Dinuclear Ni2 Research Articles

Atomically Precise Dinuclear Ni2 Active Site-Modified MOF-Derived ZnO@NC Heterojunction toward High-Performance N2 Photofixation

The development of heterogeneous catalysts with atom-dispersed active sites is essential to facilitate nitrogen (N2) activation for the N2 reduction reaction (NRR). However, it remains a major challenge to tune the coordination configuration of the metal centers to further accelerate the activation kinetics. Herein, an atomically precise dinuclear Ni2 site-modified metal–organic framework (MOF)-derived ZnO@NC heterojunction (ZnO@NC-Ni2) was developed for effective N2 photofixation under mild conditions. Moreover, advanced structural characterization indicates that the most active N-coordinated bimetallic site configurations are Ni2–N6, where two Ni1–N4 moieties are shared with two N atoms. Theoretical calculations further demonstrate that the binuclear Ni2 active sites of ZnO@NC-Ni2 could adjust the N2 adsorption configuration as the side-on bridging adsorption mode (denoted as “*N≡N*”), while the single metal Ni1 sites of ZnO@NC-Ni1 tend to form a terminal adsorption configuration with N2 (“*N≡N” type). As a result, the unique electronic structure of binuclear Ni2 active sites in ZnO@NC-Ni2 tends to proceed as an associative alternating pathway, thereby decreasing the activation energy barrier of the reaction procedure and favoring the photocatalytic NRR. The present study provides a perspective to probe the relationship between the coordination architecture of earth-abundant metal active centers and NRR activities.

Atomically Precise Dinuclear Site Active toward Electrocatalytic CO2 Reduction.

The development of atomically precise dinuclear heterogeneous catalysts is promising to achieve efficient catalytic performance and is also helpful to the atomic-level understanding on the synergy mechanism under reaction conditions. Here, we report a Ni2(dppm)2Cl3 dinuclear-cluster-derived strategy to a uniform atomically precise Ni2 site, consisting of two Ni1-N4 moieties shared with two nitrogen atoms, anchored on a N-doped carbon. By using operando synchrotron X-ray absorption spectroscopy, we identify the dynamically catalytic dinuclear Ni2 structure under electrochemical CO2 reduction reaction, revealing an oxygen-bridge adsorption on the Ni2-N6 site to form an O-Ni2-N6 structure with enhanced Ni-Ni interaction. Theoretical simulations demonstrate that the key O-Ni2-N6 structure can significantly lower the energy barrier for CO2 activation. As a result, the dinuclear Ni2 catalyst exhibits >94% Faradaic efficiency for efficient carbon monoxide production. This work provides bottom-up target synthesis approaches and evidences the identity of dinuclear sites active toward catalytic reactions.

Nickel(II)–Nickel(II) Azadithiolates: Synthesis, Structural Characterization, and Electrocatalytic H2 Production

Azadithiolato-bridged dinuclear Ni2 complexes with the general formula [(η5-C5H5)Ni{(μ-SCH2)2NC6H4R-4}Ni(diphos)]BF4 (8–11, R = H, Cl, MeO; diphos = dppv, dppe) have been prepared by a well-designe...

2‐Acetyloxymethyl‐substituted 5,6,7‐trihydroquinolinyl‐8‐ylideneamine‐Ni(II) chlorides and their application in ethylene dimerization/trimerization

