Ni Center Research Articles

Electron-State Confinement of Polysulfides for Highly Stable Sodium-Sulfur Batteries.

Confinement of polysulfides in sulfur cathodes is pivotal for eliminating the "shuttle effect" in metal-sulfur batteries, which represent promising solutions for large-scale and sustainable energy storage. However, mechanistic exploration and in-depth understanding for the confinement of polysulfides remain limited. Consequently, it is a critical challenge to achieve highly stable metal-sulfur batteries. Here, based on a 2D metal-organic framework (2D MOF), a new mechanism to realize effective confinement of polysulfides is proposed. A combination of in situ synchrotron X-ray diffraction, electrochemical measurements, and theoretical computations reveal that the dynamic electron states of the Ni centers in the 2D MOF enable the interaction between polysulfides and the MOF in the discharge/charge process to be tuned, resulting in both strong adsorption and fast conversion kinetics of polysulfides. The resultant room-temperature sodium-sulfur batteries are amongst the most stable reported so far, thus demonstrating that the new mechanism opens a promising avenue for the development of high-performance metal-sulfur batteries.

Ferromagnetic coupling in two tetranuclear Ni(II) complexes with cubane–like Ni4(μ3–O)4 core: Structure, spectroscopic and luminescence properties

Two new tetranuclear [Ni4(L1)4(MeOH)4] (1) and [Ni4(L2)4(EtOH)(MeOH)(H2O)2]·H2O (2) complexes have been synthesized by solvothermal method. We here report the spectroscopic, structural, photoluminescence and magnetic properties of both complexes. Complex 1 and 2 exhibit a cubane-like Ni4O4 structure. All Ni(II) center has a slightly distorted octahedral geometry. The optical properties of 1 and 2 have been analyzed by photoluminescence spectra obtained in the visible region. Variable-temperature (2–300 K) magnetic studies have been analyzed by using the Heisenberg Hamiltonian model with 2J exchange pathways. The best–fit parameters in analysis of the magnetic data are found as J1 = −2.38 cm−1, J2 = +5.43 cm−1, g = 2.2, Nα = 0.08 for 1, J1 = −2.34 cm−1, J2 = +4.90 cm−1, g = 2.2 and Nα = 0.11 for 2. These results are shown dominant ferromagnetic interactions between Ni(II) centers. Finally, the strong luminescence emission of both complexes makes them potentially useful photoactive material in developing optical and electronic materials.

A dinuclear nickel catalyst based on metal–metal cooperation for electrochemical hydrogen production

In the quest for efficient metal catalysts for hydrogen production, a new dinuclear nickel complex of formula [{(μ-2-thiazolethiolate)Ni(1,3-bis(diphenylphosphino)propane)}2](BF4)2 (2) has been synthesized. Complex 2 shows electrochemical catalytic behavior for hydrogen production with a overpotential of 0.26 V, a current efficiency of 59%, and a turnover number of 6.4. The lack of catalytic behavior of a related mononuclear complex under the same conditions suggests that the cooperation between the two Ni centers plays a pivotal role in the catalytic behavior.

Tweaking Nickel with Minimal Silver in a Heterogeneous Alloy of Decahedral Geometry to Deliver Platinum‐like Hydrogen Evolution Activity

Five-fold intertwined Agx Ni1-x (x=0.01-0.25) heterogeneous alloy nanocrystal (NC) catalysts, prepared through unique reagent combinations, are presented. With only ca. 5 at % Ag (AgNi-5), Pt-like activity has been achieved at pH 14. To reach a current density of 10 mA cm-2 the extremely stable AgNi-5 requires an overpotential of 24.0±1.2 mV as compared to 20.1±0.8 mV for 20 % Pt/C, both with equal catalyst loading of 1.32 mg cm-2 . The turnover frequency (TOF) is as high as 2.1 H2 s-1 at 50 mV (vs. RHE). Site-specific elemental analyses show the Ag:Ni compositional variation, where the apex and edges of the decahedra are Ag-rich, thereby exposing Ni onto the faces to achieve maximum charge transport for an exceptional pH universal HER activity. DFT calculations elucidate the relative H-atom adsorption capability of the Ni centers as a function of their proximity to Ag atom.

