Bridging Oxalate Research Articles

Assembly of a two-dimensional oxalate-bridged heterometallic CoII3CrIII2 coordination polymer

Reaction of CoCl(2).4H(2)O with Ag(3)[Cr(ox)(3)] (3 : 2 mol/mol) in methanol gives rise to an oxalate-bridged complex [Co(MeOH)(2)](3)[Cr(ox)(3)](2).6MeOH that consists of a rare cloverleaf-like layered structure (12,3-net). Ferromagnetic coupling is operative between the adjacent metal ions through the oxalate bridges.

Synthesis and Crystal Structure of Bis-cis-(+)-2-(4-methoxyphenyl)-4-oxo-2,3,4,5-tetrahydro-1,5-benzothiazepine-3-yl-oxalate

The crystal structure of bis-cis-(+)-2-(4-methoxyphenyl)-4-oxo-2,3,4,5-tetrahydro-1,5-benzothiazepine-3-yl-oxalate was determined as being orthorhombic, space group P212121, with lattice parameters a = 9.654(6)A, b = 13.256(1)A, c = 25.841(3)A, Z = 4, V = 3307.1(6)A3 and Dcalc = 1.355 Mg m-3. The compound crystallizes with one disordered water molecule. The carbonyl groups in the oxalate bridge are trans oriented, as indicated by the torsion angle [O(20)=C(19)-C(19′)=O(20′)] -151.5(3)°. Both 1,5-benzothiazepine rings in the molecule adopt a similar type of twist boat conformation.

Synthesis, properties and crystal structure of a Zn,Nb compound with homo- and heterodinuclear oxalate-bridged units – [{Zn(bpy) 2} 2(μ-C 2O 4)][Zn(bpy) 2(μ-C 2O 4)NbO(C 2O 4) 2] 2·0.5bpy·7H 2O: The impact of weak interactions on the crystal packing

A heterometallic Zn,Nb compound of the formula [{Zn(bpy) 2} 2(μ-C 2O 4)][Zn(bpy) 2(μ-C 2O 4)NbO(C 2O 4) 2] 2·0.5bpy·7H 2O ( 1) (bpy = 2,2′-bipyridine) has been synthesized by the reaction of the tris(oxalato)oxoniobate(V) anion, [NbO(C 2O 4) 3] 3− and [Zn(bpy) 3] 2+ in an aqueous solution, and characterized by IR and UV/vis spectroscopy, elemental and thermogravimetric analyses and X-ray single crystal diffraction method. The compound crystallizes in the triclinic P 1 ¯ space group with a = 15.9060(9), b = 16.0804(9), c = 21.5892(12) Å, α = 69.504(4), β = 82.598(5), γ = 86.012(5)°, V = 5127.5(5) Å 3, and Z = 2. The molecular structure consists of three dinuclear oxalate-bridged units, one homodinuclear Zn IIZn II and two heterodinuclear Zn IINb V units, seven water molecules and half of a bipyridine molecule. Zinc atoms are in all units octahedrally surrounded by four nitrogen atoms from the bipyridine ligands and by two oxygen atoms from the bridging oxalate groups. Niobium atoms in the two mixed Zn IINb V units adopt a pentagonal bipyramidal coordination formed by six oxygen atoms from the oxalate groups and one oxo-oxygen atom. Weak interactions, primarily hydrogen bondings and π–π stacking interactions, influence greatly the supramolecular motifs recognized in the crystal packing. Thermal decomposition of the title compound resulted in the formation of the mixed-metal Zn 3Nb 2O 8 oxide phase.

Magneto-structural correlations in a new oxalato-bridged Cu(II) alternating-exchangespin-chain compound

A new oxalato-bridged copper(II) compound,Cu(ox)(pyOH)·H2O (ox = oxalate,pyOH = 3-hydroxypyridine), has been synthesized and characterized by x-ray diffraction andmagnetic susceptibility measurements. The Cu(II) ions are bridged by oxalatemolecules with two different arrangements alternating along a chain parallel to theb-axis. To the best of our knowledge, this is the first example of a metal–oxalate chain withsuch a combination of oxalate bridges. Due to the specific structural properties, themagnetic susceptibility was analysed in the framework of an alternating-exchangespin-chain. From a least-squares fit, an antiferromagnetic coupling constantJ1 = (442 ± 5) K and an alternationparameter α = 0.13 ± 0.06 werederived, which classify Cu(ox)(pyOH)·H2O as a strongly dimerized spin-chain compound. It is argued that the strength of themagnetic coupling is mainly determined by the displacement of the Cu(II) ions out of thebasal plane of the local Cu environment.

