Structure and magnetism of mono-, di-, and trinuclear benzoato cobalt(II) complexes

Three cobalt(II) - benzoato (bz) complexes have been prepared and structurally characterized. In the mononuclear complex trans-[Co(bz)₂(H₂O)₂(nca)₂] the benzoato ligand is unidentate (nca = nicotinamide). The dinuclear complex [(μ₂-bz)₄{Co(qu)}₂] is a structural analog of the copper acetate (qu = quinoline) where four bidentate benzoato ligands link two cobalt(II) pentacoordinate centers. The trinuclear complex of the composition [Co₃(bz)₆(inca)₆] contains a central hexacoordinate {(bz)₂Co(inca)₂(bz)₂} unit in which the bidentate benzoato ligands held the central and peripheral cobalt(II) centers (inca = iso-nicotinamide); the peripheral hexacoordinate {(bz)Co(inca)₂<} units contain the terminal benzoato ligand in its bidentate function. The magnetic susceptibility data down to T = 2 K and the magnetization data up to B = 7 T reveal a considerable magnetic anisotropy due to the single-ion zero-field splitting.     

Synthesis,crystal structure,spectroscopy and magnetism of a trinuclear nickel(II) complex with 3,5-pyrazoledicarboxylic acid as bridge ligands

A new complex of [Ni₃(dcp)₂(H₂O)₁₀] (1) (H₃dcp = 3,5-pyrazoledicarboxylic acid) has been synthesized from H₃dcp and Ni(NO₃)₂·6H₂O by hydrothermal reaction. Complex 1 has the discrete trinuclear structure. Three Ni(II) ions are bridged by two dcp³⁻ ligands, with 10 coordinated water molecules as terminal ligands. The molecules of [Ni₃(dcp)₂(H₂O)₁₀] extend into three-dimensional supramolecular architectures by intermolecular O–H···O hydrogen bonds as well as π-π stacking interactions. Magnetic susceptibility measurement shows that a weak antiferromagnetic interaction is operative between nickel(II) ions and an excellent simulation of the experimental data gives D = 5.27 cm⁻¹, J = −2.19 cm⁻¹ and g = 2.05.     

A binuclear copper(II) complex with unusual magnetism

A binuclear copper(II) complex [Cu₂ (μ-pyo)₂Br₄] _n (where pyo = pyridine N-oxide) has been synthesized and its structure determined by X-ray crystallography. This complex crystallizes in monoclinic, space group P2₁/c, with unit cell dimensions a = 11.020(3) Å, b = 10.049(3) Å, c = 7.905(2) Å, β = 110.609(3)°, and Z = 2. The structure was refined to final R = 0.0311 and wR = 0.0721 for 1302 observed reflections (I > 2σ(I)). In the complex, two Cu(II) ions are bridged by two pyo ligands and four bromides coordinate the Cu(II); the distance between the bridged Cu(II) ions is 3.261 Å. The variable-temperature (4–300 K) magnetic susceptibility data show that the magnetic moment is zero. Thus, there exists very strong anti-ferromagnetic coupling between the bridged binuclear Cu(II) ions. Density functional calculations yield a singlet-triplet splitting 2J = ?1355 cm^?1.     

Synthesis,crystal structure and magnetism of a two-dimensional Ni(II) coordination polymer with thiocyanate anion and dehydrogen-1,10-phenanthrolin-2-ol as bridging ligands

A two-dimensional coordination polymer [Ni(μ_1,3-SCN)(μ-Pheno)(CH₃OH)] _n (where Pheno = dehydrogen-1,10-phenanthrolin-2-ol) has been synthesized and its crystal structure determined by X-ray crystallography. Adjacent Ni(II) ions are coordinated by μ_1,3-SCN^? and μ-Pheno alternately forming a two-dimensional sheet structure. The fitting of the variable-temperature magnetic susceptibilities with a binuclear nickel(II) formula reveals that there is an anti-ferromagnetic interaction between the bridging Ni(II) ions with the magnetic coupling constant 2J = ?0.67 cm^?1.     