AbstractSix examples of 2‐acetyloxymethyl‐substituted 5,6,7‐trihydroquinolinyl‐8‐ylideneamine‐nickel(II) chlorides, [2‐(CH2OC(O)Me)‐8‐{N(Ar)}C9H8N]NiCl2 (Ar = 2,6‐Me2C6H3 Ni1, 2,6‐Et2C6H3 Ni2, 2,6‐i‐Pr2C6H3 Ni3, 2,4,6‐Me3C6H2 Ni4, 2,6‐Et2–4‐MeC6H2 Ni5, 2,4,6‐t‐Bu3C6H2 Ni6), have been prepared by a one‐pot template reaction of 2‐(hydroxymethyl)‐6,7‐dihydroquinolin‐8(5H)‐one with nickel dichloride hexahydrate, the corresponding aniline and acetic acid. All complexes were characterized by elemental analysis and IR spectroscopy, while dinuclear Ni2 and mononuclear Ni3·OH2 have additionally been the subject of single crystal X‐ray diffraction studies; in both structures the acetyloxymethyl group remained uncoordinated. On activationof Ni1 – Ni6 with MMAO, hexenes (C6: ca. 48% 1‐hexene) formed the major product of ethylene oligomerization along with minor quantities of butenes (C4); high overall activities of up to 1.33 × 106 g·mol–1 (Ni)h–1 (for mesityl‐containing Ni4) were achieved at 30 oCand 10 atm C2H4. By comparison with MAO as co‐catalyst, Ni1 – Ni6 exhibited lower activities but displayed a specificity towards ethylene dimerization (C4: 64–99% 1‐butene). Furthermore, sizable induction periods were a feature of the MAO runs with Ni1/MAO reaching peak catalytic activity only after 45 mins.

Syntheses, structures and magnetic properties of nine coordination polymers based on terphenyl-tetracarboxylic acid ligands.

Nine coordination polymers (CPs) [Mn(H3L)(H2L)0.5(phen)]n (1), [Ni2L(phen)2(μ2-H2O)]n (2), {[Mn2L(phen)2]·(DMA)(H2O)}n (3), {[Co2L(μ2-H2O)(μ2-DMA)]·DMF}n (4), [CoL0.5(H2O)(phen)]n (5), {[Ni2L(μ2-H2O)(μ2-DMA)]·DMA}n (6), {[Co2L(μ2-H2O)(μ2-DMA)]·DMA}n (7), {[Ni2L(μ2-H2O)(H2O)2(DMF)2]·(H2O)2(DMF)}n (8), and {[Ni4L2(μ2-H2O)4(H2O)2]·(H2O)2(NMP)}n (9) (H4L = 1,1':4',1''-terphenyl-2',4,4'',5'-tetracarboxylic acid, DMA = N,N-dimethylacetamine, DMF = N,N-dimethylformamide, NMP = N-methyl-2-pyrrolidone, phen = 1,10-phenanthroline) have been synthesized and structurally characterized. Crystal structural analyses reveal that 1 features the uninodal 2D (4,4) network with the dinuclear Mn2(COO)2 units as 4-connected nodes. 3 and 5 possess the binodal 2D (4,4) network with dinuclear Mn2(COO)4/Co2O2 units and L4- ligands as 4-connected nodes, respectively. In 2 and 8, each dinuclear Ni2(COO)2(μ2-H2O) unit links to four L4- ligands and each L4- ligand bridges four dinuclear Ni2(COO)2(μ2-H2O) units to generate the 3D framework, which can also be rationalized as a binodal 4,4-connected (42·84)(42·84) topological network by considering the dinuclear Ni2(COO)2(μ2-H2O) units as non-planar 4-connected nodes and L4- ligands as planar 4-connected nodes, respectively. In 4, 6-7 and 9, there exist a series of parallel-aligned metal-carboxylate chains, which are linked along two directions by para-terphenyl moieties of L4- ligands to generate the 3D frameworks. Moreover, direct current magnetic susceptibility measurements were carried out to study their magnetic properties. In complexes 2 and 9, weak ferromagnetic interactions between the magnetic centers were observed. In addition, the other compounds show weak antiferromagnetic exchange interactions between the adjacent metal ions.

Reactions of dinuclear Ni2complexes [Ni(RNPyS4)]2(RNPyS4= 2,6-bis(2-mercaptophenylthiomethyl)-4-R-pyridine) with Fe(CO)3(BDA) (BDA = benzylidene acetone) leading to heterodinuclear NiFe and mononuclear Fe complexes related to the active sites of [NiFe]- and [Fe]-hydrogenases

