NiII Centers Research Articles

A 3D Porous Metal Organic Framework Based on Infinite 1D Nickel(II) Chains with Rutile Topology Displaying Open Metal Sites

AbstractThe reaction of NiII with a tetra‐benzoate pyrene ligand produces a 3D porous framework based on infinite 1D NiII chains. The NiII–O connectivity and the formation of a hydroxo‐bridge (μ3‐OH) responsible for the connection of the central NiII atoms within the 1D NiII–(μ3‐OH)2–NiII chains can be straightforwardly compared with the TiIV–O–TiIV connectivity seen in TiO2. The arrangement of the TBAPy ligand around the 1D rutile‐based chains leads in the generation of a porous framework with two distinct types of pores; based on the chemistries of these two types of pores, one can be labelled as hydrophobic and the other as hydrophilic. The use of different activation methods results in the generation of either a porous framework free of guest molecules or a completely solvent‐free material, in which the terminal H2O molecules bound to NiII were removed, leading thus to a framework with open NiII sites. CO2 isotherms collected on both frameworks at 195 K and one barshowed type I isotherms characteristic of microporous materials (BET surface areas for: guest‐free framework: 257(3) m2·g–1; solvent‐free framework: 362(2) m2·g–1). The affinity of both networks at zero coverage for both CO2 and CH4 was found to be greater when the unsaturated NiII sites are available within the void space.

Concerted ligand exchange and the roles of counter anions in the reversible structural switching of crystalline peptide metallo-macrocycles.

To understand reversible structural switching in crystalline materials, we studied the mechanism of reversible crystal-to-crystal transformation of a tetranuclear Ni(II) macrocycle consisting of artificial β-dipeptides. On the basis of detailed structural analyses and thermodynamic measurements made in a comparison of pseudo-isostructural crystals (NO3 and BF4 salts), we herein discuss how ligand-exchange reactions take place in the crystal due to changes in water content and temperature. Observations of the structural transformation of NO3 salt indicated that a pseudo crystalline phase transformation takes place through concerted ligand-exchange reactions at the four Ni(II) centers of the macrocycle with hydrogen bond switching. A mechanism for this ligand exchange was supported by IR spectroscopy. Thermodynamic measurements suggested that the favorable compensation relationship of the enthalpy changes due to water uptake and structural changes are keys to the reversible structural transformation. On the basis of a comparison with the pseudo-isostructural crystals, it is apparent that the crystal packing structure and the types of counter anions are important factors for facilitating reversible ligand exchange with single crystallinity.

Synthesis, characterisation and antimicrobial activity of bis(phthalazine-1-hydrazone)-2,6-diacetylpyridine and its complexes with CoIII, NiII, CuII and ZnII

Four new complex compounds of bis(phthalazine-1-hydrazone)-2,6-diacetylpyridine (Hz2DAP) ligand with NiII, CoIII, CuII and ZnII metal centres were synthesised and characterised by single-crystal X-ray diffraction and IR spectral data. The antimicrobial activity of Hz2DAP and the obtained complexes [Co(Hz2DAP-H)Cl2]·MeOH, [Ni(Hz2DAP-H)]Cl·MeOH, [Cu(Hz2DAP-H)Cl] and [Zn(Hz2DAP-2H)]·H2O were tested in vitro against selected Gram(−) and Gram(+) bacterial strains and fungi. The antimicrobial activity of the ligand is negligible, while its complexes with NiII, CoIII and CuII show considerable activity against Escherichia coli, Staphylococcus aureus and Micrococcus lysodeikticus. On the contrary, [Zn(Hz2DAP-2H)]·H2O promotes the growth of Candida albicans, while its antibacterial activity is negligible. On the basis of thermal data and those from coupled TG/MS measurements the decomposition mechanisms were determined and evaluated.

Anion controlled structural and magnetic diversity in unusual mixed-bridged polynuclear Ni(II) complexes with a versatile bis(2-methoxy phenol)diamine hexadentate ligand. An experimental and theoretical magneto-structural study.