Synthesis,crystal structure and magnetism of a three-dimensional Mn(II) coordination polymers with 2,5-dimethylpyrazine-1,4-dioxide as bridging ligand

A novel three-dimensional Mn(II) coordination polymer, {[Mn(μ_1,6-dmpzdo)₃]?·?(ClO₄)₂} _n , has been synthesized with 2,5-dimethylpyrazine-1,4-dioxide (dmpzdo) as a bridging ligand and its crystal structure determined by X-ray crystallography. The complex crystallizes in a trigonal system with a space group R-3 and a?=?11.6672(14), b?=?11.6672(14), c?=?16.652(4)?Å. In the complex each Mn(II) is coordinated by six μ_1,6-dmpzdo bridging ligands and each μ_1,6-dmpzdo bridging ligand coordinates two Mn(II) ions, forming a three-dimensional structure. The variable temperature (4–300?K) magnetic susceptibility data gave the magnetic coupling constant 2J?=??0.30?cm^?1.     

Synthesis,crystal structure and magnetism of 1D cobalt(II) coordination polymer with thiocyanate as bridging ligand

A one-dimensional coordination polymer [Co(μ _1,3-NCS)₂(npdo)₂] _n (npdo?=?4-nitropyridine N-oxide) has been synthesized and structurally determined by X-ray crystallography. The complex crystallizes in the orthorhombic space group of Pbcn with a?=?22.688(5)?Å, b?=?7.2636(17)?Å, c?=?10.299(2)?Å. Adjacent Co(II) ions are coordinated by two μ _1,3-SCN^? bridging ligands, forming a one-dimensional chain along the c axis and the npdo coordinates to Co(II) ion as a terminal ligand. The thermal variation of the magnetic moments of the complex reflects the antiferromagnetic interaction between the bridged Co(II) ions above 20?K and the ferromagnetic transition or the strong short-range spin interaction below 20?K.     

Syntheses,crystal structures,and magnetism of two phenylacetate imidazolate copper(II) complexes

The influence of pH for the reaction system involving CuCl₂?·?2H₂O, imidazole (Him) and phenylacetic acid (HL) at room temperature was investigated. Cu₂(Him)₄L₄?·?2H₂O (1) and Cu₃(Him)₂(im)₂L₄ (2) were synthesized at pH 6.5 and 7.5, respectively. In 1, the Cu is coordinated by two nitrogen atoms of two Him and three oxygen atoms from three phenylacetates to form a square pyramid CuN₂O₃. Adjacent square pyramids share edges to form Cu₂N₄O₄ dimers, which are assembled by hydrogen bonds into a 2-D layer parallel to the (001) plane. In 2, copper atoms are interlinked by im^? and L^? to form a 2-D layer parallel to (100). The resulting layers have C–H···O hydrogen bonds leading to a 3-D supramolecular architecture. Variable temperature magnetism of 1 and 2 suggests a weak ferromagnetic or antiferromagnetic coupling exchange (J?=?0.58?cm^?1 for 1, J?=??10.24?cm^?1 for 2).     

Hydrothermal Synthesis and Structure of a Novel 1-D Mn(II) Compound with Carboxlyto and Imidazole Ligands

1 INTRODUCTION Mn complexes containing carboxylato ligands attract considerable interest due to the richness in structural chemistry[1～4] and potential applications in catalysis[5, 6], for example, some highly efficient Mn catalase mimics[7, 8]. Recently, we focus on the hy- drothermal synthesis of manganiferous coordination polymers using multiple carboxylato and nitrogen- containing ligands[9, 10]. As one of the interesting bridge ligands, terephthalato ligand (ta) can provide multipl…     

A New Maleato-Bridged Mn(II) Phen Complex: Structure and Magnetic Properties of Mn(phen)(C4H2O4)

Reaction of freshly-precipitated MnCO₃, phenanthroline monohydrate and maleic acid in CH₃OH/H₂O (pH = 6.23) at 50°C afforded a new maleato bridged, catenated coordination polymer Mn(phen)(C₄H₂O₄), where the Mn atoms are each octahedrally coordinated by two N atoms of one phen ligand and four O atoms of three maleato ligands (d(Mn-N) = 2.300, 2.331 Å; d(Mn-O) = 2.112-2.207 Å). The maleato ligand chelates one Mn atom to form a seven membered ring while two carboxylate groups of different maleato ligands bridge two Mn atoms to form an eight-membered ring, 1D ¹ _∞[Mn(phen)(C₄H₂O₄)_3/3] chains being generated in a sequence of seven- and eight-membered rings. Significant interchain π-π stacking interactions are responsible for the supramolecular assembly of the polymeric ¹ _∞[Mn(phen)(C₄H₂O₄)_3/3] chains into 2D layers. At low temperatures, the title complex becomes antiferromagnetic with T _Née1 = 7 K and follows the Curie-Weiss law _χm (T + 9.82) = 4.140 cm³ mol^-1 K between 30-300 K.     

