Effect Of Auxiliary Ligands Research Articles

Effect of Auxiliary Ligands on the Architectures of Manganese Complexes Constructed by N-Heterocyclic Ligands: Syntheses, Structures, and Properties

Two manganese complexes based on N-heterocyclic ligands, [Mn(bqdca)(2,2'-bipy)(H2O)2]n (1), Mn0.5(4,4'-bipy) (H2O)2?0.5bqdca?2H2O (2) (H2bqdca = 2, 2'-biquinoline-4, 4'-dicarboxylic acid, 2, 2'-bipy = 2, 2'-bipyridine, 4, 4'-bipy = 4, 4'-bipyridine), have been synthesized by hydrothermal methods based on Pearson?s acid-base theory and structurally characterized. In Complex 1, the Mn ions are bridged by bqdca2- anions to form one-dimensional chains, which are further linked by hydrogen bonds to generate a two-dimensional layered structure. In Complex 2, each Mn ion was coordinated by 4, 4'-bipy and water molecules to generate a mononuclear structure accompanied by bqdca2- anion balancing valences. The intermolecular hydrogen bonds can link them to construct a three-dimensional supramolecular structure. The different structures of Complexes 1 and 2 illustrate the great influence of the N-heterocyclic auxiliary ligands on the self-assembly of coordination architectures. 2,2'- bipy and 4,4'-bipy ligands all act as terminal ligands. In addition, Complexes 1 and 2 exhibit the photoluminescent emission at 455 nm and 463 nm, and 455 nm and 465 nm in the solid state, respectively, which may be attributed to intraligand transitions. The redshifts of Complexes 1 and 2 may be due to the ligand-to-metal charge transfer, comparing to the H2bqdca ligand.. KEYWORDS :Crystal structure, Manganese complex, N-Heterocyclic ligand, Photoluminesce.

Iridium-(κ2-NSi) catalyzed dehydrogenation of formic acid: effect of auxiliary ligands on the catalytic performance.

The iridium(III) complexes [Ir(H)(Cl)(κ2-NSitBu2)(κ2-bipyMe2)] (2) and [Ir(H)(OTf)(κ2-NSitBu2)(κ2-bipyMe2)] (3) (NSitBu2 = {4-methylpyridine-2-yloxy}ditertbutylsilyl) have been synthesized and characterized including X-ray studies of 3. A comparative study of the catalytic activity of complexes 2, 3, [Ir(H)(OTf)(κ2-NSitBu2)(coe)] (4), and [Ir(H)(OTf)(κ2-NSitBu2)(PCy3)] (5) (0.1 mol%) as catalysts precursors for the solventless formic acid dehydrogenation (FADH) in the presence of Et3N (40 mol%) at 353 K has been performed. The highest activity (TOF5 min ≈ 3260 h-1) has been obtained with 3 at 373 K. However, at that temperature the FTIR spectra show traces of CO together with the desired products (H2 and CO2). Thus, the best performance was achieved at 353 K (TOF5 min ≈ 1210 h-1 and no observable CO). Kinetic studies at variable temperature show that the activation energy of the 3-catalyzed FADH process is 16.76 kcal mol-1. Kinetic isotopic effect (5 min) values of 1.6, 4.5, and 4.2 were obtained for the 3-catalyzed dehydrogenation of HCOOD, DCOOH, and DCOOD, respectively, at 353 K. The strong KIE found for DCOOH and DCOOD evidenced that the hydride transfer from the C-H bond of formic acid to the metal is the rate-determining step of the process.

The effect of auxiliary ligands on nitrite group linkage isomerization reaction in a series of nickel(II) complexes

The effect of auxiliary ligands on nitrite group linkage isomerization reaction in a series of nickel(II) complexes

Cobalt-Based Metal-Organic Frameworks for Adsorption of CO2 and C2 Hydrocarbons: Effect of Auxiliary Ligands with Different Functional Groups.

Recently, metal-organic frameworks (MOFs) have been investigated as potential materials for CO2 capture and light hydrocarbon storage/separation due to their high porosity, large surface area, and tunable skeleton structures. In this work, the six cobalt-based MOFs 1-6 were successfully synthesized under solvothermal conditions by a mixed-ligand strategy. 1 and 2 have the same framework structure with a topology of {42·5}2{44·510·67·76·8}, while the structures of the 3-6 frameworks are the same with a topology of {42·5}2{44·510·69·74·8}. The adsorption properties of these MOFs for CO2 and C2 hydrocarbons were then investigated, and the effect of the functional groups was discussed. The results revealed that the introduction of amino and bromo groups could effectively strengthen the adsorption performance.