This work reports the syntheses, crystal structures, magnetic properties and DFT calculations of six novel polynuclear NiII compounds [Ni2(μ-HL1)2(μ-N3)]N3·(CH3OH)2·2H2O (1), [Ni2(μ-HL1)2(μ-N3)][Na2Ni2(μ-L1)2(μ-N3)2(CH3OH)(N3)]·4CH3OH (2), [Ni4(μ-L1)2(μ-N3)4(CH3OH)2]·2CH3OH (3), [Na2Ni4(μ-L1)2(μ-OAc)2(μ-N3)4(CH3OH)4]·2CH3OH (4), [Ni4(μ-L1)2(μ-Cl)2(Cl)2] (5), and [Ni3(μ-L1)2(acac)2(H2O)2] (6), with uncommon structures and rare mixed-bridges between NiII ions, which were prepared from the versatile polytopic Mannich base ligand N,N′-dimethyl-N,N′-bis(2-hydroxy-3-methoxy-5-methylbenzyl)ethylenediamine (H2L1). The anionic coligand (azide, chloride, acetate and acetylacetonate) and reaction conditions play crucial roles in determining the final structure of these compounds and consequently their magnetic properties. Compound 1 contains a Ni2 cationic unit with rare di-μ-phenoxido/μ1,1-azide triple mixed bridges whereas complex 2 is made from the same Ni2 cationic unit as 1, cocrystallized with Na2Ni2 neutral units, in which double μ1,1,1-azide bridges connect the NiII and NaI anions. Complexes 3 and 4 are Ni4 complexes with defective dicubane and linear structures, respectively. Complex 3 has two distinct types of mixed bridges, μ-phenoxido/μ1,1,1-azido and μ1,1-azido/μ1,1,1-azido and a double di-μ1,1,1-azido bridge, the latter connecting the face-sharing NiII ions. In 4, rare μ-phenoxido/μ1,1-azide/syn–syn acetate triple mixed bridges connect central and terminal NiII atoms whereas a double μ1,1-azide planar bridging fragment links the central NiII ions. Complex 5 has a defective-dicubane structure with double μ-phenoxido/μ3-chloro mixed bridges and di-μ3-chloro bridges, whereas complex 6 has a bent structure with very uncommon single μ-phenoxido bridges. The analysis of the magnetic properties reveals that in complexes 1–4 all magnetic pathways transmit ferromagnetic interactions leading to S = 2 ground states for 1 and 2 and S = 4 ground states for 3 and 4. In complex 5, the double μ-phenoxido/μ3-chloro mixed bridges and di-μ3-chloro bridges mediate antiferro- and ferromagnetic interactions, respectively, giving rise to a S = 0 ground state. Complex 6 shows antiferromagnetic interactions between the NiII ions through single μ-phenoxido bridging groups, leading to an S = 1 ground state. DFT calculations on the X-ray structures and model compounds were performed to support the magneto-structural data of the above compounds.

Proton-controlled formation and interconversion of AuI2NiII trinuclear and AuI4NiII3 heptanuclear complexes with mixed thiomalate and bis(diphenylphosphino)ethane

Treatment of a newly prepared digold(i) complex, [Au2(dppe)(H2msa)2] ([H41]; dppe = 1,2-bis(diphenylphosphino)ethane, msa = thiomalate), with Ni(2+) gave two interconvertible multinuclear complexes, [Ni{Au2(dppe)(msa)2}](2-) ([2](2-)) and [Ni3{Au2(dppe)(Hmsa)2}{Au2(dppe)(msa)2}(MeOH)3] ([3]), dependent on solution acidities.