Octacyanotungstate(V)-Based Magnetic Complex Consisting of Dimeric Mn2 and Tetrameric Mn2W2

A novel zero-dimensional (0D) octacyanotungstate(V)-manganese(II) bimetallic assembly, {[MnII(bipy)2]2(ox)}.{[MnII(bipy)2W(CN)8]2}.4H2O (1) (bipy = 2,2'-bipyridine, ox = C2O42-), was synthesized in methanol solution containing oxalic acid. X-ray analysis shows 1 is crystallized in monoclinic crystal system with C2/c space group and composed of two components of a dimeric Mn2 cation and a quadrate tetrameric Mn2W2 anion. The Mn2 and Mn2W2 moieties are connected by their respective pi-pi stacking to yield the alternative 2D layers, and the 2D layers are linked by hydrogen bonding to form a 3D network. The investigation of the magnetostructural correlation reveals that cyanide and oxalate bridges mediate weak intracluster antiferromagnetic coupling between Mn and W ions and between Mn ions, respectively. Further magnetic measurements and analysis show the spin glasses and intercluster ferromagnetic interaction exist in complex 1.

A new three-dimensional neutral framework of lanthanum oxalate: [La2(C2O4)3(DMF)(H2O)3]n

In the title complex, poly[triaquabis(dimethylformamide)di-mu3-oxalato-mu2-oxalato-dilanthanum(III)], [La2(C2O4)3(C3H7NO)(H2O)3]n, both La ions are coordinated by nine O atoms, forming slightly distorted tricapped trigonal prisms. The two La ions, the terminal water O atom, and the O and N atoms of the dimethylformamide molecule reside on twofold rotation axes, giving the two La-centered coordination geometries twofold or pseudo-twofold symmetries. The two oxalate ligands, one of which rests on a center of inversion at the mid-point of the C-C bond, adopt different bridging modes, connecting with the La ions to form two types of lanthanide oxalate chains, i.e. anionic {[La(C2O4)2(DMF)(H2O)2]n-}(n) (DMF is dimethylformamide) and cationic zigzag {[La(C2O4)(H2O)]n+}n, respectively. Each zigzag cationic chain is linked to four adjacent anionic chains via the bridging oxalate anions, and each anionic chain connects with four zigzag cationic chains, constructing a three-dimensional neutral framework.

1D copper(II) and zinc(II) coordination polymers containing an unusual twisted oxalate bridge

Two new copper(II) complexes, Cu( L1)(ClO 4) 2 ( 1), {[(μ-oxalate)Cu( L1)] · 5H 2O} n ( 2), and a zinc(II) complex, {[(μ-oxalate)Zn( L2)] · 3H 2O · 0.5DMF} n ( 3) ( L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0 1.18,0 7.12]docosane), have been synthesized and characterized by X-ray crystallography. In 1, the ligand conformation is planar, and the octahedral coordination about the copper(II) ion is completed by weakly interacting ClO 4 - ions. In 2 and 3, bridging oxalate ligands coordinate to copper(II) or zinc(II) ions in an unusually twisted bis-monodentate ( trans-1,1′-bicoordination) mode. The rigidity and steric hindrance of macrocycles L1 and L2 by the introduction of two cyclohexane rings and methyl groups on a cyclam (1,4,8,11-tetraazacyclotetradecane) skeleton cause the bridging oxalate ligands to adopt such unusual geometries in 2 and 3.

Extended Tapes of Cyclic Water Hexamers in an Unusual Oxalate-Bridged One-Dimensional Copper(II) Complex

Extended tapes of cyclic water hexamers are formed in a one-dimensional copper(II) complex bridged by oxalate with a rare mono, bidentate coordination mode. The water tapes are stabilized by the hydrogen bond interactions between uncoordinated oxalate oxygen atoms and water molecules. Magnetic analysis reveals weak ferromagnetic interactions mediated by the oxalate bridge with the exchange parameter J = 0.36 cm-1.