Tweaking Nickel with Minimal Silver in a Heterogeneous Alloy of Decahedral Geometry to Deliver Platinum‐like Hydrogen Evolution Activity

AbstractFive‐fold intertwined AgxNi1−x (x=0.01–0.25) heterogeneous alloy nanocrystal (NC) catalysts, prepared through unique reagent combinations, are presented. With only ca. 5 at % Ag (AgNi‐5), Pt‐like activity has been achieved at pH 14. To reach a current density of 10 mA cm−2 the extremely stable AgNi‐5 requires an overpotential of 24.0±1.2 mV as compared to 20.1±0.8 mV for 20 % Pt/C, both with equal catalyst loading of 1.32 mg cm−2. The turnover frequency (TOF) is as high as 2.1 H2 s−1 at 50 mV (vs. RHE). Site‐specific elemental analyses show the Ag:Ni compositional variation, where the apex and edges of the decahedra are Ag‐rich, thereby exposing Ni onto the faces to achieve maximum charge transport for an exceptional pH universal HER activity. DFT calculations elucidate the relative H‐atom adsorption capability of the Ni centers as a function of their proximity to Ag atom.

Influence of Ring Contraction on the Electronic Structure of Nickel Tetrapyrrole Complexes: Corrole vs Porphyrin

The influence of the contracted corrole macrocycle, in comparison to the larger porphyrin macrocycle, on the electronic structure of nickel was studied with X-ray and ultraviolet photoelectron spectroscopy (XPS, UPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Synthesis and in situ characterization of the Ni complexes of octaethylporphyrin (NiOEP) and hexaethyldimethylcorrole (NiHEDMC) were performed in ultra-high vacuum. XPS and NEXAFS spectra reveal a +2 oxidation state and a low-spin d8 electron configuration of Ni in both complexes, despite the formal trianionic nature of the corrole ligand. UPS, in combination with density functional theory (DFT) calculations, support the electronic structure of a Ni(II) corrole with a π-radical character of the ligand. The NEXAFS spectra also reveal differences in the valence electronic structure, which are attributed to the size mismatch between the small Ni(II) center and the larger central cavity of NiOEP. Analysis of the gas-phase structures shows that the Ni−N bonds in NiOEP are 4%–6% longer than those in NiHEDMC, even when NiOEP adopts a ruffled conformation. The individual interactions that constitute the Ni−ligand bond are altogether stronger in the corrole complex, according to bonding analysis within the energy decomposition analysis and the natural orbitals for chemical valence theory (EDA-NOCV).

Binuclear chiral Ni(II) complex of tridentate OON chiral Schiff base ligand, 1-((E)-(((1S,2R)-2-hydroxy-2,3-dihydro-1H-inden-1-yl)imino)methyl)naphthalen-2-ol

Binuclear Ni(II) chelating complex with chiral Schiff base 1-((E)-(((1S,2R)-2-hydroxy-2,3-dihydro-1H-inden-1-yl)imino)methyl)naphthalene-2-ol [Ni2L2] has been synthesized. The structure of [Ni2L2] was elucidated with single-crystal X-ray diffraction, spectroscopic (UV–vis, FTIR, mass) analysis and substantiated with computational (DFT) method. The crystal system of binuclear complex is monoclinic with space group P21/c. The asymmetric unit having two tridentate OON-donor sets are in slightly distorted square-planar geometry around each Ni(II) center. The distortion is due to strong coordination between two Ni(II) ions. The stabilization of complex [Ni2L2] occurs due to noncovalent interactions and hydrogen bonding (C–H…C and C–H…O), H…H, O…H, C…H, and C–H…π stacking interactions, and van der Waals interactions. DFT optimization, with little acceptable discrepancies, correlate with the X-ray diffraction data as well as TD DFT optimization for electronic transitions of the complex showing acceptable alignment with spectroscopic data. The complex displays appreciable inclination towards DNA-binding with calf-thymus DNA (CT DNA) and the DNA-binding studies were carried out by UV–visible spectroscopy, fluorescence spectroscopy, cyclic voltammetry, viscosity measurements, and CD spectroscopy. The DNA-binding study reveals that the order of binding constant value is in 105 M − 1, supporting the effective efficiency of binding and the modes of binding are intercalation and groove.

Self-assembly of a nonanuclear NiII cluster via atmospheric CO2 fixation: synthesis, structure, collision-induced dissociation mass spectrometry and magnetic property.