Hydrothermal synthesis of three zinc(II) coordination polymers from 0D to 2D: Synthesis, structure, luminescence properties and effect of auxiliary ligand on their structural architectures

Three new coordination compounds, [Zn2(bppc)2(bdc)(H2O)2]·4H2O(1) [Zn4(bppc)2(o-bdc)2(ox)(H2O)2]n·2nH2O (2), [Zn2(bppc)(ox)1.5(H2O)2]n·3.5nH2O (3) (Hbppc = 2,6-bis(pyrazin-2-yl)pyridine-4-carboxylate, H2bdc = 1,4-benzenedicarboxylic acid, H2(o-bdc) = 1,2-benzenedicarboxylic acid, H2ox = oxalic acid), with different structural dimensionality (0D, 1D and 2D, respectively) have been hydrothermally synthesized and structurally characterized. Single crystal X-ray analysis revealed that compound 1 shows a dimer structure, compound 2 and 3 show one-dimensional ring chain structure and two-dimensional structure respectively. The structure differences of 1–3 show that the aromatic acid as auxiliary ligand have important influence on the final structures. Additionally, the luminescent properties of 1–3 have been investigated with fluorescent spectra in the solid state, and 1–3 display a strong fluorescent emission at room temperature and have potential applications as fluorescent-emitting materials.

Fine-tuning the effects of auxiliary ligands on two trigonal-bipyramid cobalt(ii) complexes exhibiting field-induced slow magnetic relaxation

Two trigonal-bipyramid cobalt(ii) complexes exhibit field-induced slow magnetic relaxation effects due to their auxiliary ligands.

The effect of auxiliary ligand on the mechanism and reactivity: DFT study on H2 activation by Lewis acid–transition metal complex (tris(phosphino)borane)Fe(L)

The crucial role of the auxiliary ligand in hydrogen activation is revealed by DFT studies for the LA–TM ferraboratrane complex.

Syntheses, crystal structures and luminescence properties of lanthanide-based coordination polymers constructed from a functionalized terpyridyl carboxylate ligand

Six families of new lanthanide coordination polymers, [Ln2(L)6(H2O)2]n·3nH2O (Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6), Ho (7), Er (8), Yb (9)), [Pr2(L)2(ox)2(H2O)4]n·9nH2O (10), [Pr2(L)2(glu)2(H2O)2]n (11), [Er2(L)2(glu)2]n (12), [Nd2(L)2(adip)2]n (13), [Ln2(L)2(1,2-bdc)2(H2O)2]n (Ln = Eu (14), Gd (15), Er (16)), (HL = 4′-(2-carboxyphenyl)-4,2′:6′,4′′-terpyridine, H2ox = oxalic acid, H2glu = glutaric acid, H2adip = adipic acid, H2(1,2-bdc) = benzene-1,2-dicarboxylic acid) were synthesized under hydrothermal conditions and characterized by elemental analysis, IR and single crystal X-ray diffraction. Compounds 1–9 are isomorphic 1D chain structures based on binuclear Ln(III) units. Compound 10 is a 1D chain, where L− ligands dangle on two sides of the Pr-ox zigzag chain. Compounds 11 and 12 exhibit distinct 2D-layer structures consisting of Ln2(COO)4 binuclear units. Compound 13 displays an appealing 3D network structure, where the auxiliary ligand H2adip plays a significant role in the self-assembly process. Compounds 14–16 present a 1D-chain structure which is extended to a 2D-supramolecular framework by means of weak interactions. The diverse structures further verify the potential of HL ligand in the preparation of coordination polymers with new structures and properties. The effects of auxiliary ligands and coordination modes of HL ligand on the crystal architectures are discussed. The solid-state luminescence and thermal stabilities of compounds 1–16 also were studied. Based on the luminescent properties, we have designed and constructed successfully a series of doped-lanthanide MOF by adjusting the co-doping ratio of Eu(III) and Tb(III) into the same framework as that of 1–9. Interestingly, the luminescent colors of the Eu(III)-doped Tb(III) compounds can be tuned with change of excitation wavelength. Moreover, white-light emission was achieved on excitation at 330 nm.