Heterotrimetallic Oxalato-Bridged ReIV2MII Complexes (M = Mn, Co, Ni, Cu): Synthesis, Crystal Structure, and Magnetic Properties

The use of the (NBu4)2[ReIVCl4(ox)] mononuclear species as a ligand toward divalent first row transition metal ions in the presence of imidazole affords the new trinuclear compounds of formula (NBu4)2[{ReIVCl4(mu-ox)}2MII(Him)2] [NBu4+=tetra-n-butylammonium cation, ox=oxalate dianion, Him=imidazole; M=Mn (1), Co (2), Ni (3), Cu (4)] whose preparation, crystal structures, and magnetic properties are reported. 1-4 are isostructural complexes which are made up of discrete trinuclear [{ReIVCl4(mu-ox)}2MII(Him)2]2- anions and bulky NBu4+ cations. The Re and M atoms exhibit somewhat distorted octahedral surroundings which are built by four chloro and two oxalate oxygens (Re) and two imidazole nitrogen and four oxalate oxygen atoms (M), the central M atom being linked to the two peripheral Re atoms through bis-bidentate oxalate. The values of the Re...M separation across bridging oxalate vary in the range 5.646(2) (M=Ni) to 5.794(2) A (M=Mn). Magnetic susceptibility measurements on polycrystalline samples of 1-4 in the temperature range 1.9-300 K show the occurrence of significant intramolecular antiferro- (1) and ferromagnetic (2-4) interactions. The nature and magnitude of the magnetic coupling in 1-4 are qualitatively understood through orbital symmetry considerations.

μ-Oxalato-κ4 O,O′:O′′,O′′′-bis[chloro(1,10-phenanthroline-κ2 N,N′)copper(II)

In the title dimeric complex, [Cu2(C2O4)Cl2(C12H8N2)2], which lies on a crystallographic inversion center, the CuII ion is in a distorted trigonal–bipyramidal coordination geometry formed by two N atoms from a phen ligand, two O atoms from a bridging oxalate ligand and one Cl atom. In the crystal structure, pairs of molecules related by π–π stacking interactions are stacked along the c-axis direction

Synthesis of GeFe1.4 Nanoparticles Using the Transformation of Iron Trisoxalategermanium Metal Coordination Nanopolymers by Solid Phase Reduction

In this communication, we demonstrate the novel preparation of alloy metal nanoparticles using a nanometer-sized metal coordination polymer (MCNP) as a precursor. The presented method works effectively for the construction of an uncommon alloy nanoparticle such as a IV semiconductor-transition metal alloy. Iron trisoxalategermanium MCNPs stabilized by stealylamine (SA) were newly synthesized in reverse micelle technique, and Ge-ox-Fe-SA was successfully transformed into GeFe1.4 alloy metal nanoparticles by a gas phase reduction of metal sites under H2, accompanied by the removal of the bridging oxalate ligands. The prepared GeFe1.4 nanoparticles exhibited unique ferromagnetic behavior.

Synthesis, structure and magnetic properties of a new iron phosphonate-oxalate with 3D framework: [Fe(O 3PCH 3)(C 2O 4) 0.5(H 2O)

A new iron phosphonate-oxalate [Fe(O 3PCH 3)(C 2O 4) 0.5(H 2O)] ( 1), has been synthesized under hydrothermal condition. The single-crystal X-ray diffraction studies reveal that 1 consists of layers of vertex-linked FeO 6 octahedra and O 3PC tetrahedra, which are further connected by bis-chelate oxalate bridges, giving to a 3D structure with 10-membered channels. Crystal data: monoclinic, P2 1/ n (no. 14), a = 4.851(2) Å, b = 16.803(7) Å, c = 7.941(4) Å, β = 107.516(6)°, V = 617.2(5) Å 3, Z = 4, R 1 = 0.0337 and w R 2 = 0.0874 for 1251 reflections [ I > 2 σ( I)]. Mössbauer spectroscopy measurement confirms the existence of high-spin Fe(III) in 1. Magnetic studies show that 1 exhibits weak ferromagnetism with T N = 30 K due to a weak spin canting.

One-dimensional macrocyclic zinc(II) coordination polymer containing an unusual bis-monodentate oxalate bridge

A new zinc(II) complex, {[Zn( L1)(oxalate)] · 3.5H 2O} n ( 1) ( L = 5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0 1,18.0 7, 12]docosane) has been prepared and characterized by single crystal X-ray structure determination. In 1 the rigidity and steric hindrance of the macrocycle L1 causes the bridging oxalate ligand to coordinate to the zinc(II) ions in an unusual twisted bis-monodentate coordination (1,1′-bicoordination) mode.