While the parent Ni2 complex [Ni(RNPyS4)]2 (1a, R = H; RNPyS4 = 2,6-bis(2-mercaptophenylthiomethyl)-4-R-pyridine) cannot react with Fe(CO)3(BDA) in THF at room temperature, its substituted derivatives (1b, R = MeO; 1c, Cl; 1d, Br; 1e, i-Pr; 1f, BzO; 1g, MeS) have been found to react with Fe(CO)3(BDA) under the same conditions to give the first [RNPyS4] ligand-containing heterodinuclear [NiFe]-hydrogenase model complexes NiFe(RNPyS4)(CO)3 (2b, R = MeO; 2c, Cl; 2d, Br; 2e, i-Pr; 2f, BzO; 2g, MeS) along with the mononuclear [Fe]-hydrogenase model complexes Fe(RNPyS4)(CO) (3b, R = MeO; 3c, Cl; 3d, Br; 3e, i-Pr; 3f, BzO; 3g, MeS). However, when Ni2 complexes 1a–1g react with Fe(CO)3(BDA) in THF at the higher temperature of 40 °C, only the mononuclear complexes 3a–3g are obtained without the corresponding dinuclear complexes 2a–2g being isolated. While all the new complexes are characterized by elemental analysis and spectroscopy, the molecular structures of 1f, 2c, 3f and 3g have been further confirmed by X-ray crystallography. In addition, a possible pathway for the formation of 2a–2g and 3a–3g is suggested, which has been proved by monitoring the reaction course of dinuclear Ni2 complex 1e with Fe(CO)3(BDA) using in situ IR spectroscopy.

An experimental and theoretical magneto-structural study of polynuclear Ni(II) complexes assembled from a versatile bis(salicylaldehyde)diamine polytopic ligand.

Six novel Ni(II) complexes, ranging from mononuclear to tetranuclear, have been prepared from the polytopic symmetrical Mannich base ligand N,N'-dimethyl-N,N'-bis(2-hidroxy-3-formyl-5-bromo-benzyl)ethylenediamine (H2L) and different anionic coligands: [Ni(H2L)(NO3)(H2O)]NO3·H2O (), [Ni2(μ-L)(acac)2(H2O)]·CH3CN (), [Ni2(μ-L)(μ-OAc)(NCS)] (), [Ni3(μ-L)2(μ-OH2)2(H2O)(CH3CN)](NO3)2·4CH3CN (), [Ni4(μ-L)2(μ-OAc)2(μ-OCH3)2]·6H2O·2CH3OH () and [Ni4(μ-L)2(μ-OAc)2(μ-N3)2]·2H2O·CH3OH (). These complexes have been characterized by single crystal X-ray diffraction, magnetic measurements and DFT theoretical calculations. The structural analysis of these complexes reveals that the anionic coligand and reaction conditions play a fundamental role in determining their final structures and magnetic properties. Compound contains a monomeric cationic unit with the nickel ion coordinated in the external O4 site of the compartmental ligand H2L, which acts in a neutral zwitterionic form. Complexes and are dinuclear Ni2 neutral entities, in which the Ni(II) ions are connected through two μ-phenoxido bridging groups. The Ni(O)2Ni bridging fragment in is almost planar, whereas in is bent due to the additional presence of a syn-syn acetate bridge connecting the Ni(II) atoms. Complex has a bent trinuclear structure with double μ-phenoxido/μ-water bridges between the central and terminal nickel atoms. Complexes and are Ni4 complexes with defective dicubane structures, in which triple μ-phenoxido/μ1,1,1-X/syn-syn acetate and double μ-phenoxido/μ1,1,1-X mixed bridges connect central and terminal Ni(II) atoms, whereas double μ1,1,1-X bridging ligands link the central Ni(II) ions (X = methoxido and azido groups for and , respectively). Magnetic susceptibility measurements reveal that complex shows a moderate antiferromagnetic interaction between the Ni(II) ions through the double di-μ-phenoxido bridge, leading to a S = 0 ground state. Compared to , complex shows a much weaker magnetic exchange interaction due the counter-complementarity effect provoked by the additional presence of the syn-syn acetate bridging group, as well as the non-planarity of the bridging fragment. In complex , the double μ-phenoxido/μ-water mixed bridges lead to very weak antiferromagnetic interactions between the central and external Ni(II) ions. Overall ferromagnetic interactions are found for , and , although in not all the magnetic pathways transmit ferromagnetic interactions. A detailed analysis of the magnetic exchange interactions transmitted through the different pathways as well as DFT calculations on the X-ray structures of compounds were performed to support the magneto-structural data of these compounds.

