Novel cobalt(Ⅱ) complexes of amino acids-Schiff bases catalyzed aerobic oxidation of various alcohols to ketones and aldehyde

Two cobalt（Ⅱ） complexes 1 and 2 of Schiff bases derived from amino acids were synthesized and used for oxidation of benzyl alcohol with molecular oxygen at different conditions of pH,solvent,temperature and complex/alcohol molar ratio to optimize reaction conditions and to evaluate the catalytic efficiency of new cobalt Schiff base complexes.Under obtained optimum conditions,various alcohols were oxidized to corresponding aldehydes and ketones.

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.

Hydrothermal Syntheses and Crystal Structures of Cobalt(Ⅱ) Complexes Constructed by Dipyrido[3,2-a:2',3'-c]phenazine and Different Carboxylate Ligands

Two new metal-organic complexes,{[Co2（bptc）（DPPZ）2（H2O）2]·H2O}n 1 and {[Co2（ccm）2（DPPZ）2]·2H2O}n 2,were obtained by the hydrothermal reactions of Co（NO3）2·6H2O with chelating ligand dipyrido[3,2-a：2＇,3＇-c]phenazine（DPPZ） and the corresponding carboxylic acid,namely,3,3＇,4,4＇-benzophenonetetracarboxylic acid（H4bptc） or 2-carboxycinnamic acid（H2ccm）,respectively.The complexes were structurally characterized by single-crystal X-ray diffraction,elemental analyses,IR spectra,and thermal gravimetry.1 presents unique chiral chain structures,which are further consolidated into three-dimensional supramolecular frameworks via noncovalent bonds,such as hydrogen bonding and π-π interactions.2 features infinite double-chain structures,which are connected by strong π-π interactions to result in three-dimensional supramolecular architectures.

Syntheses,Crystal Structures,and Magnetic Properties of Cobalt(Ⅱ) Complexes with 1,1-Cyclohexanediacetic Acid

Two new Co（Ⅱ） coordination polymers,{[Co_3（Hchda）_2（chda）_2（bpp）_2（H_2O）_2]}_n 1 and {[Co（chda）（bpe）（H_2O）]·3H_2O}_n 2（H_2chda = 1,1-cyclohexanediacetic acid,bpp = 1,3-bis（4-pyridinyl）propane and bpe = 1,2-bis（4-pyridinyl）ethylene）,were hydrothermally synthesized and then characterized by elemental analysis,IR spectroscopy,thermogravimetric analysis（TGA）,and single-crystal X-ray diffraction.Complex 1 possesses an infinite metal-organic layer based on triply bridged linear trinuclear subunits and complex 2 exhibits a square（4,4） grid layer with dangling lateral arms resulting from eight-membered rings above and below the layer.In addition,magnetic properties of complexes 1 and 2 are also given.

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, Crystal Structure, and Fluorescent and Thermal Stability Properties of Two New Cobalt(Ⅱ) Complexes with 2,2’-Bipy as Ligand

Two new cobalt（Ⅱ）complexes[Co2（2,2?-bipy）2（dpa）2（H2O）5]·4H2O（1）and Co（2,2?-bipy）3（SO4）]·7.5H2O（2）have been synthesized with diaphonic acid（H2dpa）and 2,2?-bipyridine（2,2?-bipy）as ligands.In 1,two neighboring cobalt（Ⅱ）ions are linked together by one bridging diaphonic acid group,forming an asymmetric dinuclear structure.1 crystallizes in triclinic,space group ■ with a=9.825（6）,b=13.007（8）,c=19.586（1）?,α=80.773（1）o,β=77.065（1）o,γ=85.902（1）o,Mr=431.4,V=2406.5（3）?3,Dc=1.48 g/cm3,Z=2,μ（MoKα）=0.767 mm-1,F（000）=1112,the final R=0.0379 and wR=0.0862.The central cobalt（Ⅱ）ions in 1 and 2 are coordinated with six atoms,forming distorted octahedral coordination geometry.The fluorescence and thermal stability properties of 1 and 2 are also reported.