Synthesis and studies of a trinuclear Mn(II) carboxylate complex

We report a carboxylate triangle consisting of three manganese(II) centres which is made from manganese(II) carbonate and pivalic acid. The magnetic exchange within the triangle is extremely weak, and antiferromagnetic. Several models have been used to fit the magnetic data, and the best fit uses two weak antiferromagnetic coupling constants of J(1)=-0.588 cm(-1) and J(2)=-0.855 cm(-1). Exchange interactions between the metal centres has been calculated using DFT adopting all the three possible Heisenberg models for a trinuclear system and the results are compared with experimental values. Spin density distribution is used to analyse the nature of the coupling between the metal centres. EPR spectroscopy has been used to explore the nature of the ground state. Recrystallisation of the trinuclear compound from MeCN gives a polymer, while oxidation in air leads to a known compound--an edge-sharing bitetrahedral (MnIII2MnII4) cage.     

A new 2D Mn(II) coordination polymer constructed from carboxylate and N-donor coligand: Synthesis,structure, and magnetism

A new complexes, namely, {[Mn₂(L)₂(Bipy)₂] · H₂O} _n (I) (H₂L = diphenic acid, Bipy = 4,4′-bipyridine) has been synthesized and structurally characterized by single-crystal diffraction analysis. In I, the two syn, anti-carboxylate groups in L bridge Mn(II) forming a one-dimensional chain, which is further connected by Bipy into 2D double layer. Magnetic study reveals the overall antiferromagnetic interaction between neighboring Mn²⁺ ions in compound I.     

Synthesis and magnetism of 2-hydroxy-1,3-propanediylbis-(oxamato) bridged trinuclear copper(II) complexes

Summary Four novel trinuclear copper(II) complexes have been synthesized, namely {[Cu(pbaOH)][Cu(L)]₂}(ClO₄)₂, where pbaOH = 2-hydroxy-1,3-propanediylbis(oxamato) and L is 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO₂-phen), 2,2-bipyridyl (bipy) or 4,4-dimethyl-2,2-bipyridyl (Me₂bipy). Based on i.r. and electronic spectra, elemental analyses, and conductivity measurements oxamato-bridged structures consisting of three copper(II) ions, in which each copper(II) ion has a square-planar environment, are proposed. The temperature-dependent magnetic susceptibility of {[Cu-(pbaOH)][Cu(phen)]₂}(ClO₄) ₂ has been studied in the 4.2–300 K range, giving the exchange integral J=- 111.9cm^–1. The result revealed the operation of an antiferromagnetic spin-exchange interaction between adjacent copper ions.     

Synthesis, structure and magnetic properties of a trinuclear [Mn(III)Mn(II)2] single-molecule magnet

Ferromagnetic exchange between the three Mn ions in the complex [Mn3(Hcht)2(bpy)4](ClO4)3 leads to a spin ground state of S = 7; single crystal studies reveal the temperature and sweep rate dependent hysteresis loops expected for a single-molecule magnet.     

Structure of a new trinuclear nickel(II) complex with a salen-type bisoxime ligand

A new trinuclear Ni(II) complex {[NiL(DMF)]₂(OAc)₂Ni}·2DMF (H₂L = 4,4′-dichloro-2,2′-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol) is synthesized and characterized by elemental analyses, IR spectra, UV-Vis spectra and X-ray crystallography. The results show that the Ni(II) complex consists of three Ni(II) ions, two tetradentate (μ-L)^2? units, two coordinated μ-acetate ions, two coordinated DMF molecules, and two crystallization DMF molecules. All hexacoordinated Ni(II) ions of the complex have a slightly distorted octahedral geometry. The crystal packing of the Ni(II) complex reveals a notable feature of this structure: the formation of an infinite supramolecular 2D layered structure by virtue of intermolecular C-H…O hydrogen bonding.     

