A Novel Bimetallic Tetrahedron Cobalt Complex Promoting the Addition of Diethylzinc to Benzaldehyde

Our recent work found a novel bimetallic tetrahedron cobalt complex which can catalyze the addition of diethylzinc to benzaldehyde effectively.

Hydrothermal Reaction, Structure and Magnetic Properties of a Binuclear Cobalt Complex with N-donor Ligand:2-Methyldipyrido[3,2-f:2ˊ3ˊ-h]quinoxaline

One complex [Co1.5（C6H5CHCHCOO）3（Medpq）]·H2O（C6H5CHCHCOO = cinnamic acid, Medpq = 2-methyldipyrido[3,2-f：2,3-h]quinoxaline） 1 has been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectrum, TG, single-crystal X-ray diffraction and magnetic susceptibility measurements. Complex 1 crystallizes in the triclinic system, space group P1, with a = 10.224（5）, b = 14.572（5）, c = 15.139（5）A, α = 112.704（5）, β = 97.168（5）, γ = 109.749（5）, V = 1871.8（13） 3 and Z = 2（at 293（2） K）. In the crystal structure, the Co（1） ion is hexa-coordinated with six atoms from three different cinnamic acid ligands and the symmetric three different cinnamic acid ligands; the Co（2） center adopts a coordination environment with two nitrogen atoms from Medpq ligand and four oxygen atoms from two different cinnamic ligands, assuming a slightly distorted octahedral geometry, respectively. The negative value of the Weiss constant indicates antiferromagnetic exchange interactions between the Co ions.

Hexanuclear ring cobalt complex for photochemical CO_(2) to CO conversion

Photosynthesis in nature has been deemed as the most significant biochemical reaction,which maintains a relatively stable content of O_(2) and CO_(2) in the atmosphere.Herein,for a deeper comprehension of natural photosynthesis,an artificial photosynthesis model reaction of photochemical CO_(2) to CO conversion(CO_(2)+2 H^(+)+2e^(-)→CO+H_(2)O)catalyzed by a homogeneous hexanuclear ring cobalt complex{K_(2)[CoO_(3)PCH_(2)N(CH_(2)CO_(2))_(2)]}_(6)(Co6 complex)is developed.Using the[Ru(bpy)_(3)]^(2+)as a photosensitizer and TEOA as a sacrificial electron donor,an optimal turnover frequency of 503.3 h^(‒1) and an apparent quantum efficiency of 0.81%are obtained.The good photocatalytic CO_(2) reduction performance is attributed to the efficient electron transfer between Co6 complex and[Ru(bpy)_(3)]^(2+),which boosts the photogenerated carriers separation of the photosensitizer.It is confirmed by the j‐V curves,light‐assisted UV‐vis curves,steady‐state photoluminescence spectra and real‐time laser flash photolysis experiments.In addition,the proposed catalytic mechanism for CO_(2) reduction reaction catalyzed by the Co6 complex is explored by the potassium thiocyanate poison experiment,Pourbaix diagram and density functional theory calculations.

A Novel Synthesis of Dimethyl Malonate by Carbonylation of Methyl Chloroacetate Catalyzed by Cobalt Complex

A novel method of preparing dimethyl malonate by carbonylation of methyl chloroacetate catalyzed by Na[Co(CO)(4)] was proposed. Na[Co(CO)(4)] was synthesized in situ in the presence of Na2S2O3 and iron powder. The effects of some reaction parameters such as temperature. CO pressure and the concentrations of catalyst on the yields of dimethyl malonate were discussed. The kinetic data were studied and a possible reaction mechanism was proposed.

Studies on the Displacement Reaction of Trialkylaluminum with Ethylene Catalyzed by Nitrogen Chelate Cobalt Complexes

The catalytic properties of a series of cobalt complexes containing bidenated nitrogen ligand for displacement reaction of trialkylaluminum with ethylene is reported. Effect of different reaction time, temperature and cobalt complexes containing different ligand on catalyst performance has been investigated.