Cobalt Schiff base complexes: Synthesis characterization and catalytic application in Suzuki–Miyaura reaction

3-Methoxysalicylaldehyde was condensed with the amines 4-aminoacetophenone and 2-amino-5-bromopyridine to obtain Schiff base ligands, 1 and 2, which were coordinated to cobalt salts as complex 1 and complex 2, respectively. The synthesized ligands and complexes were characterized by spectroscopic(FT-IR,UV–Vis,~1H-NMR and mass spectrometry), thermal(TGA) and elemental analysis. The structures of the complexes were verified by evaluating their magnetic susceptibility and spectroscopic evidences. Synthesized complexes were studied for their catalytic activity in the Suzuki–Miyaura cross-coupling of aryl halides with phenylboronic acid. Optimized reaction yields 90% of the cyanobiphenyl for complex 1 and 91% for complex 2 with 0.1 mmol of catalyst loading thereby substantiating the C\\C coupling efficiency of the synthesized complexes, 1 and 2.

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.

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

Synthesis,Structure,Fluorescent Property and Natural Bond Orbital(NBO) Analysis of a One-dimensional Cobalt(III) Complex Containing 1,3-Benzenedicarboxylate and 2-Methyldipyrido[3,2-f:2',3'-h]quinoxaline Ligand

A novel metal-organic coordination polymer [Co（m-BDC）（Medpq）·2H2O]n（m-H2BDC = benzene-1,3-dicarboxyalic acid,Medpq = 2-methyldipyrido[3,2-f：2＇,3＇-h]quinoxaline） has been hydrothermally synthesized and structurally characterized by elemental analysis,IR spectrum and single-crystal X-ray diffraction.The title compound crystallizes in monoclinic,space group C2/c with a = 19.986（4）,b = 15.789（3）,c = 16.292（3）（A°）,β = 126.54（3）°,V = 4130.3（14）（A°）^3,C23H18N4O6Co,Mr = 505.34,Dc = 1.625 g·cm^-3,Z = 8,μ = 0.883 mm^-1,F（000） = 2072,the final R = 0.0772 and wR = 0.1428.The crystal structure of complex 1 is an infinite zigzag-like chain of hexacoordinate Co^3＋ ions,in which the Co^3＋ ions are bridged in two coordination modes by m-BDC^2＋ ligands and decorated by Medpq ligands,showing a slightly distorted octahedral geometry.Additionally,the compound shows strong fluorescence in the solid state at room temperature.Natural bond orbital（NBO） analysis is performed by using the NBO method built in Gaussian 03 Program.The calculation results show a covalent interaction between the coordinated atoms and Co^3＋ ions.

Catalytic Effect of Cobalt and Iron Complexes Incorporating Bis(2-aldiminoethyl)amine Ligands on Ethylene Oligomerization

Complexes [MCl 2{CH 3N(CH 2CH 2N[CDS1]CR 1R 2) 2}]((3, M=Co, R 1=H, R 2=Ph ; 4, M=Fe, R 1=H, \{R 2=Ph\}; 5, M=Co, R 1=R 2=Ph) were prepared and characterized by IR spectra and elemental analysis. The combination of each of complexes 3-5 with ethylaluminoxane(EAO), respectively, was found to be moderately active for ethylene oligomerization to low carbon olefins. The activity of 113 kg oligomers·mol -1 Co·h -1 for complex 3(100 mol of EAO, 180 ℃ and 1 8 MPa ethylene) was observed with a selectivity of 93% to C 4-10 olefins, of which 96% were linear C4 10 olefins. The catalytic properties of complexes 3-5 were compared with those of analogous P,P coordinated complexes [MCl 2{CH 3N(CH 2CH 2PPh 2) 2}](1, M=Co; 2, \{M=\}Fe).

Synthesis and Crystal Structure of Cobalt(Ⅱ) and Copper(Ⅱ) Complexes Involving L-Aamino Alcohols

Two novel L-amino alcohol coordination cobalt and copper complexes I and Ⅱ were obtained separately from the direct reaction of L-plenylglycinol with Co（Ⅱ） acetate tetrahydrate in anhydrous ethanol and L-leucinol with Cu（Ⅱ） chloride dihydrate in anhydrous methanol. The structures of I and Ⅱ were determined by single-crystal X-ray diffraction and further characterized by elemental analysis and IR. For I： [Co3（C51H66N3O16）]2（OAc）, monoclinic, space group P21, a = 15.022（3）, b = 14.242（3）, c = 28.922（6） A, β = 98.944（4）°, V = 6112（2） A3, Z = 4, Dc = 1.339 g/cm^3, the final R = 0.0860 for 21906 observed reflections with I 〉 2（I）. For Ⅱ： Cu2[C24H58N4O7Cl]Cl, orthorhombic, space group P212121, a = 6.1861（13）, b = 20.838（4）, c = 28.274（6） , V = 3644.6（13） 3, Z = 4, Dc = 1.310 g/cm^3, the final R = 0.0642 for 11106 observed reflections with I 〉 2（I）. The complexes were then used to catalyze the Henry reaction and catalytic activity determined by 1H NMR.