A novel nonanuclear nickel(ii) cluster identified as [Ni9(OH)6(CO3)2(ba)8(Hdmpz)6(DMF)2]·EtOH·2DMF (SD/Ni9a, Hba = benzoic acid, Hdmpz = 3,5-dimethyl-1H-pyrazole) is successfully constructed from mixed ligands. The single-crystal X-ray diffraction (SCXRD) structural analysis confirms the composition and reveals the "drum-like" inner core structure surrounded by ba- and DMF. Six Hdmpz ligands in their neutral form further sandwich the "drum" up and down, and is hydrogen bonded with two carbonate anions that are derived from the atmospheric CO2 with the help of Et3N. Electrospray ionization mass spectrometry (ESI-MS) reveals that the SD/Ni9a maintains an intact core in the solution with a slight exchange of outer ligands. Detailed collision-induced dissociation (CID) experiments reveal the collision energy (CE)-promoted ligand loss and exchange between ba- and Hdmpz. Furthermore, the magnetic study shows that there is no interaction between the Ni centers at room temperature, whereas the ferromagnetic coupling between the Ni centers is found with an S = 3 spin ground state of the cluster at low temperature. Moreover, the UV-vis spectrum and the photocurrent response measurements show its good optical properties with an indirect bandgap of about 2.35 eV and fast current response upon visible light irradiation.

Ligand architecture for triangular metal complexes: a high oxidation state Ni3 cluster with proximal metal arrangement.

A new multidentate tetraanionic ligand platform for supporting trinuclear transition metal clusters has been developed. Two trisphenoxide phosphinimide ligands bind three Ni centers in a triangular arrangement. The phosphinimide donors bridge in μ3 fashion and the phenoxides complete a pseudo-square planar coordination sphere around each metal center. Electrochemical studies reveal two pseudo-reversible oxidation events at notably low potentials (-0.80 V and +0.05 V). The one electron oxidized species was characterized structurally, and it is assigned as a NiIII-containing cluster.

Synthesis, X-ray structure and DFT calculation of magnetic properties of binuclear Ni(II) complex with tridentate hydrazone-based ligand

Abstract: Binuclear double end-on azido bridged Ni(II) complex (1) with composition [Ni2L2(?-1,1-N3)2(N3)2]?6H2O, (L = (E)-N,N,N-trimethyl-2-oxo-2-(2- -(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethan-1-amin) was synthesized and characterized by single-crystal X-ray diffraction method. Ni(II) ions are hexacoordinated with the tridentate heteroaromatic hydrazone-based ligand and three azido ligands (one terminal and two are end-on bridges). DFT calculations revealed that coupling between two Ni(II) centers is ferromagnetic in agreement with binuclear Ni(II) complexes with similar structures.

Hard X-ray-based techniques for structural investigations of CO2 methanation catalysts prepared by MOF decomposition.

Thermal decomposition of metal-organic framework (MOF) precursors is a recent method to create well-dispersed metal centers within active catalyst materials with enhanced stability, as required for dynamic operation conditions in light of challenges caused by the renewable energy supply. Here, we use a hard X-ray-based toolbox of pair distribution function (PDF) and X-ray absorption spectroscopy (XAS) analysis combined with X-ray diffraction and catalytic activity tests to investigate structure-activity correlations of methanation catalysts obtained by thermal decomposition of a Ni(BDC)(PNO) MOF precursor. Increasing the decomposition temperature from 350 to 500 °C resulted in Nifcc nanoparticles with increasing particle sizes, alongside a decrease in Ni2+ species and strain-induced peak broadening. For lower temperatures and inert atmosphere, Ni3C and NiO phases co-existed. A graphitic shell stabilized the Ni particles. Compared to an inert atmosphere, reducing conditions led to larger particles and a faster decomposition of the MOF precursor. Catalytic studies revealed that the decomposition at an intermediate temperature of 375 °C in 5% H2/He is the best set of parameters to obtain high specific surface areas while maintaining particle sizes that feature many active Ni centers for the formation of CH4.