PROSPECTS AND CRUCIAL PROBLEMS IN OLIGOMERIZATION AND POLYMERIZATION WITH IRON AND COBALT COMPLEX CATALYSTS

The discovery of highly active 2,6-bis（imino）pyridyl iron and cobalt complexes provided a milestone of latetransition metal catalysts for ethylene oligomerization and polymerization with being currently investigated for the scale-up process. The crucial problems are remaining in the catalytic systems： the catalytic systems targeting ethylene polymerization produce more oligomers at elevated reaction temperatures, however, there is a recognizable amount of high-molecularweight polyethylene remained in the modified catalytic system for the oligomerization process. Beyond the modification of bis（imino）pyridyl metal complexes, several alternative proeatalysts＇ models have been developed in our group. This review highlighted the achievements in exploring new iron and cobalt complexes with tridentate NNN ligands as procatalysts for ethylene oligomerization and polymerization.

Electrocatalytic hydrogen evolution from water at low overpotentials with cobalt complexes supported by redox-active bipyridyl-NHC donors

Three cobalt complexes bearing tunable,redox-active bipyridyl N-heterocyclic carbene(NHC)-based ligands have been studied for electrocatalytic hydrogen evolution from aqueous solutions.The effect of structural modifications to the ligand framework is investigated across the catalyst series,which includes a non-macrocyclic derivative(1-Co)and 16-(2-Co)and 15-(3-Co)membered macrocycles.A structure-activity relationship is demonstrated,in which the macrocyclic complexes have greater activity compared to their non-macrocyclic counterpart with the most rigid catalyst,supported by the 15-membered macrocycle,performing best overall.Indeed,3-Co catalyzes H2 evolution from aqueous pH 4 acetate buffer with a Faradaic efficiency of 97%at a low overpotential of 330 mV.Mechanistic studies are consistent with formation of a cobalt-hydride species that is subsequently protonated to evolve H2 via a heterolytic pathway.

SYNTHESIS, MAGNETIC PROPERTY AND X-RAY CRYSTAL STUCTURE OF MIXED VALENT COBALT COMPLEX SALT [Co~Ⅲ Cl_2(py)_4][Co~Ⅱ Cl_3(py)]

Complex salt Co_2Cl_5(py)_5 (py=pyridine) was obtained by the reaction of CoCl_2·6H_2O with Bu_4NMnO_4 in pyridine in the presence of benzoic acid. It is monoclinic and crystallizes in space group P2_1/n, fw=690.64, a=28.652(5), b=14.108(4), c=7.424(3) ;β=90.09(1); V=3001(2)~3; Z=4, Dc=1.53g/cm^3. Final R factor is 0.041. The structure consists of a discrete cation [Co~ⅢCl_2(py)_4]^+ and an anion [Co~Ⅱ Cl_3(py)]^-. The Co~Ⅲ ion is coordinated by two Cl^- and four pyridine nitrogen atoms to form an octahedral geometry, and Co~Ⅱ is coordinated by three Cl^- and one pyridine nitrogen atom to form the apices of a tetrahedron. The variable-temperature magnetic susceptility measurement shows no magnet-exchange interaction between Co~Ⅲ and Co~Ⅱ ions.

CRYSTAL STRUCTURE OF A TRINUCLEAR COBALT COMPLEX Co_3(bdt)_3(PBu_3~n)_3 · ~2CH_2C1 (bdt = S_2C_6H_4~2- ) WITH MIXED o-BEN-ZENEDITHIOLATE AND TRIBUTYLPHOSPHINE LIGANDS

Co3(S2C6H4)3{P(C4H9)3}3 ·2CH2Cl2, Mr = 1373. 45, mono-clinic, space group P21/c, a = 16. 110(5), b=36.313(10), c=13. 502(5) A , β= 105. 69(4)% V=7604. 4 A3, Z = 4, Dc = 1. 20 g. cm-3, μ=10. 03 cm-1, and F (000) = 2990. R(Rw) is 0. 086(0. 091) for 4559 observed unique reflections. The three cobalt atoms in the complex form an isosceles triangle with an average Co -Co bond distance of 2. 504(5) A. The average values of Co - S and Co - P bond distances are 2. 271(7) A , and 2. 198(8) A , respectively.

