Nickel Coordination Polymers Research Articles

A 1D thiocyanato bridge nickel(II) system: crystal structure and magnetic property

A one-dimensional coordination polymer of nickel(II), [(μ N,S-NCS) 2{Ni(ampy)}] n (ampy=1-(2-aminoethyl)pyrrolidine) has been synthesized and characterized by X-ray single crystal analysis. Structure analysis reveals that each nickel(II) center is coordinated in a distorted octahedral fashion with four bridging thiocyanato ligands and one mesocyclic diamine ligand. The low temperature (300–18 K) magnetic measurement shows that the system is ferromagnetically coupled. The magnetic data are fitted to the de Neef equation, giving the parameters J=1.4 cm −1 and g=2.08.

Synthesis and X-ray Powder Structures of Nickel(II) and Copper(II) Coordination Polymers with 2,5-Bis(2-pyridyl)pyrazine.

The reaction of 2,5-bis(2-pyridyl)pyrazine (bppz) with nickel(II) sulfate in aqueous solution yielded a binuclear complex, [Ni(2)(bppz)(H(2)O)(8)](SO(4))(2).2H(2)O (1), whose structure was solved by single-crystal methods. The compound crystallizes in the monoclinic space group P2(1)/n with a = 8.372(2) Å, b = 18.301(2) Å, c = 17.197(2) Å, beta = 97.54(2) degrees, and Z = 4. The bppz ligand chelates the two octahedrally coordinated nickel atoms through its nitrogen donors. The four remaining coordination sites are occupied by water oxygen atoms. The binuclear [Ni(2)(bppz)(H(2)O)(8)](4+) cations are held together by hydrogen bonds involving sulfate anions and water molecules. Similar reactions with nickel(II) or copper(II) chloride in less polar solvents resulted in the formation of two new coordination polymers, {[Ni(2)Cl(2)(bppz)(H(2)O)(2)(CH(3)OH)(2)]Cl(2)}(n)() (2) and [Cu(2)Cl(4)(bppz)](n)() (3). These polymers could be obtained only in microcrystalline form. Their structures were determined ab initio from X-ray powder diffraction data. The complex {[Ni(2)Cl(2)(bppz)(H(2)O)(2)(CH(3)OH)(2)]Cl(2)}(n)() (2) belongs to the triclinic space group P&onemacr; with a = 8.7014(4) Å, b = 10.1465(5) Å, c = 8.0303(3) Å, alpha = 116.095(2) degrees, beta = 112.713(3) degrees, gamma = 64.056(3) degrees, and Z = 1. The octahedral coordination of the nickel atom is achieved by two nitrogens of the ligand bppz, two chloride ions, and two oxygens from the solvent molecules. The bridging nature of the chloride ions and the bis-bidentate ligands (bppz) leads to a one-dimensional polymer. The compound [Cu(2)Cl(4)(bppz)](n)() (3) crystallizes in the monoclinic space group C2/m with a = 13.9124(5) Å, b = 6.1844(2) Å, c = 10.1572(3) Å, beta = 112.952(3) degrees, and Z = 2. The copper atoms display a distorted octahedral geometry where four of the coordination sites are occupied by chloride ions and the remaining two by nitrogen atoms of bppz. The metal atoms are bridged by two chlorine atoms and the bppz ligands, forming a two-dimensional coordination polymer.

Formation of Nickel(II) Coordination Polymers by a Double Betaine: [{Ni(L)(H2O) 2} n] Cl2n.2nH2O and [{Ni(L)2(H2O)2} n

Two novel polymeric nickel(II) complexes of a double betaine with a rigidtris(ethylene) bridge between the pair of nitrogen atoms, namely [ {Ni(L)(H2O)4 }n]Cl2n.2nH2O(1)and [ {Ni(L)2(H2O)2} n](ClO4)2n.4nH2O(2) [L =¯O2CCH2N+(CH2CH2)3N+CH2CO2¯], have been prepared and characterized by X-ray crystallography. Thenickel(II) atom in either complex is coordinated by unidentate carboxylategroups and aqua ligands in a distorted octahedral geometry. The crystalstructure of (1) features an infinite zigzag chain composed of an alternatearrangement of metal atoms and double betaine ligands, and hydrogen bondingamong adjacent chains leads to a three-dimensional network. Complex (2)exhibits a wave-like layer structure corresponding to the (2 0 0) family ofplanes.