Solvent‐Dependent Reversible Ligand Exchange in Nickel Complexes of a Monosulfide Bis(diphenylphosphino)(N‐thioether)amine

The coordination chemistry of the DPPA-type functional phosphine bis(diphenylphosphino)(N-thioether)amine N(PPh2)2(CH2)3SMe () and its monosulfide derivative, (Ph2P)N{P(S)Ph2}(CH2)3SMe (1·S), towards Ni(II) precursors has been investigated. The crystal structures of N{P(S)Ph2}2(CH2)3SMe (1·S2), [NiCl2{(Ph2P)2N(CH2)3SMe-P,P}] (2), [NiCl2((Ph2P)N{P(S)Ph2}(CH2)3SMe-P,S)] (3), [Ni((Ph2P)N{P(S)Ph2}(CH2)3SMe-P,S)2]NiCl4 (3'), [Ni((Ph2P)N{P(S)Ph2}(CH2)3SMe-P,S)2](BF4)2 (4), and [Ni((Ph2P)NH{P(S)Ph2}-P,S)2]Cl2 (5) have been determined by single-crystal X-ray diffraction. In all of the complexes with the hybrid ligand 1·S, P,S-chelation to the Ni(II) center is observed. Despite the stability generally associated with five-membered ring chelation, easy migration of this LL'-type P,S-chelating ligand from one metal center to another was observed, which accounts for the reversible ligand-redistribution reaction occurring in the equilibrium between the neutral, diamagnetic complex [NiCl2LL'] and the paramagnetic ion-pair [Ni(LL')2][NiCl4]. Detailed investigations by multinuclear NMR, UV/Vis, and FTIR spectroscopic methods and DFT calculations are reported. Each of the formula isomers 3 and 3' can be selectively obtained, depending on the experimental conditions.

Dinuclear and heptanuclear nickel(II) complexes: Anion coordination induced ligand arm hydrolysis and aggregation around a nickel(II) core

The heptanuclear and tetracationic nickel(II) complex [Ni7(μ3-OH)6(μ3-H2L)4](NO3)4·2MeOH (3·2MeOH); (H3L is 2,6-bis-[(3-hydroxy-propylimino)-methyl]-4-methyl-phenol), featuring four defective cubanes around a pivotal nickel(II) ion, has been obtained via hydroxido-bridge-induced assemblage of two Ni3 fragments. Presence of azido (N3−) and bromido (Br−) ions in reactions on the contrary lead to one ligand imine arm hydrolysis and formations of [Ni2(N3)2(μ-HL1)2(OH2)2] (1) and [Ni2Br2(μ-HL1)2(OH2)2] (2); where H2L1 is 2-hydroxy-3-[(3-hydroxy-propylimino)-methyl]-5-methyl-benzaldehyde. X-ray structural analyses of 3 show six symmetrically positioned NiII around a central NiII and bridged by six in situ generated hydroxido groups from solvent water molecules. Density functional theory (DFT) calculations have also been performed to predict magnetic behavior of the complexes. The spin density surface of compounds 1 and 2 has been also obtained.

ChemInform Abstract: [NiCl2(dppp)]‐Catalyzed Cross‐Coupling of Aryl Halides with Dialkyl Phosphite, Diphenylphosphine Oxide, and Diphenylphosphine.

We present a general approach to C?P bond formation through the cross-coupling of aryl halides with a dialkyl phosphite, diphenylphosphine oxide, and diphenylphosphane by using [NiCl2(dppp)] as catalyst (dppp=1,3-bis(diphenylphosphino)propane). This catalyst system displays a broad applicability that is capable of catalyzing the cross-coupling of aryl bromides, particularly a range of unreactive aryl chlorides, with various types of phosphorus substrates, such as a dialkyl phosphite, diphenylphosphine oxide, and diphenylphosphane. Consequently, the synthesis of valuable phosphonates, phosphine oxides, and phosphanes can be achieved with one catalyst system. Moreover, the reaction proceeds not only at a much lower temperature (100120?degrees C) relative to the classic Arbuzov reaction (ca. 160220?degrees C), but also without the need of external reductants and supporting ligands. In addition, owing to the relatively mild reaction conditions, a range of labile groups, such as ether, ester, ketone, and cyano groups, are tolerated. Finally, a brief mechanistic study revealed that by using [NiCl2(dppp)] as a catalyst, the NiII center could be readily reduced in situ to Ni0 by the phosphorus substrates due to the influence of the dppp ligand, thereby facilitating the oxidative addition of aryl halides to a Ni0 center. This step is the key to bringing the reaction into the catalytic cycle.