Infrared photodissociation spectra of mass selected homoleptic nickel carbonyl cluster cations in the gas phase

Infrared spectra of mass-selected homoleptic nickel carbonyl cluster cations including dinuclear Ni2(CO)7(+) and Ni2(CO)8(+), trinuclear Ni3(CO)9(+) and tetranuclear Ni4(CO)11(+) are measured via infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The structures are established by comparison of the experimental spectra with simulated spectra derived from density functional calculations. The Ni2(CO)7(+) cation is characterized to have an unbridged asymmetric (OC)4Ni-Ni(CO)3(+) structure with a Ni-Ni single bond. The Ni2(CO)8(+) cation has a Ni-Ni half-bonded D3d structure with both nickel centers exhibiting an 18-electron configuration. The trinuclear Ni3(CO)9(+) cluster cation is determined to have an open chain like (OC)4Ni-NiCO-Ni(CO)4 structure. The tetranuclear Ni4(CO)11(+) cluster cation is determined to have a tetrahedral structure with two-center and three-center bridge-bonded carbonyl units. These nickel carbonyl cluster cations all involve trigonal pyramid like Ni(CO)4 building blocks that satisfy the 18-electron configuration of the nickel centers.

Enhanced ferromagnetic interaction in metallacyclic complexes incorporating m-phenylenediamidato bridges.

The double stranded Cu(II)2-metallacyclic complex of formula [Cu2(mbpb)2].2H2O (1) and the triple stranded Ni(II)2-metallacyclic complexes of formula [Ni2(Hmbpb)3]PF6.21H2O (2), [Co(H2O)6][Ni2(mbpb)3)]THF.10H2O (3) and {Ag2(H2O)[Ni2(mbpb)3]}.11H2O (4) (where H2mbpb is the bisbidentate dinucleating bridging ligand 1,3-bis(pyridine-2-carboxamide) benzene) have been synthesised and characterised by single-crystal X-ray diffraction. Within the dinuclear molecules, metal ions are bridged by either fully or semideprotonated bisbidentate ligands, which are coordinated through the pyridine and amidato nitrogen donor atoms. In complex 4 the triple stranded dinuclear Ni2 units are connected to the Ag+ cations through O-amidato bridges and Ag-pi(benzene) interactions to afford a 1D bimetallic chain. Cu2 (1) and Ni2 (2-4) complexes exhibit ferromagnetic coupling between the metal ions through the bridging ligand with J(Cu-Cu) = 21.1 cm(-1) and J(Ni-Ni) in the range of 2.9-3.6 cm(-1), respectively. Amongst copper(II) dinuclear complexes bearing m-phenylenediamidato bridges, complex 1 exhibits the stronger ferromagnetic exchange coupling reported so far. DFT calculations firstly confirm that the spin polarisation mechanism is responsible for the ferromagnetic coupling, and secondly allows us to predict stronger ferromagnetic couplings in Cu(II)(2) complexes with larger tetrahedral distortions of the CuN4 coordination environment.

A Novel Dinuclear Nickel(II) Complex with Three Bridges of Cl-, OAc- and (-OCH2CH2O-) Group of N, N, N′, N′-Tetrakis(2-benzimidazolyl methyl-1, 4-di-ethylene amino) Glycol Ether

The novel dinuclear Ni2+ complex [Ni2(μ-Cl)(μ-OAc) (EGTB)]·Cl·ClO4·2CH3OH, where EGTB is N, N, N′, N′-tetrakis (2-benzimidazolyl methyl-1, 4-di-ethylene amino)glycol ether, crystallizes in the orthorhombic space group Pnma with a = 15.272(2), b = 14.768(2), c = 22.486(3) Å, V = 5071.4(12) Å3, Z = 4, Dcalc = 1.414 g cm−3, and is bridged by triply bridging agents of a chloride ion, an acetate and an intra-ligand (-OCH2CH2O-) group. The nickel coordination geometry is that of a slightly distorted octahedron with a NiN3O2Cl arrangement of the ligand donor atoms. The Ni–Cl distance is 2.361(2) Å, and two Ni–O distances are 1.996(5) and 2.279(6) Å. The three Ni–N distances are 2.033(7), 2.060(6), and 2.166(6) Å with the Ni–N bond trans to an ether oxygen the shortest, the Ni–N bond trans to an acetate oxygen the middle and the Ni–N bond trans to Cl the longest.