Structure and magnetism of Co(II) complexes with bidentate heterocyclic ligand Hsalbim derived from benzimidazole

Two mononuclear Co(II) complexes based upon 2-(1H-benzimidazol-2-yl)phenol, abbreviation Hsalbim ligand, have been prepared and studied. The structure of Hsalbim and [Co(salbim)₂] have been confirmed by X-ray structure analysis. The second cobalt(II) complex matches the formula [Co(salbim)₂]·(Hsalbim)·MeOH assuming a co-crystallization of one neutral ligand. The electronic spectra are consistent with the tetrahedral pattern. Magnetic susceptibility measurements down to T = 2 K along with the magnetization data until B = 7 T show that the Co(II) complexes are high-spin with a considerable zero-field splitting of the ⁴B₁(D_2d) term: D/hc = 67 and 55 cm⁻¹, respectively.     

Coordination polymer incorporating cobalt(II) and glycine acid: structure and magnetism

We report the structure and magnetism of a cobalt(II) compound with glycine acid, Co(C₂H₄NO₂)₂ · H₂O (1). It crystallizes in the orthorhombic system, space group P2(1)2(1)2(1) with a = 5.2301(10) Å, b = 10.837(2) Å, c = 13.542(3) Å, R ₁ = 0.0448, wR ₂ = 0.1151. In 1, Co(II) has a slightly distorted square-pyramidal geometry defined by two O atoms and two N atoms from two glycine ligands, and by one O atom from an aqua ligand in the apical position. The molecules form a three-dimensional supramolecular network through O–H ··· O and N–H ··· O hydrogen bonds. Magnetic characterization shows 1 exhibits a negative Curie–Weiss constant and dominant spin-orbit coupling for Co(II).     

Oxalate-bridged mixed-valence trinuclear manganese(II)-manganese(III)-manganese(II) complexes: synthesis and magnetism

Summary Two novel Mn^II-Mn^III-Mn^II oxalato complexes have been synthesized and characterized, namely [Mn₂Mn(ox)₃(L)₄](ClO₄) [L = 1,10-phenanthroline (phen) or 5-nitro-1,10-phenanthroline (NO₂-phen), respectively], where ox stands for the oxalate dianion. Based on i.r., elemental analyses and electronic spectra, these complexes are proposed to have extended oxalatobridged structures consisting of Mn^II and Mn^III ions, in which Mn^III and each Mn^II ion has a distorted octahedral environment. The temperature dependence of magnetic susceptibility for [Mn₂Mn(ox)₃(phen)₄] (ClO₄) was measured over the 4.1–300 K range and the observed data were successfully simulated by an equation based on the spin-Hamiltonian operator ( = -2J( _{1 2} + _{2 3})), giving the exchange integral J = -1.57cm^–1. This indicates weak antiferromagnetic spin exchange interaction between Mn^II and Mn^III ions.     

Biomimetic Decarboxylation of Carboxylic Acids with PhI(OAc)2 Catalyzed by Manganese Porphyrin [Mn(TPP)OAcl

Manganese(Ⅲ) meso-tetraphenylporphyrin acetate [Mn(TPP)OAc] served as an effective catalyst for the oxidative decarboxylation of carboxylic acids with (diacetoxyiodo)benzene [Phl(OAc)2] in CH2C12-H2O(95:5,volume ratio),The aryl substituted acetic acids are more reactive than the less electron rich linear carboxylic acids in the presence of catalyst Mn(TPP)OAc,In the former case,the formation of carbonyl products was complete within just a few minutes with ＞97% selectivities,and no further oxidation of the produced aldehydes was achieved under these catalytic conditions,This method provides a benign procedure owing to the utilization of low toxic(diacetoxyiodo)benzene,biologically relevant manganese porphyrins,and carboxylic acids.     