Lanthanide-Oxalate Coordination Polymers Formed by Reductive Coupling of Carbon Dioxide to Oxalate: [Ln2(3,5-pdc)2(C2O4)(H2O)4]？2H2O (Ln = Eu, Sm, Ho, Dy; pdc = Pyridinedicarbox

Hydrothermal reactions of <TEX>$Ln(NO_3)_3{\cdot}5H_2O $</TEX> (Ln = Eu (1), Sm (2), Ho (3), Dy (4)) with 3,5-pyridinedicarboxylic acid (3,5-pdcH2) in the presence of 4,4'-bipyridine led to the formation of the 3-D Ln(III)-coordination polymers with a formula unit of <TEX>$[Ln_2(3,5-pdc)_2(C_2O_4)(H_2O)_4]{\cdot}2H_2O$</TEX>. These polymers contain a bridging oxalate ligand (<TEX>$C_2O_4\;^2$</TEX>). On the basis of GCMS study of the mother liquor remaining after the reaction, we proposed that the <TEX>$C_2O_4\;^2$</TEX> formation proceeds in three steps: (1) Ln(III)-mediated decarboxylation of <TEX>$3,5-pdcH_2$</TEX> to give <TEX>$CO_2$</TEX>, (2) the reduction of <TEX>$CO_2$</TEX> to <TEX>$CO_2\;^{\cdot}$</TEX> by the Ln(II) species, and (3) the reductive coupling of the two <TEX>$CO_2\;^{\cdot}$</TEX> radicals to the oxalate (<TEX>$C_2O_4\;^2$</TEX>) ion. All polymers were structurally characterized by X-ray diffraction.

Structure, Magnetic and Ion-Exchange Properties of Self-Assembled Triaza-Copper(II)-Oxalate Hybrides Having Nanoscale One-Dimensional Channel

The X-ray structure, porous and magnetic property of a self-assembled network 1 is described in detail. The single crystal X-ray analysis provides 1 as a three-dimensional network, which contains two-dimensional permanent ring forming nanoscale one-dimensional channels. The inter-replacement of perchlorate and hexafluorophosphate anions in solid 1 proves its porous structure. There is somewhat strong antiferromagnetic interaction (J = -74.1 cm(-1)) between two copper(II) ions through oxalate bridge and weak antiferromagnetic interaction (J = -5.1 cm(-1) through AEP ligand.

Synthesis, crystal structure and magnetic properties of an oxalate-bridged diiron(III) complex {[Fe III(salapn)] 2(C 2O 4)}

The oxalate-bridged Schiff-based complex {[Fe III(salapn)] 2(C 2O 4)} ( 1) has been synthesized and characterized structurally (salapn = N, N′-bis(salicylaldehyde)-1,3-diaminopentane dianion). Each iron(III) ion is coordinated in slightly distorted octahedral geometry by two oxygen atoms and two nitrogen atoms from a salapn ligand, and two carboxylate oxygen atoms from an oxalate ligand. The [Fe(salapn)] moiety is linked by a bridging oxalate ligand to form a dimeric entity. The magnetic susceptibility study of 1 demonstrates the presence of antiferromagnetic interaction between two Fe(III) ions.

Structure, stacking interactions and magnetism of compounds with oxalate-bridged dinuclear Cu IICu II and Cu IINb V units

Two novel compounds of the formulae [{Cu(phen) 2} 2(μ-C 2O 4)][Cu(phen) 2(μ-C 2O 4)NbO(C 2O 4) 2] 2 · 8H 2O ( 1) and [{Cu(bpy) 2} 2(μ-C 2O 4)][Cu(bpy) 2(μ-C 2O 4)NbO(C 2O 4) 2] 2 · 0.5bpy · 7H 2O ( 2) (phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine) have been prepared and characterized by single crystal X-ray diffraction, IR spectroscopy and magnetic susceptibility measurements. The molecular structure of both 1 and 2 consists of a discrete Cu IICu II oxalate-bridged dinuclear [{Cu(L) 2} 2(μ-C 2O 4)] 2+ cation ( A unit) and two Cu IINb V oxalate-bridged dinuclear [Cu(L) 2(μ-C 2O 4)NbO(C 2O 4) 2] − anions ( B units) (L = phen, bpy). In 1 a crystallographic inversion centre is located in the middle of the oxalate bridge of the A unit, whereas in 2 an analogous inversion centre is missing. In the A units the copper(II) atoms adopt a tetragonally elongated octahedral coordination with the equatorial planes being perpendicular to the mean planes of the oxalate bridge and parallel to each other. In both structures, similar one-dimensional motifs are generated through the ligand stacking interactions, with a difference that one free bipyridine molecule, present in 2, intercalates into one of the motifs. It is shown that the phenanthroline ligand, due to its ability of stacking through the central aromatic ring, causes longer intermolecular Cu⋯Cu distances than the bipyridine ligand. The magnetic susceptibility measurements (1.8–290 K) show the ferromagnetic exchange interaction between the copper(II) atoms in the A units of both compounds, with J = +5.9 cm −1 and +7.9 cm −1 for 1 and 2, respectively ( J – the exchange parameter in the isotropic spin Hamiltonian H INT = − J S 1 · S 2).