Hydrothermal Synthesis,Crystal Structure and Magnetic Properties of a Novel Cobalt Complex Based on Biphenyl-3,3',4,4'-tetracarboxylate

A novel cobalt complex,[Co2（bptc）（bix）1.5]（1,H4bptc=3,3＇,4,4＇-biphenyltetra-carboxylic acid,bix = 1,4-bis（imidazol-1-ylmethyl）benzene）,has been hydrothermally prepared and characterized by IR spectroscopy,elemental analysis and single-crystal X-ray diffraction.The crystal is of triclinic system,space group P1 with a=10.770（7）,b=12.245（8）,c=13.514（9）,α=102.829（8）,β=107.734（8）,γ=98.833（9）°,C37H27N6O8Co2,Mr=801.51,V=1607.5（18）3,Dc=1.656g/cm3,F（000）=818,μ=1.100mm-1,Z=2,the final R = 0.0694 and wR = 0.1543 for 3034 observed reflections（I2σ（I））.In the title complex,the two Co（Ⅱ） ions are in different coordination environments with distorted octahedral and trigonal bipyramidal geometries,respectively.The Co atoms are linked together through hexadentate bptc ligands,giving rise to 2D layers which are bridged by the bix ligands into a 3-D supramolecular network.Magnetic susceptibilities of 1 reveal weak antiferromagnetic exchange interactions between the adjacent Co（Ⅱ） ions.

Synthesis and Characterization of a Cobalt Complex with Maleate and Pyridine

A new polymeric cobalt complex [Co(-male)(py)(H2O)]n (male = maleate; py = pyridine) 1 was prepared by cobalt chloride hexahydrate with disodium maleate and pyridine in an alcohol-aqueous solution. Single-crystal X-ray analysis has revealed that 1 crystallizes in the orthor- hombic system, space group Pnma with a = 18.001(1), b = 7.6001(6), c = 7.4731(6) ? V = 1022.4(1) 3, Z = 4, C9H9CoNO5, Mr = 270.10, Dc = 1.755 g/cm3, F(000) = 548, m(MoK? = 1.683 mm-1, S = 1.002, the final R = 0.0280 and wR = 0.0746 for 883 observed reflections with I > 2s(I). The structure analysis shows an approximate octahedral coordination environment of metal center. The Co(II) ions are bridged by maleic anions in a rare tetradentate coordination fashion with a syn-anti coplanar con- formation of the carboxyl group, forming a two-dimensional corrugated 2-D structure which is further attached into a three-dimensional framework via non-classical CH…O interactions between adjacent layers.

Probing Photocatalytic Hydrogen Evolution of Cobalt Complexes: Experimental and Theoretical Methods

This work reports on the synthesis and characterization of a series of Schiff-base cobalt(III)complexes 1〜4 that exhibit an obvious catalytic activity for hydrogen production in aqueous solution using fluorescein(FL)and triethanolamine(TEOA)as photosensitizer and electron donor,respectively.The complexes display the capability of splitting of water for H2 evolution.Under optimized conditions,complex 3 shows better properties for photocatalysis,25 mg of which can release 152.3μmol of H_(2) after irradiation for 3 h.The mechanism for light-driven H_(2) production was explored by experiments and density functional theory(DFT).Meanwhile,the reason of releasing hydrogen was explained theoretically in detail.The research results will help to understand the interaction of cobalt complexes with the photosensitizer and design new photocatalysis for the future.