Attaining highly branched polyethylene elastomers by employing modified α-diiminonickel(II) catalysts: Probing the effects of enhancing fluorine atom on the ligand framework towards mechanical properties of polyethylene

A novel panel of 1-(2,6-dibenzhydryl-3,4-difluorophenylimino)-2-aryliminoacenaphthylenes was synthesized and reacted with (DME)NiBr2 to give rise to mono and di-nuclear complexes with the general formula of LNiBr2 and L2Ni2Br4, respectively. All the ligands were characterized by elemental analysis, FT-IR, 1H, 13C, 19F NMR spectroscopy, and their complexes were analyzed by elemental analysis and FT-IR spectroscopy. The true coordination nature of the ligands in Ni2 and Ni5 was confirmed through single-crystal XRD studies and thus reveal the distorted square-pyramidal and tetrahedral geometry around the Ni(II) center, respectively. In connection with this, complex Ni2 forms a di-nuclear structure whereas Ni5 formed a mono-nuclear structure in the solid-state. These complexes were tested as catalysts for the polymerization of ethylene in the presence of aluminum reagents like methylaluminoxane (MAO), modified methylaluminoxane (MMAO) or dimethylaluminum chloride (Me2AlCl). The obtained polyethylenes are highly branched and ultra-high molecular weight (Mw = 11.42 × 105 g mol−1, Tm = 82.6 °C) with narrow polydispersity. The mechanical properties of the polyethylenes are analyzed through dynamic mechanical analysis (DMA), monotonic stress-strain test and thus revealed that high tensile strength, good elastomeric recovery (up to 63%) and highest elongation ability (up to 2592.6%) without break are the key highlights of the present work.

Nickel(II/IV) Manifold Enables Room-Temperature C(sp3)-H Functionalization.

This Article demonstrates a mild oxidatively induced C(sp3)-H activation at a high-valent Ni center. In contrast with most C(sp3)-H activation reactions at NiII, the transformation proceeds at room temperature and generates an isolable NiIV σ-alkyl complex. Density functional theory studies show two plausible mechanisms for this C-H activation process involving triflate-assisted C-H cleavage at either a NiIV or a NiIII intermediate. The former pathway is modestly favored over the latter (by ∼3 kcal/mol). The NiIV σ-alkyl product of C-H cleavage reacts with a variety of nucleophiles to form C(sp3)-X bonds (X = halide, oxygen, nitrogen, sulfur, or carbon). These stoichiometric transformations can be coupled using N-fluoro-2,4,6-trimethylpyridinium triflate as a terminal oxidant in conjunction with chloride as a nucleophile to achieve a proof-of-principle NiII/IV-catalyzed C(sp3)-H functionalization reaction.

Efficient Photocatalytic CO2 Reduction by a Ni(II) Complex Having Pyridine Pendants through Capturing a Mg2+ Ion as a Lewis-Acid Cocatalyst.

We have synthesized a new Ni(II) complex having an S2N2-tetradentate ligand with two noncoordinating pyridine pendants as binding sites of Lewis-acidic metal ions in the vicinity of the Ni center, aiming at efficient CO production in photocatalytic CO2 reduction. In the presence of Mg2+ ions, enhancement of selective CO formation was observed in photocatalytic CO2 reduction by the Ni complex with the pyridine pendants through the formation of a Mg2+-bound species, as compared to the previously reported Ni complex without the Lewis-acid capturing sites. A higher quantum yield of CO evolution for the Mg2+-bound Ni complex was determined to be 11.1%. Even at lower CO2 concentration (5%), the Ni complex with the pendants exhibited comparable CO production to that at the CO2-saturated concentration (100%). The Mg2+-bound Ni complex was evidenced by mass spectrometry and 1H NMR measurements. The enhancement of CO2 reduction by the Mg2+-bound species should be derived from cooperativity between the Ni and Mg centers for the stabilization of a Ni-CO2 intermediate by a Lewis-acidic Mg2+ ion captured in the vicinity of the Ni center, as supported by DFT calculations. The detailed mechanism of photocatalytic CO2 reduction by the Ni complex with the pyridine pendants in the presence of Mg2+ ions is discussed based on spectroscopic detection of the intermediate and kinetic analysis.

On the Influence of the Extent of Oxidation on the Kinetics of the Hydrogen Electrode Reactions on Polycrystalline Nickel

The influence of the extent of oxidation of Ni electrodes on the kinetics of the hydrogen oxidation (HOR) and evolution (HER) reactions has been explored by combining an experimental cyclic voltammetry and chronoamperometry study with microkinetic modeling. The HOR/HER specific activity of the Ni/NiOx electrodes follows a volcano-type dependence with a maximum at 30% NiOx coverage corresponding to a 14-fold increase (nominally from 2.2 to 32.8 μA cm−2Ni) of the specific activity calculated as the exchange current density normalized by the electrochemical surface area of Ni active sites. The kinetic model suggests that the experimentally observed changes in the shape of current-potential curves as well as the HOR/HER specific activities are mostly due to the NiOx coverage–dependent strength of adsorption of hydrogen atoms. The latter is accompanied by an increase of the rate of the Volmer step and a decrease of the potential of OHad adsorption on Ni centers in the vicinity of surface Ni oxides.