Syntheses and Structures of Two New Cobalt Supramolecular Complexes, [Co(4,4'-bipy)_2(H_2O)_4]·[Co_2(4,4'-bipy)_3(H_2O)_8]·2TST·2(4,4'-bipy)·4H_2O and [Co(4,4'-bipy)_2(H_2O)_4]DSNT·4,4'-bipy

Two new cobalt（II） supramolecular complexes [Co（4,4＇-bipy）2（H2O）4]·[Co2（4,4＇-bipy）3（H2O）8]·2TST·2（4,4＇-bipy）·4H2O 1 and [Co（4,4＇-bipy）2（H2O）4]DSNT·4,4＇-bipy 2 based upon the assembly of Co（II）, 4,4＇-bipyridine （4,4＇-bipy） and two new multifunctional organic ligands, 2,4,6-tris（4-sulfophenyl- amino）-1,3,5-triazine （H3TST） and 2,4-bis（p-sulfanilato）-6-diethylamino-1,3,5-triazine （H2DSNT）, have been prepared by hydrothermal method and characterized by elemental analysis, IR spectrum, and single-crystal X-ray diffraction. The crystal structure of 1 is of monoclinic, space group P21/n with a = 13.599（4）, b = 18.988（6）, c = 22.995（7） A, β = 90.273（6）°, V = 5938（3）A^3, Z = 4, C56H59Co1.5N13O17S3, Mr = 1370.74, Dc = 1.533 g/cm^3, μ = 0.613 mm^-1, F（000） = 2842, GOOF = 1.018, the final R = 0.0796 and wR = 0.1498 for 9019 observed reflections with I 〉 2σ（I）. The crystal structure of 2 belongs to the monoclinic system, space group C2/c with a = 18.864（6）, b = 14.283（5）, c = 20.246（7）A, β = 107.799（6）°, V = 5194（3）A^3, Z = 4, C49H52CoN12O10S2, Mr = 1092.08, Dc = 1.397 g/cm^3, μ = 0.480 mm^-1, F（000） = 2276, GOOF = 1.059, the final R = 0.0665 and wR = 0.1900 for 4887 observed reflections with I 〉 2σ（I）. The results of X-ray crystal structure analysis revealed that complexes 1 and 2 exhibit layered supramolecular frameworks stabilized by electrostatic interactions, π-π interactions and hydrogen bonds.

Water oxidation catalytic ability of polypyridine complex containing a μ-OH, μ-O_2 dicobalt(iii) core

Two polypyridine complexes containingμ‐OH,μ‐O2dicobalt(III)cores,[(TPA)CoIII(μ‐OH)(μ‐O2)CoIII(TPA)](ClO4)3and[(BPMEN)CoIII(μ‐OH)(μ‐O2)CoIII(BPMEN)](ClO4)3(TPA=tris(2‐pyridylmethyl)amine,BPMEN=N,N′‐dimethyl‐N,N′‐bis(pyridin‐2‐ylmethyl)ethane‐1,2‐diamine),have previously been reported as inactive in the light‐driven water oxidation reaction(ACS Catal.,2016,6,5062?5068).Herein,another dicobalt(III)compound,μ‐OH,μ‐O2‐[{(enN4)2Co2}](ClO4)3(enN4=1,6‐bis(2‐pyridyl‐2,5‐diazaocta‐2,6‐diene),with a similar core structure was synthesized,characterized,and applied to the light‐driven water oxidation reaction.Collective experiments showed that the complex itself was also inactive in the light‐driven water oxidation,and that the activity observed originated from Co(II)impurities.This research establishes that complexes possessing aμ‐OH,μ‐O2dicobalt(III)core structure are not appropriate choices for true molecular catalysts ofwater oxidation.