Two distinct tetranuclear motifs, rectangular vs. extended, are observed for complexes of a bis-tetradentate pyrimidine-based ligand

The 1 : 2 reactions of 4,6-bis[N,N-bis(2′-pyridylmethyl)aminomethyl]-2-phenylpyrimidine (LMe) and MnII, CoII, NiII and CuII chloride salts in MeOH gave the tetranuclear complexes [MnII4(LMe)2Cl8]·2H2O (1), CoII4(LMe)2Cl8·10H2O (2), [Ni4II(LMe)2Cl4]Cl4·8H2O (3) and [CuII4(LMe)2Cl6]Cl2·8H2O (4), respectively. X-ray crystal structure determinations carried out on three of the complexes revealed that in the case of NiII (3′) the LMe ligand is bound in the expected bis-tetradentate fashion, bridging the encapsulated pair of NiII centers via the pyrimidine ring, and that two pairs of chloride anions bridge a pair of such dimetallic units, affording a closed rectangular tetranuclear core overall. In contrast, in the case of MnII (1′) and CuII (4′) only one binding pocket of the LMe ligand strand binds in the expected tetradentate manner, whilst the other binds in a terdentate manner as one pyrimidine nitrogen atom does not bind, so in these cases the pyrimidine moiety does not bridge the metal centres, resulting instead in ‘extended’, linear tetranuclear assemblies.

Complexes of a porphyrin-like N4-donor Schiff-base macrocycle

A metal-free 16-membered N4-donor [1 + 1] Schiff-base macrocycle was isolated as HL(Pr)·2acid, by 1 : 1 condensation of diphenylamine-2,2'-dicarboxaldehyde (1), dipropylene triamine and an excess of either acetic or formic acid, or as HL(Pr)·(tosylic acid) when just one equivalent of tosylic acid was employed. Interestingly, the acid-free synthesis employed for the 14-membered analogue HL(Et) failed to generate pure HL(Pr) macrocycle, but nevertheless the crude product obtained was able to be used in subsequent complexation reactions to form five mononuclear complexes: Zn(II)L(Pr)(BF4)·H2O·0.5IPA (where IPA is isopropylalcohol), [Cu(II)L(Pr)](BF4), [Ni(II)L(Pr)](BF4), [Co(II)L(Pr)](BF4)·0.5H2O, [Fe(III)L(Pr)(NCS)2]·1.5H2O. Crystal structure determinations show that, like the HL(Et) analogues, [Ni(II)L(Pr)](BF4) features a square planar N4 coordinated Ni(II) centre and [Fe(III)L(Pr)(NCS)2]·0.15MeOH·0.2H2O features an octahedral N6 coordinated Fe(III) centre (two NCS anions bound axially). In both cases the N4-donor macrocycle is bound equatorially to the metal ion. Cyclic voltammograms of the BF4 complexes were carried out in MeCN vs. 0.01 mol L(-1) AgNO3/Ag and revealed multiple redox processes. The Zn(II) complex exhibits multiple ligand-centered redox processes. Interestingly, [Ni(II)L(Pr)](BF4) has two reversible redox processes, at E(m) = +0.38 (ΔE = 0.06 V) and -1.7 V (ΔE = 0.06 V), whereas the previously reported analogue [Ni(II)L(Et)](BF4) had a process at E(pc) = +0.59 V with only a weak return wave. Likewise, [Cu(II)L(Pr)](BF4) has a reversible process, at E(m) = -1.17 V (ΔE = 0.06 V) plus a process at E(pc) = +0.45 V, whereas previously reported [Cu(II)L(Et)](BF4) only featured irreversible processes, with the oxidation occurring at E(pc) = +0.50 V.