(Benz-)imidazolin-2-ylidene-benzimidazolatonickel(II) Chelates: Syntheses, Structures, and Tuning of Noninnocent Chelate Ligand Behavior.

The deprotonation of 1-(1H-benzimidazol-2-yl)-3-methylbenzimidazolium hexafluorophosphate (2MeH2[PF6]) and 1-(1H-benzimidazol-2-yl)-3-isopropylbenzimidazolium hexafluorophosphate (2iPrH2[PF6]) with potassium tert-butoxide in THF afforded the benzimidazolium-benzimidazolates 2MeH and 2iPrH. The "instant carbene" behavior of these conjugated mesomeric betaines was demonstrated by trapping their carbenic tautomers 2'MeH and 2'iPrH with elemental sulfur and selenium, which afforded the corresponding thio- and selenourea derivatives 2'MeHE and 2'iPrHE (E = S, Se). The treatment of 2MeH and 2iPrH with nickelocene furnished the nickel(II) complexes [NiCp(2'Me)] and [NiCp(2'iPr)], which contain an anionic C,Namido-chelating NHC ligand. The electronic structure and redox behavior of the nickel(II) chelates were investigated, as well as those of the closely related chelates [NiCp(1'Me)] and [NiCp(1'iPr)] derived from the corresponding imidazolium-benzimidazolates 1MeH and 1iPrH. According to DFT calculations, the highest occupied molecular orbital (HOMO) is located over the NiCp moiety and the π system of the chelate ligand with a large contribution from the (benz-)imidazolate moiety. Cyclic voltammetry revealed a reversible oxidation to the monocation [NiCp(L)]+ (E1/2 = 0.315, 0.222, 0.396, 0.265 V vs ferrocene/ferrocenium for L = 1'Me, 1'iPr, 2'Me, 2'iPr, respectively) in CH2Cl2/0.1 M n-Bu4N[B(ArF)4] (B(ArF)4- = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate), and isosbestic behavior was found in UV-vis-NIR spectroelectrochemical experiments. The different redox potentials reflect the different donor/acceptor properties of the NHC part of the chelate ligands, with 1'iPr being the strongest and 2'Me the weakest net electron donor. The EPR spectroscopic signature of [NiCp(2'Me)]+ in CH2Cl2/0.1 M n-Bu4N[B(ArF)4] at 100 K is consistent with a chelate-ligand-based radical with strong spin-orbit coupling to the Ni center. In contrast, the EPR spectra of [NiCp(1'Me)]+, [NiCp(1'iPr)]+, and [NiCp(2'iPr)]+ indicate that these monocations are best described as NiIII complexes, the comparatively higher contribution of the NiIII(L) vs the NiII(L•+) valence tautomer being supported by the results of open-shell DFT calculations.

Syntheses, crystal structures and magnetic properties of redox active cyanide-bridged trinuclear Ru-M2 (M = Co, Ni, Cu) complexes

Three redox active cyanide-bridged trinuclear complexes trans-(DMAP)4Ru(μ-CN)2- [M(PY5Me2)]2[PF6]4 (M = Co (1), Ni (2), Cu (3)) {DMAP = 4-dimethylamino-pyridine, PY5Me2 = 2,6-bis(1,1-bis(2-pyridyl)ethyl)pyridine} were designed, synthesized and fully characterized by single-crystal X-ray diffraction, elemental analysis, IR spectrum, cyclic voltammetry and magnetic measurement. Due to the Jahn-Teller effect of CuII ion, the structure of compound 3 shows peculiar disordered configuration. Cyclic voltammograms show that compounds 1 and 2 possess redox-active Co and Ni centers except for the Ru center. Magnetic measurements show compound 1 behaves as paramagnetism with strong magnetic anisotropy of CoII ion and compound 2 has a very weak anti-ferromagnetic coupling constant, but compound 3 is only simple paramagnetism.