Regioselective Cis Insertion of DMAD into Au–P Bonds: Effect of Auxiliary Ligands on the Reaction Mechanism

The cis insertion of dimethyl acetylenedicarboxylate (DMAD, 2) into the Au–P bond of Au(SAr)(PAr′3) (1) occurs selectively at room temperature to give adduct 3, whose X-ray crystallographic analysis exhibits the predominant character of an alkenylphosphorus zwitterion complex. The first-order kinetics with respect to 1 and 2 and the large negative value of ΔS⧧ indicate that the reaction proceeds through the coordination of 2 to 1 followed by a concerted inner-sphere nucleophilic attack of PPh3 on the coordinated triple bond. In contrast, Au(Cl)(PPh3) (4) does not react with 2 even at 60 °C. However, the tricoordinated 16-electron complex Au(Cl)(PPh3)2 (5) quite successfully reacts with 2 to produce insertion product 6, demonstrating that two PPh3 ligands are required for the reaction.

Muconate bridged coordination polymers of Cu(II): Effect of auxiliary ligand on their structural architectures

Two coordination polymers [Cu2(2,2′-bpy)2(muco)2(H2O)2](H2O)2, (1) and [Cu(4,4′-bpy)(muco)(H2O)2], (2) [H2muco=trans,trans-muconic acid or 1,3-butadiene-1,4-dicarboxylic acid, 2,2′-bpy=2,2′-bipyridyl and 4,4′-bpy=4,4′-bipyridyl] have been synthesized by the reaction of muconate dianion with Cu(NO3)2·3H2O in presence of auxiliary ligands 2,2′-bpy and 4,4′-bpy respectively. Single crystal X-ray crystallographic structure determination reveals that 1 has one-dimensional (1D) structural motif and an extensive H-bonding pattern gives rise to 3D supramolecular network in the crystal of 1. On the contrary, 2 exhibits threefold interpenetrating three-dimensional (3D) net-work with CdSO4 topology. In the formation of these complexes, the auxiliary ligand has a vital role in directing the solid-state structure with defined topological network.

Effect of auxiliary ligands on cobalt(II) coordination polymers with 5-(imidazol-1-ylmethyl)isophthalate

The reactions of cobalt(II) salt with 5-(imidazol-1-ylmethyl)isophthalic acid (H2L) as a main ligand and 1,10-phenanthroline (phen), 2-(pyridin-2-yl)-1H-benzo[d]imidazole (pybim) or 1,2-di(pyridin-4-yl)ethylene (dpe) as auxiliary ligand by hydrothermal method lead to the formation of four new complexes [Co(L)(phen)]·2H2O (1), [Co(L)(pybim)(H2O)]·2H2O (2), [Co(L)(pybim)]·H2O (3) and [Co(L)(dpe)0.5] (4), among them 2 and 3 were obtained by changing the metal-to-ligand ratio. While in the absence of any auxiliary ligand, complex [Co(L)] (5) was obtained. The complexes 1–5 have been characterized by single crystal and powder X-ray diffractions, IR, elemental and thermogravimetric analyses. Complexes 1 and 2 have double- and single-chain structures, while 2 and 3 are 3-connected uninodal and (3,6)-connected binodal 2D networks with (63) and [(63)(66)] topology, respectively. All the complexes 1–4 show 3D supramolecular structures through hydrogen bonding/π–π interactions. Complex 5 shows a (5,5)-connected binodal 3D net with [(45)(65)] topology. The results imply that the auxiliary ligand as well as the metal-to-ligand ratio has great impact on the structure of the complexes.

Effect of auxiliary-ligand on assembly of lanthanide(III) complexes with quinoline-2-carboxylic acid: Synthesis, structure, photoluminescent and magnetic properties

A series of lanthanide complexes [Ln2(QUIN)6(H2O)6]·3H2O (Ln=Pr (1), Nd (2), Sm (3), Eu (4)), [Pr(QUIN)3(H2O)]n (5) and [Pr2(QUIN)4(phen)2(NO3)2(H2O)2] (6) were synthesized by hydrothermal reactions of corresponding lanthanide nitrates with quinoline-2-carboxylic acid (HQUIN) under intervention of auxiliary ligands, and characterized by elemental analysis, IR, TGA and single-crystal X-ray diffraction. Complexes 1–4 and 6 exhibit the dinuclear lanthanide architectures in which each Ln(III) ion is nine-coordinated and possesses distorted tricapped trigonal prism geometry. The dinuclear structures in 1–4 are further linked by the hydrogen bond interactions resulting in the formation of the two-dimensional supramolecular network, while the dinuclear structures in 6 form the three-dimensional supramolecular network. Complex 5 is composed of one-dimensional chain framework, which further pack into the two-dimensional layer through weak π⋯π stacking interactions. The supramolecular architectures 1–6 show that the numerous hydrogen bonds are responsible for the increasing thermal stability. Photoluminescence investigation reveals that complexes 4 and 6 display strong red and green emission, respectively. Moreover, the magnetic properties of 2 and 6 have also been investigated.