A Heterobimetallic Approach To Stabilize the Elusive Disulfur Radical Trianion (“Subsulfide”) ${{\rm S}{{{{\bullet}}3- \hfill \atop 2\hfill}}}$

A unique heterobimetallic disulfur monoradical, complex 2, with a diamond-shaped {NiS(2)Pt} core has been synthesized by two-electron reduction of a supersulfido-(nacnac)nickel(II) complex (nacnac=β-diketiminato) with [Pt(Ph(3)P)(2)(η(2)-C(2)H(4))] as a platinum(0) source and isolated in 82% yield. Strikingly, the results of DFT calculations in accordance with spectroscopic (EPR, paramagnetic NMR) and structural features of the complex revealed that the bonding situation of the S(2) ligand is between the elusive "half-bonded" S(2) radical trianion (S2(·3-)) and two separated S(2-) ligands and two separated S(2-) ligands. Accordingly, the Ni(II) center is partially oxidized, whereas the Pt(II) site is redox innocent. The complex can be reversibly oxidized to the corresponding Ni,Pt-disulfido monocation, compound 3, with a S--S single bond, and reacts readily with O(2) to form the corresponding superoxonickel(II) and disulfidoplatinum(II) (4) complexes. These compounds have been isolated in crystalline form and fully characterized, including IR and multi-nuclear NMR spectroscopy as well as ESI mass spectrometry. The molecular structures of compounds 2-4 have been confirmed by single-crystal X-ray crystallography.

Syntheses, Structures, and Magnetic Properties of a Novel mer-[(bbp)FeIII(CN)3]2– Building Block (bbp: bis(2-benzimidazolyl)pyridine dianion) and Its Related Heterobimetallic Fe(III)–Ni(II) Complexes

A new symmetrical tricyanide building block mer-[Fe(bbp)(CN)3](2-) [1; bbp = bis(2-benzimidazolyl)pyridine dianion] has been prepared and structurally and magnetically characterized. It forms a new low-spin meridionally capped {Fe(III)L(CN)3} fragment with the tridentate bbp ligand. The reaction of 1 with Ni(II) salts in the presence of various ancillary ligands affords several new cyanido-bridged complexes: a trinuclear complex {[Ni(ntb)(MeOH)]2[Fe(bbp)(CN)3][ClO4]2}·2MeOH (2), a tetranuclear compound {[Ni(tren)]2[Fe(bbp)(CN)3]2}·7MeOH (3), and a one-dimensional heterobimetallic system: {[Ni(dpd)2]2[Fe(bbp)(CN)3]2}·9MeOH·3H2O (4) [ntb = tris(2-benzimidazolylmethyl)amine, tren = tris(2-aminoethyl)amine, and dpd = 2,2-dimethyl-1,3-propanediamine]. The structural data shows that 2 is a linear complex in which a central Fe(III) ion links two adjacent Ni(II) ions via axial cyanides, while 3 is a molecular square that contains cyanido-bridged Ni(II) and Fe(III) ions at alternate corners. Complex 4 is a one-dimensional system that is composed of alternating cyanido-bridged Ni(II) and Fe(III) centers. Compounds 2-4 display extensive hydrogen bonding and moderately strong π-π stacking interactions in the solid state. Magnetic studies show that ferromagnetic exchange is operative within the Fe(III)LS(μ-CN)Ni(II) units of 2-4.

{2,6-Bis[(2,6-diisopropylphosphanyl)oxy]-4-fluorophenyl-κ3P,C1,P′}(1H-pyrazole-κN2)nickel(II) hexafluorophosphate

The title compound, [Ni(C18H30FO2P2)(C3H4N2)]PF6, was prepared by halide abstraction with TlPF6 in the presence of CH3CN in CDCl3 from the respective neutral pincer chlorido analogue followed by addition of pyrazole. The PO—C—OP pincer ligand acts in typical trans-P2 tridentate fashion to generate a distorted square-planar nickel structure. The Ni—N(pyrazole) distance is 1.925 (2) Å and the plane of the pyrazole ligand is rotated 56.2 (1)° relative to the approximate square plane surrounding the NiII center in which the pyrazole is bound to the NiII atom through its sp 2-hybridized N atom. This Ni—N distance is similar to bond lengths in the other reported NiII pincer-ligand square-planar pyrazole complex structures; however, its dihedral angle is significantly larger than any of those for the latter set of pyrazole complexes.