A novel synthesis of (Z)-2-(1-trimethylgermyl-1-alkenyl)-1,3,2-dioxaborinanes and their conversion into carboxylic acids

A novel procedure for preparing heterocyclic compounds such as (Z)-2-(1-trimethylgermyl-1-alkenyl)-1,3,2-dioxaborinanes based on 1-trimethylgermyl-1-alkynes is described. 1-Trimethylgermyl-1-alkynes easily obtainable by deprotonation of 1-alkynes with n-butyllithium followed by treatment with trimethylgermanium chloride, are readily hydroborated in n-pentane in the presence of boron trichloride in hexane at 0 °C for 3 h. The resulting supernatant clear solution was separated from boron trichloride-methyl sulfide complex. It was then reacted with 1,3-propane diol at 0 °C for 0.5 h. The resulting representative (Z)-2-(1-trimethylgermyl-1-alkenyl)-1,3,2-dioxaborinanes were isolated in good yields (65-86%) and in high stereochemical purities (>98%) as evidenced by NMR spectral data. The carbon skeletons present in these intermediates were confirmed by alkaline hydrogen peroxide oxidation to the corresponding carboxylic acids.     

Novel Mn(II)Mn(III)Mn(II) trinuclear complexes with carbohydrate bridges derived from seven-coordinate manganese(II) complexes with N-glycoside

Reactions of MnX2.nH2O with tris(N-(D-mannosyl)-2-aminoethyl)amine ((D-Man)3-tren), which was formed from D-mannose and tris(2-aminoethyl)amine (tren) in situ, afforded colorless crystals of [Mn((D-Man)3-tren)]X2 (3a, X = Cl; 3b, X = Br; 3c, X = NO3; 3d, X = 1/2SO4). The similar reaction of MnSO4.5H2O with tris(N-(L-rhamnosyl)-2-aminoethyl)amine ((L-Rha)3-tren) gave [Mn((L-Rha)3-tren)]SO4 (4d), where L-rhamnose is 6-deoxy-L-mannose. The structures of 3b and 4d were determined by X-ray crystallography to have a seven-coordinate Mn(II) center ligated by the N-glycoside ligand, (aldose)3-tren, with a C3 helical structure. Three D-mannosyl residues of 3b are arranged in a delta(ob3) configuration around the metal, leading to formation of a cage-type sugar domain in which a water molecule is trapped. In 4d, three L-rhamnosyl moieties are in a delta(lel3) configuration to form a facially opened sugar domain on which a sulfate anion is capping through hydrogen bonding. These structures demonstrated that a configurational switch around the seven-coordinate manganese(II) center occurs depending on its counteranion. Reactions of 3a, 3b, and 4d with 0.5 equiv of Mn(II) salt in the presence of triethylamine yielded reddish orange crystals formulated as [[Mn((aldose)3-tren)]2Mn(H2O)X3.nH2O (5a, aldose = D-Man, X = Cl; 5b, aldose = D-Man, X = Br; 6d, aldose = L-Rha, X = 1/2SO4). The analogous trinuclear complexes 6a (aldose = L-Rha, X = Cl), 6b (aldose = L-Rha, X = Br), and 6c (aldose = L-Rha, X = NO3) were prepared by the one-pot reaction of Mn(II) salts with (L-Rha)3-tren without isolation of the intermediate Mn(II) complexes. X-ray crystallographic studies revealed that 5a, 5b, 6c, and 6d have a linearly ordered trimanganese core, Mn(II)Mn(III)Mn(II), bridged by two carbohydrate residues with Mn-Mn separations of 3.845(2)-3.919(4) A and Mn-Mn-Mn angles of 170.7(1)-173.81(7) degrees. The terminal Mn(II) atoms are seven-coordinate with a distorted mono-face-capped octahedral geometry ligated by the (aldose)3-tren ligand through three oxygen atoms of C-2 hydroxyl groups, three N-glycosidic nitrogen atoms, and a tertiary amino group. The central Mn(III) atoms are five-coordinate ligated by four oxygen atoms of carbohydrate residues in the (aldose)3-tren ligands and one water molecule, resulting in a square-pyramidal geometry. In the bridging part, a beta-aldopyranosyl unit with a chair conformation bridges the two Mn(II)Mn(III) ions with the C-2 mu-alkoxo group and with the C-1 N-glycosidic amino and the C-3 alkoxo groups coordinating to each metal center. These structures could be very useful information in relation to xylose isomerases which promote aldose-ketose isomerization by using divalent dimetal centers such as Mn2+, Mg2+, and Co2+.