Synthesis and Catalytic Activity of Nickel(Ⅱ)and Cobalt(Ⅱ) Complexes Involving Chiral Leucinol

The title nickel complex I and cobalt complex II were obtained separately from the direct reaction of D-（＋）-leucinol with Ni（II） chloride and L-（-）-leucinol with Co（II） acetate tetra- hydrate in anhydrous methanol. The crystal structures of I and II were determined by single-crystal X-ray diffraction and further characterized by elemental analysis and IR. For I： [Ni（C18H45N3O3）]Cl2, orthorhombic, P212121, a = 11.2807（9）, b = 14.7115（11）, c = 16.3580（13） A, V = 2714.7（4） A3, Z = 4, Pcalcd = 1.177 Mg/m3, the final R = 0.0407, and 16539 reflections observed with I 〉 2σ（/）; For II： [Co（C45HI08N6015）], trigonal, R3：H, a = 23.981（3）, b =23.981（3）, c = 10.8925（15） A, γ = 120°, V = 5425.1（14） A3, Z = 3, Pcalcd = 1.002 Mg/m3, the final R = 0.0625 for 16556 observed reflections with I 〉 2σ（I）. The complexes were then used to catalyze the Henry reaction and obtained good catalytic results. The catalytic activity of the complexes was determined by IH NMR. And research is going towards the application to other organic reactions such as cyanosilylation reaction.

Secondary Synthesis of Two Cobalt Complexes by the Use of 5-Sulfosalicylate and 1 ,lO-Phenanthroline and Their Crystal Structures

Cobait（Ⅱ） nitrate reacted with 1,10-phenanthroline （phen） and 5-sulfosaiicylic acid （H3ssal） to yield the cobait（Ⅰ） complex [Co（phen）2（H2O）2]（Hssal）o4H2O （1） and the reaction of 1 with copper acetate led to a novel complex [Co（phen）（H2O）4][Cu2（ssal）2（phen）2]·5H2O （2）. These two complexes were cationanion species and the cationic motif [Co（phen）2（H2O）2]^2＋of 1 could be converted to [Co（phen）（H2O）4]^2＋ in the formation process of new anion [Cu2（phen）2（ssal）2]^2- of 2. In both complexes abundant hydrogen bonds construct different supramolecular architectures, thus the conversion reaction can provide a new path to create novel supramolecular network.

Molecular and Supramolecular Structures of Manganese(Ⅱ) and Cobalt(Ⅱ) Complexes with 1-Carboxymethylpyridinium-4-carboxylate

Two complexes with a zwitterionic dicarboxylate ligand,Mn（L）2（H2O）4 1 and Co（L）2（H2O）4 2（L = 1-carboxymethylpyridinium-4-carboxylate）,were synthesized and structurally characterized.Complex 1 crystallizes in monoclinic,space group P21 with a = 6.490（2）,b = 19.210（7）,c = 7.813（3） ,β = 92.716（5）o,V = 972.9（6） 3,Z = 2,Mr = 487.28,Dc = 1.663 g/cm3,F（000） = 502,μ = 0.749 mm-1,S = 1.060,the final R = 0.0377 and wR = 0.0893 for 3292 observed reflections with I 2σ（I）.Complex 2 is isomorphous with 1,with a = 6.478（2）,b = 19.052（7）,c = 7.742（3） ,β = 92.690（4）o,V = 954.6（6） 3,Z = 2,Mr = 491.28,Dc = 1.709 g/cm3,F（000） = 506,μ = 0.971 mm-1,S = 1.035,the final R = 0.0425 and wR = 0.0809 for 3289 observed reflections with I 2σ（I）.In the compounds,the mononuclear [M（L）2（H2O）4] units with trans-octahedral coordination geometry are linked into 3D architectures via hydrogen bonding（or second-sphere coordination） involving carboxylate groups and coordinated water molecules.The 3D networks illustrate a 3,8-connected net with Schlfli symbol（4·62）2（42·623·83）.

Synthesis and One-dimensional Structure of Cobalt(Ⅱ) Complex [(NaOC_2H_5)CoL_2]_n

The treatment of bis(2-hydroxybenzyl)-amine(HL) with NaOH and Co(Ⅱ)(NO) 2 gives isostructural one-dimensional coordination polymers [(NaOC2H5)CoL2]n(1). The cobalt ions have an octahedral geometry and are coordinated by two crystallographically independent ligands which are further linked by μ -O\-\{phenol\} bridged Co and Na atoms to give a one-dimentional structure.