Ferromagnets based on polymeric 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetrathiolato nickel and cobalt complexes

The polymeric nickel complexes 3, 5, 7, 8 and cobalt complexes 4, 6 were synthesized from the bis (tetrabutylammonium) 2,3,6,7-tetrachloronaphthalene-1,5-dithiol-4,6-dithiolate (2) or the tetrathiolate 1 and the corresponding metal-ions (Ni2+ and Co2+), using a large excess of tetrabutylammonium bromide for introducing NBu4+ as counter ion. The diamagnetic nickel coordination polymer 3 was oxidized by iodine to the paramagnetic complex 5. By exchange of the NBu4+ ion by Ni2+ and the tetrathiafulvalenium ion, respectively, the complexes 7 and 8 are obtained. The coordination polymer 7 was characterized as ferromagnetic beneath 20 K by investigating the temperature dependence of the magnetic susceptibility and the magnetization behavior. A coercive field of 1200 Oe was determined from the hysteresis loop of 7 at 4.4 K. The measured heat capacity of 7 in dependence on the temperature is in good accordance with a ferromagnetic spin ordering below 20 K. Magnetic properties comparable with those of 7 were determined for the complexes 4 and 8.

A Coordination Polymer of Nickel(II) Based on a Pentadentate N, S, and O Donor Ligand.

The synthesis, structural characterization, and electrochemical properties of a Ni(II) complex derived from the template reaction of N,N'-bis(2-mercaptoethyl)-1,5-diazacyclooctane nickel(II), Ni-1, with ICH(2)CO(2)Na are described. Blue N-(3-thiabutyl)-N'-(3-thiapentanoate)-1,5-diazacyclooctanenickel(II)iodide, [(tbtp-daco)Ni][I], [5]I, contains Ni(II) in an octahedral environment with N(2)S(2)O(2) donor atoms; one oxygen is from an adjacent [(tbtp-daco)Ni] ion and has the same distance to Ni(II) as the intramolecular oxygen, resulting in a coordination polymer. Complex [5]I.H(2)O, C(13)H(27)N(2)O(3)S(2)NiI, crystallizes in the orthorhombic space group Pbca with a = 10.898(3), b = 18.103(5), c = 19.020(5), and Z = 8. The extent to which the polymer is retained in solution is counterion dependent, which influences redox properties (accessibility of Ni(I) and Ni(III)).

Preparation and physical properties of highly conducting metal (M = Ni, Co, Cu) coordination polymers

Coordination polymers of nickel, cobalt and copper with the linking polydentate ligands tetrathiafulvalenetetrathiolate, benzene-1,2,4,5-tetrathiolate and phthalocyaninate have been prepared. The environmentally very stable materials have dc conductivities ranging between 10 −2 S·cm −1 for the polyphthalocyaninato derivatives and 10 2 S·cm −1 for the tetrathiafulvalenetetrathiolates. The temperature dependence of the dc conductivity of the latter compounds is remarkably low.

HIP technology — prospects for the 1990s

Two neutral nickel(II) coordination polymers [Ni(en)(dca)2]n (1) and [Ni(dmen)(dca)2]n (2) (en = ethylenediamine; dmen = N,N-dimethylethylenediamine; dca = dicyanamide) have been synthesized and X-ray crystallographically characterized. Each nickel(II) center in 1/2 adopts a distorted octahedral coordination environment with a NiN6 chromophore ligated by two amine N atoms of the bidentate amine (en/dmen) and four nitrile N atoms of μ1,5 bridged dca. The metal(II) centers are connected with each other through single μ1,5 M–NCNCN–M bridges, resulting in a 2D layer structure with a (4,4) topology in 1 and a 3D network of topology (6,6) in 2. Multiple lateral N–H···N and C–H···N hydrogen bondings promote dimensionality. The magnetic susceptibility results of 1 and 2 at very low temperature support the zero-field splitting effect of the nickel(II) ions.