Syntheses and Crystal Structures of Cobalt(II) Chloride Complexes of 1,3-Bis(pyridyl-4-ylthio)propan-2-one

Reactions of 1,3-bis（pyridyl-4-ylthio）propan-2-one L and COCl2·6H2O under different conditions gave two new cobalt（Ⅱ）-chloride-L complexes with distinct structures. Complex [Co（L）2Cl2]·0.5CH3OH}n 1 prepared by solvothermal treatment is a 3D network, whereas complex {[Co3（L）2Cl6（DMF）4]·2CH3OH·H2O} 2 obtained in DMF-diethyl ether system is a discrete acyclic trimer. Crystal data for 1： space group lbca, a = 15.993（4）, b = 18.454（5）, c = 21.506（6）A, V= 6347（3） ,A^3, Z = 8, Dc = 1.462 g/cm^3,μ = 1.005 mm^-1, F（000） = 2864, C26.5H26Cl2CoN4O2.5S4, Mr = 698.58, the final R = 0.0499 and wR = 0.1024. Crystal data for 2： space group P1^-, a = 9.9177（6）, b = 11.0871 （4）, c = 15.5490（12） ,A, α = 83.1834（14）,β = 88.910（13）, γ = 71.096（ 11 ）°, V = 1605.8（2） A^3, Z = 1, Dc = 1.362 g/cm^3,μ= 1.194 mm^-1, F（000） = 677, C40H62Cl6Co3N8O9S4, Mr = 1316.71, the final R = 0.0666 and wR =0.1575.

STUDY ON BINUCLEAR COPPER(I)COMPLEXES III.SYNTHESIS,CHARACTERIZATION AND ELECTROCHEMISTRY OF DICHLORO-TRIS(4-VINYLPYRIDINE)-DICOPPER(I)COMPLEX

Recent years,many novel complexes have been prepared by using hetero-bidentate ligands.However,complexes with such ligands as 4-vinylpyridine which has two different coordinating sites have not been reported,and only a few complexes of Cu(I)have been published^(1-3).The title complex Cu_2(C_5H_4N·CH=CH_2)_3Cl was prepared and characterized by elemental analyses,ICP,IR,and electronic spectra.Its conductivity,oxidation potential and reduction potential were measured.

Synthesis, structural and spectroscopic characterization of the bis(nitrito-<i>N</i>) octaethylporphyrin cobalt(III) complex

The bis(nitrito-N) cobalt(III) octaethylporphyrin derivative with the formula [K(18-C-6)(NO2)0.5(H2O)0.5]2 [CoIII(OEP)(NO2)2] (1) (OEP = octaethylporphyrin and 18-C-6 is the crown ether18-crown-6) has been synthesized and characterized by UV-vis, IR and proton NMR spectroscopy which indicate, inter alia, that the cobalt ion presents the oxidation state III. The synthesis utilizes 18-crown-6 to solubilize potassium nitrite in the synthetic procedure. This compound crystallizes in the triclinic system, with the centric space group P-1 and the following unit cell parameters: 11.6724(2) ?, b = 12.5715(2) ?, c = 13.4722(3) ?, α = 101.1290(6)°, β = 106.6498(6)°, γ= 109.1507(6)°, Z = 1 and V = 1696.74(5) ?3. The crystal structure has been solved and refined to R = 0.0499 and R(w) = 0.1319. The X-rays molecular structure of 1 shows that there is a relatively close interaction of both two NO2- axial ligands of the ion complex [CoIII(OEP)(NO2)2]- with the potassium atoms of the two counterions [K(18-C-6) (NO2)0.5(H2O)0.5]0.5+. The title compound exhibits one-dimension polymer-like structure where “monomers” are linked together through strong O(H2O)—H…O(nitrito-O) hydrogen bonds.

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.

FERROMAGNETICALLY COUPLED Gd(III)Cu(II)Gd(III)TRINUCLEAR COMPLEXES

Three new heterotrinuclear complexes have been synthesized and characterized, namely {[Gd(L)(2)](2)[Cu(pbaOH)]}(ClO4)(4), where pbaOH denotes 2-hydroxy-1,3-propylenebis(oxamato), L stands for 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO2-phen) or 2,2'-bipyridyl (bpy). The temperature dependence of the magnetic susceptibility of ([Gd(phen)(2)(ClO4)](2)[Cu(pbaOH)])(ClO4)(2) has been studied in the 4-300K range, giving the exchange integral J = 6.69 cm(-1). This indicates a weak ferromagnetic interaction between the copper(II) and gadolinium(III) ions.