DFT studies on the structure and stability of tetraaza macrocyclic nickel(II) complexes containing dicarbinolamine ligand moiety

Density functional theory calculations at M052X/6-311++G** level were performed to understand the structure and stability of Ni(II) tetraaza macrocyclic dicarbinolamine complex 1. The preferential stability of 1 over the hitherto unknown Ni(II) complex having fully conjugated macrocyclic ligand 2, is examined by analyzing geometric and electronic structures and energy considerations. The present calculations predict that in the trans (C2) structure, 1 is 102 kcal/mol more stable than its components 2 and 2(OH) at M062X-D3/def2-QZVP//M052X/6-311++G** level. This significant stabilization explains the formation of 1 as experimentally observed. The calculations support a distorted square planar environment for Ni in 1, in agreement with the observed spectral and magnetic properties. In order to understand the stability of 1, we examined the second-order stabilizing interactions in natural bond orbital (NBO) basis, the role of the noncovalent dispersion energy, macrocyclic cavity size, Ni-ligand covalent bond strength, natural electronic population on the atomic centers and the nature of the frontier molecular orbitals in the complexes. The present study reveals that the higher stability of 1 over 2 is primarily due to the stronger covalent bonds between the Ni(II) centre, and two of the coordinating nitrogen atoms in 1 than in 2 and significant second-order stabilizing interactions originating from the NBOs involving the oxygen atoms. Density functional theory calculations at M052X/6-311++G** level explains the structure and stability of Ni(II) tetraaza macrocyclic dicarbinolamine complex.

VIBRATIONAL SPECTROSCOPIC AND THERMAL INVESTIGATIONS OF THE CYANO-BRIDGED POLYMERIC COMPLEXES WITH 3-AMINOMETHYLPYRIDINE


 
 New cyano-bridged
 polymeric complexes formulated as [Co(H2O)(ampy)Ni(CN)4]∙H2O
 and [Ni(ampy)2Ni(CN)4]∙H2O (ampy = 3-aminomethylpyridine: abbreviated henceforth as Co-Ni-ampy and Ni-Ni-ampy) have been
 obtained in powder form and characterized by vibrational (infrared and Raman)
 spectroscopy, thermal and elemental analyses. In previous study, structure of
 complex [Cd(NH3)(ampy)Ni(CN)4]n
 (Cd-Ni-ampy) was determined by single crystal X-ray diffraction methods. In
 this complex, the coordination environment of the Cd(II) ions are distorted
 octahedral geometry, whereas around the Ni(II) center is pyramidal. The
 spectral features suggest that Cd-Ni-ampy with Co-Ni-ampy are similar to each
 other and the ampy ligand is coordinated to metal ions as bidentate ligand. In
 addition, complex Ni-Ni-ampy is similar in structure to the Hofmann type
 complexes and its structure consists of polymeric layers of │Ni–Ni(CN)4│∞
 with the ampy ligand bounded to the nickel(II) atom. Thermal stabilities and
 decomposition products of the complexes were investigated using TG, DTG and DTA
 curves in the temperature range of 30 – 700 °C in the static air atmosphere.

Formation of a carbonato bridged Ni4-complex by atmospheric CO2 fixation: Crystal structure and magnetic properties

Reaction of NiCl2·6H2O with a simple N2O donor tridentate reduced Schiff base ligand, 2-[(3-methylamino-propylamino)-methyl]-4-nitro-phenol (HL) yielded a tetranuclear complex, [Ni4L4Cl2(µ4-CO3)(CH3CN)2]·0.5CH3CN·H2O (1) which was structurally characterized. Complex 1 is an example of atmospheric CO2 fixation model with uniqueness in a new µ4-κ2:κ2:ƞ1:ƞ1-carbonato coordination mode to Ni(II). Involvement of this type of NNO donor ligands for the synthesis of carbonato bridged polynuclear compounds by spontaneous atmospheric CO2 fixation is very rare. All Ni(II) ions are in octahedral environment in 1 with phenoxido and hexadentate µ4-carbonato bridging. Variable temperature magnetic measurements showed overall antiferromagnetic coupling between Ni(II) centers with J1 = −60.32 cm−1, J2 = −19.52 cm−1, J3 = 2.6 cm−1 and J4 = 3.3 cm−1. The magnetic behavior of the complex has been explained considering the carbonato and phenoxido bridging angles.