(SS-L)](ClO4)2 (S-3) and [Ni(RR-L)](ClO4)2 (R-3), respectively. Single-crystal X-ray diffraction analyses of complexes 1 and 2 revealed that the Ni(II) atom has a distorted octahedral coordination geometry, being coordinated by four nitrogen atoms of L in a folded configuration, plus one carboxylate oxygen atom and one nitrogen atom of l- or d-Ala− in mutually cis-positions. Complexes 1 and 2 are supramolecular stereoisomers, constructed via hydrogen bonding between [Ni(RR-L)(l-Ala)]+ or [Ni(SS-L)(d-Ala)]+ monomers to form 1D hydrogen-bonded zigzag chains. The homochiral natures of complexes 1 and 2 have been confirmed by CD spectroscopy.

Abstract: A nickel(II) coordination polymer of succinic acid (1,4-butanedioic acid, H2succ), [Ni(succ)(H2O)4]n (1), was prepared and characterized in depth using IR and Raman spectroscopic methods and theore...

Abstract: Three dinuclear isophthalato-bridged nickel(II) complexes formulated as [Ni(rac-L)]2(μ-IPA)(ClO4)2 (1), [Ni(RR-L)]2(μ-IPA)(ClO4)2 (2) and [Ni(SS-L)]2(μ-IPA)(ClO4)2 (3) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyc-lotetradecane, IPA = isophthalic acid) have been isolated and characterized. Single crystal X-ray diffraction analyses revealed that the Ni(II) atoms have six-coordinated distorted octahedral environments, and the isophthalato ligand bridges two Ni(II) centres in a bis bidentate fashion to form dimers in all three complexes. The monomers of {[Ni(SS-L)]2(μ-IPA)} 2+ are connected through intermolecular hydrogen bonds to generate one-dimensional left-handed helical chains in complex 3. The homochiral natures of complexes 2and3have been confirmed by CD spectroscopy.

Abstract: Two dinuclear carbonato-bridged nickel(II) complexes formulated as [Ni(rac-L)]2(µ-CO3)(H2O)(im)4(ClO4)2 (1) and [Ni(SS-L)]2(µ-CO3)(H2O)(im)4(ClO4)2 (2) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, im = imidazole) were isolated from the reactions of [Ni(rac-L)](ClO4)2 and [Ni(SS-L)](ClO4)2 with imidazole in the air, respectively, and a hydrocarbonato-coordinated nickel(II) complex formulated as [Ni(rac-L)](HCO3)(ClO4) (3) was reacted with obtained when [Ni(rac-L)](ClO4)2 reacted with l-cysteine under weakly basic conditions in the air. We found that the macrocyclic nickel(II) complexes can easily take up and fix atmospheric CO2 at room temperature. Single-crystal X-ray diffraction analyses revealed of all three complexes that the central Ni(II) atoms all have a six-coordinated distorted octahedral coordination geometry, and the carbonate anion bridges two Ni(II) atoms in a tridentate fashion to form dimers in complexes 1 and 2, and the hydrocarbonate coordinates with Ni(II) in a didentate fashion in complex 3. The monomers of {[Ni(RR-L)]2(µ-CO3)(H2O)}2+/{[Ni(SS-L)]2(µ-CO3)(H2O)}2+ are connected through hydrogen bonds to generate one-dimensional right- and left-handed helical chains in complex 1. The chiral nature of complex 2 has been confirmed by CD spectroscopy.

Abstract: The Dawson anion P2W18O626− has been used as a noncoordinating polyoxoanion template for the construction of two metal−organic frameworks, namely, [M2(bpy)3(H2O)2(ox)][P2W18O62]2(H2-bpy)·nH2O (M = Co(II), n = 3 (1); M = Ni(II), n = 2 (2)) (bpy = 4,4′-bipyridine; ox = C2O42−). Single-crystal X-ray analysis reveals that both of the structures exhibit 3D host frameworks constructed from the oxalate-bridged binuclear superoctahedron secondary building units (SBUs) and bpy linkers and the voids of which are occupied by Dawson anions, guest bpy, and water molecules. Magnetic studies reveal that there are antiferromagnetic exchange interactions among the transition-metal centers in compounds 1 and 2. Furthermore, a compound 1-modified carbon paste electrode (1-CPE) displays good electrocatalytic activity toward the reduction of nitrite.

Abstract: Three-dimensional open frameworks [Co2(nicotinate)4(μ-H2O)]·CH3CH2OH·H2O, 1, and [Ni2(nicotinate)4(μ-H2O)]·CH3CH2OH·H2O, 2, were obtained by hydro(solvo)thermal reactions between 3-cyanopyridine and cobalt(II) nitrate and nickel(II) perchlorate, respectively. Both 1 and 2 exhibit complicated 3-D structures based on [M2(nicotinate)4(μ-H2O)] (M = Co or Ni) building blocks and possess open channels that are occupied by removable solvent molecules. 3-D open frameworks [M2L4(μ-H2O)]·HL·(H2O)x (where M = Co, x = 2, 3, and M = Ni, x = 1, 4, and L = trans-3-(3-pyridyl)acrylate) were similarly prepared with trans-3-(3-pyridyl)acrylic acid in place of 3-cyanopyridine. Compounds 3 and 4 are isostructural and exhibit network topologies similar to that of 1 with open channels occupied by disordered trans-3-(3-pyridyl)acrylic acid and water guest molecules. Crystal data for 1: triclinic space group P1, a = 10.534(1) A, b = 11.907(1) A, c = 14.046(1) A, α = 106.645(1)°, β = 101.977(1)°, γ = 112.078(1)°, and Z = 4. Cry...

Abstract: Azido–NiII complexes of dinuclear, [Ni2(trpn)2(μ1,3-N3)2](ClO4)2 (1), and monodimensional structures cis-[Ni(abap)(μ1,3-N3)]n(ClO4)n (2) and cis-[Ni(Me6trien)(μ1,3-N3)]n(ClO4)n·nH2O (3a) as well as the monomer [Ni(Me6trien)(N3)]ClO4 (3b) {trpn = tris(3-aminopropyl)amine; abap = N-(2-aminoethyl)-N,N-bis(3-aminopropyl)amine; Me6trien = 1,1,4,7,10,10-hexamethyltriethylene tetramine} were synthesized and structurally characterized by spectroscopic techniques, X-ray crystallography, and variable-temperature magnetic measurements. In the complexes 1–3a, the ClO4– groups are counterions and the Ni2+ centers are bridged by the azido ligands in an end-to-end bonding fashion. The coordination geometry around the NiII ions is six-coordinate with a distorted octahedral environment achieved by the four N atoms of the tetradentate amines and two terminal N atoms of the azide groups. Complex 1 consists of dinuclear units with doubly bridged azido groups whereas in 2 and 3a, a polymeric 1D chain is formed in which the adjacent azido groups link the NiII centers in a cis arrangement. In complex 2, the structural parameters of the two adjacent azido bridging ligands are different and an alternating 1D system with two different end-to-end azido bridges is produced. Complex 3a is a uniform 1D system where the strong steric hindrance imposed by the methyl groups of the Me6trien ligand [diagonal N(azide)–Ni–N(amine) bond angles] causes pronounced deviation from the ideal octahedral geometry. Complex 3b exhibits a distorted square pyramidal geometry. The complexes 1–3a show antiferromagnetic coupling. In complex 1, the exchange coupling constant was J = –64(1) cm–1, whereas in the polynuclear species 2 and 3a, the calculated values were J1 = –63.7(2) (α = 0.52) and J = –26.8(1) cm–1, respectively. The magnetic parameters have been correlated to the structural data.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)