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

AbstractTwo dinuclear succinato‐bridged nickel(II) complexes [Ni(RR‐L)]2(μ‐SA)(ClO4)2 (1) and [Ni(SS‐L)]2(μ‐SA)(ClO4)2 (2) (L = 5, 5, 7, 12, 12, 14‐hexamethyl‐1, 4, 8, 11‐tetraazacyclotetradecane, SA = succinic acid) were synthesized and characterized by EA, Circular dichroism (CD), as well as IR and UV/Vis spectroscopy. Single crystal X‐ray diffraction analyses revealed that the NiII atoms display a distorted octahedral coordination arrangement, and the succinato ligand bridges two central NiII atoms in a bis bidentate fashion to form dimers in 1 and 2. The monomers of {[Ni(RR‐L)]2(μ‐SA)}2+ and {[Ni(SS‐L)]2(μ‐SA)}2+ are connected by O–H···O and N–H···O hydrogen bonds into a 1D right‐handed and left‐handed helical chain along the b axis, respectively. The homochiral natures of 1 and 2 are confirmed by the results of CD spectroscopy.

End-to-end thiocyanato-bridged zig-zag polymers of CuII, CoII and NiII with a hydrazone ligand: EPR, magnetic susceptibility and biological study

The reactions of a tridentate hydrazone ligand, N′-[1-(pyridin-2-yl)ethylidene]acetohydrazide (LH), derived from condensation of 2-acetylpyridine with acetic hydrazide, with M(NO3)2·nH2O [M=Cu, Co and Ni] in the presence of thiocyanate afford three end-to-end zig-zag coordination polymers, [CuLH(NO3)(μ1,3-NCS)]n·nH2O (1), [CoLH(NCS)(μ1,3-NCS)]n (2) and [NiLH(NCS)(μ1,3-NCS)]n (3) (where LH=CH3C(O)–N–NCCH3C5H4N). Single-crystal X-ray structural determination studies reveal that in all the complexes, the hydrazone ligand in the neutral keto form (LH) coordinates a MII ion that is bridged to two neighboring metal centers by SCN− anions, generating a 1-D helical coordination chain. In 1, the CuII atom adopts a distorted tetragonal bipyramid geometry whereas in 2 and 3, the central CoII or NiII atom possesses into a distorted octahedral environment. All the aforementioned compounds have been fully characterized by elemental analysis, IR, UV–Vis and EPR spectra. Variable temperature magnetic susceptibility measurement of 1 accounts the weak antiferromagnetic interactions whereas 2 shows single-ion anisotropy. Compound 3 is well described as a 3-D ferromagnetic. The inhibitory effects of all the complexes on the cell population growth of human lung carcinoma cells (A549 cells), human colorectal carcinoma cells (COLO 205 cells and HT-29 cells), and human hepatocellular carcinoma cells (PLC5 cells) were determined by MTT assays.

Two Supramolecular Nickel(II) Complexes: Syntheses, Crystal Structures and Solvent Effects

AbstractTwo nickel(II) complexes, namely {[NiL(MeOH)(μ‐OAc)]2Ni}·2CH2Cl2·2MeOH (1) and {[NiL(EtOH)(μ‐OAc)]2Ni}·2EtOH (2) {H2L = 5, 5′‐dimethoxy‐2, 2′‐[(ethylene)dioxybis(nitrilomethylidyne)]diphenol}, were synthesized and structurally characterized. Two trinuclear NiII complexes are both hexacoordinate around the central NiII atoms, showing octahedral coordination arrangements, and each complex comprises three divalent NiII atoms, two deprotonated L2– ligands, in which four μ‐phenoxo oxygen atoms forming two [NiL(X)] (X = MeOH or EtOH) units, and coordinated and non‐coordinated solvent molecules. Complex 1 exhibits a 2D supramolecular network through intermolecular O–H···O, C–H···O and C–H···π interactions, whereas complex 2 forms an infinite 1D chain by intermolecular C–H···O hydrogen bonding interactions.