Phosphate diester hydrolysis in biological relevant compounds by dinuclear metal complexes

The dinuclear Ni2+ and Zn2+ complexes of 1,1′-[(1H-pyrazole-3,5-diyl)bismethylene]-bis(octahydro-1H-1,4,7-triazonine) induce phosphate diester hydrolysis in biological relevant substrates such as thymidine 5′-monophosphate 4-nitrophenylester (TMPNP), guanosine (2′-3′) cyclic phosphate ((2′-3′)cGMP), guanylyl (2′-5′) guanosine ((2′-5′)GpG), adenylyl (3′-5′) adenosine ((3′-5′)ApA), and (2′-deoxy)adenylyl (3′-5′) (2′-deoxy)adenosine ((3′-5′)dApdA). Quantitative measurements of the hydrolysis of TMPNP indicate a Michaelis–Menten mechanism in which the substrate is bound by the dinuclear complex and is hydrolyzed by an intramolecular attack of a coordinated OH− group. Qualitative HPLC measurements of the hydrolysis of the dinucleotide show that in the case of (2′-5′)GpG a cyclic phosphate is formed which then hydrolyses to 2′-GMP and 3′-GMP. The hydrolysis of (2′-3′)cGMP also gave, induced by the dinuclear Zn2+ complex, 2′-GMP and 3′-GMP.

Phosphate and phosphonate ester hydrolysis promoted by dinuclear metal complexes

The kinetics and mechanism of the hydrolysis of bis(4-nitrophenyl)phosphate and (4-nitrophenyl)phenylphosphonate were studied in the presence of the dinuclear Ni2+, Cu2+, and Zn2+ complexes of 1,1-[(1H-pyrazole-3,5-diyl)bis(methylene)]bis(octahydro-1H-1,4,7-triazonine) (LH). Whereas the dinuclear Cu2+ complex does not promote the hydrolysis of these substrates, the dinuclear complexes of Zn2+ and Ni2+ are good catalysts for it. It has been shown by kinetical and 31P NMR studies that the monohydroxo complex [M2(LH−2)]2+ binds the substrate to give an intermediate species, in which an intramolecular attack of the coordinated OH− onto the substrate takes place. Phosphate monoester or phenylphosphonate which are the products of the hydrolysis remain coordinated to the dinuclear complex, and, thus inhibit the further reaction. From the Michaelis–Menten type reactivity which we have observed at high substrate concentrations, KM and kcat values were obtained. The values of KM are very similar to each other as well as for the two substrates as for the two metal ions. In contrast, kcat values are distinctly different, the phosphonate ester being more reactive than the phosphate diester by a factor of 3–4. The major effect is however, due to the metal ion, the dinuclear Ni2+ complex being 50–60 times more reactive than the Zn2+ complex.

Metal Complexes with Macrocyclic Ligands. Part XLVI. Synthesis and structures of dinuclear metal complexes of bis‐macrocycles having a pyrazole bridging unit