Substituted tridentate pyrazolyl ligands for chromium and nickel-catalyzed ethylene oligomerization reactions: effect of auxiliary ligand on activity and selectivity

Dois novos complexos de cromo(III) contendo ligantes tridentados [CrCl3(L)] (1a, L = bis[2-(3-fenil-1-pirazol)etil)]amina; 2a, L = bis[2-(3-metil-5-fenil-l-pirazol)etil]sulfeto) foram preparados e caracterizados por analise elementar. Apos ativacao com metilaluminoxano (MAO), estes pre-catalisadores mostraram altas frequencias de rotacao nas reacoes de oligomerizacao do etileno sob condicoes otimizadas (FRs = 22,9-36,4×103 mol C2H4 (mol CrIII)-1 h-1, [Cr] = 10,0 µmol, 80 oC, 20 bar de etileno, [Al]/[Cr] = 300, tempo de oligomerizacao = 20 min), produzindo olefinas-α no intervalo de C4-C14+ com alta seletividade (67,71-73,47%). Os desempenhos cataliticos sao afetados substancialmente pelos grupos presentes nos ligantes, especialmente os substituintes nas posicoes 3 e 5 dos aneis pirazol. Em paralelo, o emprego de complexos de niquel(II) tais como NiCl2{bis[2-(3,5-dimetil-1-pirazol)metil]benzilamina} (3) e NiCl2{bis[2-(3,5-dimetil-1-pirazol)etil)]eter} (5) em reacoes de oligomerizacao conduzidas na presenca de trifenilfosfina (PPh3) resultou em sistemas cataliticos altamente ativos com frequencias de rotacao (FRs) variando de 36,4 a 154,2×103 mol C2H4 (mol NiII)-1 h-1. A presenca deste ligante auxiliar tem um impacto significativo na producao seletiva de olefinas-α, diminuindo substancialmente a quantidade de buteno-1 com concomitante aumento da quantidade das fracoes de butenos-2. Tentativas de cristalizacao do complexo de niquel 3 resultaram na formacao de um composto de niquel tetrametalico [{(L)(µ3-Cl)NiCl}4] (4, L = 1-anilinometil-3,5-dimetil-1-pirazol) o qual foi caracterizado por difratometria de raios X.

The effects of auxiliary ligands on the synthesis, crystal structures and properties of three complexes with a substituted pyridazine ligand

Three new complexes, [Co(L)2(SCN)2] (1), [Co2(L)4(μ-N3)2](ClO4)2(H2O)1.5 (2), and [Ni(L)3](ClO4)2(CH3OH)2 (3), have been synthesized and structurally characterized, where L is 3-(3′,5′-dimethyl-pyrazole)-6-Cl-pyridazine. Single crystal X-ray analyses show that all three complexes crystallize in the monoclinic crystal system. In complex (1), the Co(II) atom is in a distorted octahedral environment consisting of four nitrogen atoms from two ligands and two nitrogen atoms of SCN−, which is further extended into a 1D chain by intermolecular hydrogen bonds. Two Co(II) atoms in complex (2) are linked by two azide anions in a μ-1,1 mode to make a binuclear structure. Without any auxiliary ligand, the Ni(II) atom in complex (3) adopts a distorted octahedral geometry involving six nitrogen atoms from three ligands. The electronic absorption spectra of the title compounds are discussed as well. The effects of auxiliary ligands on the structures and properties of the title complexes have been studied and discussed. Three new complexes, [Co(L)2(SCN)2] (1), [Co2(L)4(μ-N3)2](ClO4)(H2O)1.5 (2) and [Ni(L)3](ClO4)2(CH3OH)2 (3), have been synthesized and structurally characterized, where L is 3-(3′,5′-dimethyl-pyrazole)-6-Cl-pyridazine. Complexes (1) and (3) are mononuclear compounds, which are different from the binuclear complex (2). Auxiliary ligands are the main reasons that results in the different structures of the title complexes and their different fungicidal activities.