Bis(methanol-1κO)tetra-μ-pyridazine-1:2κ4N:N′;2:3κ4N:N′-di-μ-thiocyanato-1:2κ2N:N;2:3κ2N:N-tetrathiocyanato-1κ2N,3κ2N-trinickel(II) methanol tetrasolvate

Reaction of an excess nickel(II) thio­cyanate with pyridazine leads to single crystals of the title compound, [Ni3(NCS)6(N2C4H4)4(CH3OH)2]·4CH3OH. The crystal structure consists of trimeric discrete complexes, in which two NiII cations are coordinated by two terminal and one μ-1,1 bridging thio­cyanato anions, one methanol mol­ecule and two bridging pyridazine ligands, whereas the central NiII atom is coordinated by two μ-1,1 bridging anions as well as four bridging pyridazine ligands. The asymmetric unit consists of two crystallographically independent Ni cations, one of which is located on a center of inversion, as well as three crystallographically independent thio­cyanato anions, two pyridazine ligands and three independent methanol mol­ecules in general positions. Two of the solvent mol­ecules do not coordinate to the metal atoms and are located in cavities of the structure. The discrete complexes are linked by inter­molecular O—H⋯O and O—H⋯S hydrogen bonding into layers parallel to the bc plane.

Tris(5,6-dimethyl-1H-benzimidazole-κN 3)(pyridine-2,6-dicarboxylato-κ3 O 2,N,O 6)nickel(II)

The title mononuclear complex, [Ni(C7H3NO4)(C9H10N2)3], shows a central NiII atom which is coordinated by two carboxyl­ate O atoms and the N atom from a pyridine-2,6-dicarboxyl­ate ligand and by three N atoms from different 5,6-dimethyl-1H-­benzimidazole ligands in a distorted octa­hedral geometry. The crystal structure shows intermolecular N—H⋯O hydrogen bonds.

Bis[μ-N′-(adamantan-1-ylcarbonyl)-2-oxidobenzohydrazidato(3−)]tetrapyridinetrinickel(II) dimethylformamide monosolvate monohydrate

In the title trinuclear NiII compound, [Ni3(C18H19N2O3)2(C5H5N)4]·C3H7NO·H2O, three NiII cations are bridged by two N′-(adamantan-1-ylcarbon­yl)-2-oxidobenzohydrazidate trianions. The central NiII cation has a distorted octa­hedral N4O2 coordination environment where a reverse torsion occurs between the two bridging ligands, whereas the two NiII cations on the sides each adopt an N2O2 square-planar coordination. Weak intra­molecular C—H⋯O and C—H⋯N inter­actions help to stabilize the mol­ecular structure. In the crystal, the lattice water mol­ecule links with the NiII complex and dimethyl­formamide solvent mol­ecule via O—H⋯O hydrogen bonding.

{S-Benzyl 3-[(6-methylpyridin-2-yl)methylidene]dithiocarbazato}nickel(II) monohydrate

The structure of the title compound, [Ni(C15H14N3S2)2]·H2O, has one mol­ecule in the asymmetric unit, along with a solvent water mol­ecule. The two different Schiff base moieties coordinate to the central NiII ion as tridentate N,N′,S-chelating ligands, creating a six-coordinate distorted octa­hedral environment [the smallest angle being 77.43 (7)° and the widest angle being 169.99 (7)°]. The mean planes of the two ligands are nearly orthogonal to each other with an angle of 89.53 (6)°. The packing of the complex is supported by O—H⋯N and O—H⋯S hydrogen bonding between the solvent water mol­ecule and the uncoordinated N and S atoms of neighbouring ligands.