AbstractThree bis‐macrocyclic ligands consisting of two N3‐, N2S‐, or NS2‐cyclononane rings, i.e., of two octahydro‐1H‐1,4,7‐triazonine, octahydro‐1,4,7‐thiadiazonine, or hexahydro‐5H‐1,4‐7‐dithiazonine rings, connected by a 1H‐pyrazolediyl unit were prepared. They form dinuclear CuII and NiII complexes which are able to bind one additional exogenous bridging molecule such as Cl−, Br−, N, SO, and 1H‐pyrazol‐1‐ide. The structures determined by X‐ray diffraction show that each Cu2+ is coordinated by the three donor atoms of the macrocyclic ring, by a pyrazolidodiyl N‐atom, by an atom of the exogenous bridging ligand, and sometimes by a solvent molecule. In the majority of the Cu2+ cases, the metal ion exhibits square‐pyramidal or trigonal‐bipyramidal coordination geometry, except in the sulfato‐bridged complex, in which one Cu2+ is hexacoordinated with the participation of a water molecule. The X‐ray structure of the azide‐bridged dinuclear Ni2+ complex was also solved and shows that both Ni2+ centres have octahedral coordination geometries. In all complexes, the 1H‐pyrazolediyl group connecting the macrocycles is deprotonated and bridges the two metal centres, which, depending on the exogenous ligand, have distances between 3.6 and 4.5 Å. In the dinuclear Cu2+ complexes, antiferromagnetic coupling is present. The azido‐bridged complex shows a very strong interaction with −2J ≥ 1040 cm−1; in contrast, the H‐pyrazol‐1‐ide and chloride bridged species have −2J values of 300 and 272cm−1, respectively. Cyclic voltammetry of the Cu2+ complexes in MeCN reveals a strong dependence of the potentials CuII/Cu‐II → CuII/CuI → CuI/CuI on the nature of the donor atoms of the macrocycle as well as on the type of bridging molecule. The more S‐donors are present in the macrocycle, the higher is the potential, indicating a stabilization of the Cu1 oxidation state.

Dinuclear nickel complexes of phenolbased dinucleating macrocycles: Synthesis, structure, and properties

Abstract Dinuclear Ni2(II,II) complexes with the formula [Ni2(Rm,n)](ClO4)2 ((m,n)= (2,2) (1), (2,3) (2), (2,4) (3)) have been obtained where (Rm,n)2- denotes the macrocycles containing two 2,6-bis(iminomethyl)-4-methylphenolate entities combined through two lateral chains, -(CH2)m- and -(CH2)n-, at the imino nitrogens. [Ni2(R2,2)](ClO4)2 (1) crystallizes in the triclinic crystal system, space group P 1, with Z=1, a=8.396(2) A, b= 10.021(2) A, c=8.104(2) A, α=109.56(2)°, β=99.40(2)°, γ=79.89(2)°, V=628.5(3) A3 and Z=1. The refinement converges with R=0.0384 and Rw=0.0415 for 2075 reflections with | Fo | > 3[sgrave](| Fo |). In the centrosymmetric [Ni2(R2,2)]2+, a pair of Ni(II) ions are bridged by two phenolic oxygens with the Ni···Ni separation of 2.801(1) A. Each Ni assumes a planar configuration with Ni-O bond distances of 1.842(3) and 1.838(3) A and Ni-N bond distances of 1.814(3) and 1.823(3) A. In the solid state, 1 is diamagnetic (S1=S2=0) whereas [Ni2(R2,3)]-(ClO4)2 (2) and [Ni2(R2,4)](ClO4)2 (3) ...

Synthesis and co-ordination chemistry of a novel dinucleating chelating triazole ligand. The crystal structure of bis-µ-[4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole-N′, µ-N1,µ-N2,N″,]-bis[aquachloro-nickel(II)] dichloride tetrahydrate

Reaction of 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (abpt) with nickel(II) and cobalt (II) salts produces dinuclear co-ordination compounds. One of the compounds, [Ni2(abpt)2Cl2(H2O)2]Cl2·4H2O, crystallizes in the triclinic space group P with a= 6.840(2), b= 10.199(4), c= 12.480(3)A, α= 78.62(3), β= 76.47(2), γ= 84.17(3)°, and Z= 1. Refinement based on 4 015 independent reflections yielded a value for R′ of 0.034. The dinuclear Ni2(abpt)2 unit is almost planar. The nickel ions are co-ordinated by four nitrogen atoms with N–Ni–N angles of 93.00(4), 76.74(4), 113.67(4), and 76.47(4)° and Ni–N distances of 2.013(1), 2.029(1), 2.155(1), and 2.164(1)A. The axial ligands are a water molecule and a chloride ion. The co-ordination of the metal centres is rhombically distorted octahedral. The uncommon ligand-field spectrum is interpreted along with these findings. Variable-temperature magnetic susceptibility measurements for analogous compounds of NiII and CoII with BF4–, Cl–, or Br– anions revealed that a relatively weak antiferromagnetic exchange is present in these compounds.