Topological Diversification in Metal‐Organic Frameworks: Secondary Ligand and Metal Effects

AbstractA series of interesting coordination polymers have been prepared by the combination of a V‐shaped 4,4′‐oxybis(benzoic acid) (H2oba) and neutral organonitrogen ligands with different metal ions, namely, {[M(oba)(bpe)]·H2O}n [M = Mn (1), Co (2)], [M(oba)(N3)]n [N3 = dipyridin‐2‐ylamine; M = Cd (3), Cu (4)] and {[Zn(oba)(N5)]·2H2O}n (5) [bpe = 1,2‐bis(4‐pyridyl)ethene, N5 = bis(pyridin‐2‐yl)pyridine‐2,6‐diamine]. The framework structures of these neutral polymeric complexes have been determined by single‐crystal X‐ray diffraction studies. Compound 1 has a threefold pcu‐type network structure. Although 2 has the same ligands and coordination modes as 1, it consists of corrugated 2D layers formed of a series of squares, which allows the sheets to interpenetrate in an unusual 2D → 3D parallel fashion. Polymers 3 and 4 exhibit double‐helical chains formed by π–π stacking interactions from the phenyl rings of the N3 ligands. Compound 5 forms a 2D supramolecular architecture directed by hydrogen bonding between the NH groups of the N5 ligand, the uncoordinated carboxylate oxygens, and the intercalated water molecules. This work markedly indicates that the effect of auxiliary ligands is significant in the construction of these network structures, which are also well regulated by the metal centers. Thermogravimetric analysis (TGA) and XRPD results for compound 1 as well as luminescent properties for compounds 3 and 5 are discussed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Palladacycles with a Metal‐Bonded sp3‐Hybridized Carbon as Intermediates in the Synthesis of 2,2,3,4‐Tetrasubstituted 2H‐1‐Benzopyrans and 1,2‐Dihydroquinolines. Effects of Auxiliary Ligands and Substitution at a Palladium‐Bonded Tertiary Carbon.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Palladacycles with a Metal-Bonded sp3-Hybridized Carbon as Intermediates in the Synthesis of 2,2,3,4-Tetrasubstituted 2H-1-Benzopyrans and 1,2-Dihydroquinolines. Effects of Auxiliary Ligands and Substitution at a Palladium-Bonded Tertiary Carbon

Prompted by the failure to prepare stable oxapalladacycles L2Pd-1-C6H4-2-OC(R1)COOEt with PPh3 ligands (L = PPh3) and substituents R1 other than hydrogen, systematic studies on the effects of steric and electronic properties of auxiliary ligands L and substituents R1 (alkyl, aryl) on the feasibility of formation, stability, and reactivity of the oxapalladacycles were performed. Using N,N,N‘,N‘-tetramethyl-1,2-ethylenediamine bidentate ligand (L−L = TMEDA), stable palladacycles featuring substituents R1 (Me, Et, i-Pr, and Ph) were prepared, and the presence of palladium-bonded tertiary sp3-hybridized carbons was confirmed by X-ray crystallographic analyses on palladacycles with i-Pr and Ph substituents R1. Relying on 31P NMR analyses of crude reaction mixtures, ligand displacement reactions of palladacycles (TMEDA)Pd-1-C6H4-2-OC(R1)COOEt with monodentate phosphines (PPh3 and PPh2Me) were studied, as well as base-mediated ring-closure reactions of arylpalladium(II) iodo complexes (PPh3)2Pd(-1-C6H4-2-OCHR1COOEt)I and (PPh2Me)2Pd(-1-C6H4-2-OCHR1COOEt)I. In both series, higher conversions to corresponding palladacycles L2Pd-1-C6H4-2-OC(R1)COOEt were achieved with PPh2Me ligands, and both the transformations were negatively affected by an increase in the steric bulk of substituents R1. Although the palladacycles with monodentate phosphines could not be isolated as stable entities, IR spectroscopic analyses supported the presence of a Csp3−Pd bond. On the basis of these studies, a one-pot conversion of stable arylpalladium(II) iodo complexes with PPh2Me ligands into 2,2,3,4-tetrasubstituted 2H-1-benzopyrans and 1,2-dihydroquinolines via the insertion of unsymmetrical alkynes into in situ formed palladacycles was developed, providing the heterocycles in good yields (44−80%) as single regioisomers.