SYNTHESIS, CHARACTERIZATION AND CATALYTIC ACTIVITY OF N,N'-BIS(3-ALLYL SALICYLIDENE)ETHYLENEDIAMINE COBALT(Ⅱ) SCHIFF BASE COMPLEX ANCHORED ON A NEW POLYMER SUPPORT

A new chelating polymer support has been prepared by suspension copolymerization of synthesized N,N'-bis(3- allyl salicylidene)ethylenediamine monomer Schiff base (N,N'-BSEDA) with styrene (St) and divinylbenzene (DVB) using azobisisobutyronitrile (AIBN) as initiator in the presence of poly(vinyl alcohol). The content and complexation ability of monomer Schiff base (N,N'-BSEDA) for cobalt ions in prepared crosslinked polymer beads have shown dependence on the amount of DVB used in reaction mixture. The amount of monomer Schiff base (N,N '-BSEDA) in crosslinked beads showed a substantial decreasing trend at high concentration of DVB in the reaction mixture (> 1.5 mol dm-3), hence the efficiency of complexation (EC%) and cobalt ion loading (EL%) of polymer beads showed a decreasing trend. The structure of monomer Schiff base (N,N'-BSEDA) and its cobalt complex on polymer support was elucidated by IR, UV and magnetic measurements. The catalytic activity of polymer bound cobalt Schiff base complex was evaluated by analyzing kinetic data of decomposition of hydrogen peroxide in the presence of either supported cobalt complex or free cobalt complex. The activation energy for the decomposition of hydrogen peroxide by polymer supported cobalt complex was found to be low (33.37 kJ mol-1) in comparison with unsupported cobalt complex (56.35 kJ mol-1). On the basis of experimental observations, reaction steps are proposed and a suitable rate expression derived.

Synthesis of a New Cobalt(Ⅱ)Complex and its Interaction with DNA

A new complex of bis(N-benzyl benzotriazole-N3) dichloro Co(II) (Co(II)L2Cl2) was synthesized and its crystal was characterized. The interaction of this new complex with fs-DNA was studied by electrochemical and UV spectrophotometric method. In 0.01 mol/L pH 4.2 Tris-HCl buffer solution Co(II)L2Cl2 has two reductive peaks with peak potentials at 0.38 V and 0.27 V, respectively, and an oxidative peak at 1.05 V. After the addition of DNA, the peak currents decrease and the peak potential at 0.27 V shifts negatively. The UV spectrophotometric experiment indicates that the maximum absorbance of Co(II)L2Cl2 at 204 nm decreases and exhibits bathochromic shift after the addition of DNA. All the results reveal that Co(II)L2Cl2 binds with DNA by intercalation as well as electrostatic interaction.

Synthesis of Unsymmetrical Bissalicylaldimine Ligands and bis-Schiff Base Cobalt Complexes with Benzo-10-aza-15-crown-5 Pendant

Novel unsymmetrical bissalicylaldimine bis-Schiff bases with a benzo-10-aza-15-crown-5 pendant and their cobalt complexes have been synthesized via condensation of 3 or 5-[（benzo-10-aza-15-crown-5）-10-ylmethyl] salicylaldehyde with the half unit Schiff bases and characterized by ^1H NMR, IR, mass spectroscopy, elemental analysis, molar conductances and molar magnetic susceptibility.

Studies on Transition Metal Complexes of Schiff Base( Ⅰ )——Oxygen-carrying Properties of Cobalt( Ⅱ )Schiff Base Complexes

Introduction The compounds that can take up and release molecular oxygen reversibly is of significance because they can be used as model compounds for the study of the reversible oxygenation mechanisms involved in the very complex natural oxygen carriers, e.g., the hemoglobins and hemocyanins, and as the means of separating molecular oxygen from the air. The dioxygen carriers extensively studied are the Cobalt