New Heterometallic (CuII and CrIII) Complexes – First Crystal Structure of an Oxalate‐Bridged Ferromagnetically Coupled [CuIICrIIICuII] System

AbstractTwo new heterotemetallic complexes [{Cu(μ‐C2O4)(bpy)2}2Cr(C2O4)]NO3·H2O (1) and [Cu(bpy)3]2[Cr(C2O4)3]NO3·9H2O (2) (bpy = 2,2′‐bipyridine) have been synthesized. The crystal structures were determined and magnetic and spectroscopic (IR, UV/Vis) characterization accomplished. In 1, the central [Cr(C2O4)3]3– unit acts as a bridge between two copper(II) ions, each of them having a distorted octahedral geometry. The apical positions are occupied by one oxygen atom belonging to the bridging oxalate anion [Cu–O2 = 2.6439(18) Å] and one nitrogen atom from one of the bpy ligands [Cu–N1 = 2.1079(18) Å]. The N3O equatorial environment consists of three bpy nitrogen atoms [Cu–N = 1.995 Å (mean value)] and the second oxygen atom from the bridging oxalate anion [Cu–O1 = 2.1168(15) Å]. The chromium(III) atom is in a slightly distorted octahedral environment of four oxygen atoms from two bridging oxalate groups [Cr–O = 1.988 Å (mean value)] and two oxygen atoms from the terminally bonded bidentate oxalate group [Cr–O = 1.9454(16) Å]. Complex 2 consists of two mononuclear [Cu(bpy)3]2+ cations, one mononuclear [Cr(C2O4)3]3– anion, one NO3– anion and nine molecules of water of crystallisation. The copper(II) ions in two crystallographically independent [Cu(bpy)3]2+ cations are in a tetragonally distorted octahedral coordination environment of six N atoms from the bpy ligands. The chromium(III) ion in [Cr(C2O4)3]3– has a slightly distorted octahedral environment of oxygen atoms from three oxalate groups [with the Cr–O bond lengths ranging from 1.964(3) to 1.982(3) Å]. Analysis of the magnetic properties (1.8–290 K) of 1 showed a ferromagnetic exchange interactionbetween CuII and CrIII with J = +1.20 cm–1 [using HINT =–J(SCu1SCr + SCu2SCr)].(© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2006)

Heterometallic Cr−Mn Complexes Containing Cyanide and Oxalate Bridges

Three heterometallic Cr-Mn compounds, {Mn(mu-ox)0.5(H2O) [Cr(phen)(CN)4]}n.n H2O.2n CH3OH, (1), {Mn(mu-ox)0.5(H2O)[Cr(bpy)(CN)4]}n.2n H2O x n CH3OH, (2), and {Mn(mu-ox)0.5(bpy)[Cr(bpy)(CN)4]}n, (3) (ox = oxalate), containing cyanide and oxalate bridges based on building blocks [Cr(L)(CN)4]- (L = phen and 2,2'-bipyridine) have been prepared. A new approach was first employed to synthesize ox-bridged compounds via facile oxidation-hydrolysis reactions of diaminomaleonitrile. X-ray crystallography revealed that the structures of 1 and 2 are similar, where cyano-bridged corrugated ladderlike chains are further connected through bis-bidentate oxalato bridges to unique two-dimensional layered structures. Of note is that the introduction of 2,2'-bipyridine led to an interesting cluster-based chainlike compound (3) with cyano-bridged squares [Mn2Cr2] extended by ox bridges. Magnetic studies show antiferromagnetic (AF) interaction between cyano-bridged Cr(III)-Mn(II) and ox-bridged Mn(II)-Mn(II) ions, with the result that 1 and 2 exhibit AF ordering with spin-flop behaviors below 18 and 19 K, respectively.

Structure characterization of several oxalate-bridged transition-metal coordination polymers

Four oxalate-bridged transition-metal supramolecular compounds [Co 2(im) 4(ox) 2] 1, [Co(im) 2(ox)] 2, [Mn(2,2′-bpy)(ox)] 3 and [Fe(H 2O) 2(ox)] 4 (im, imidazole; ox, oxalate; bpy, bipyridine) were obtained from the simple hydrothermal reactions of M n+ ox L (M, transition metal; L, aromatic N-donor ligand) system. They all exhibit the 1-D chain structures, consisting of the ML 2 2 + (or ML 2+) units linked by oxalate bridges. Interestingly, the 1-D oxalate chains in the title compounds are further self-assembled into the 3-D supramolecular networks through the interchain various secondary bonding interactions. Because the ML 2 2 + units adopt the different configuration, the oxalate chains show either zigzag type as in compounds 1– 3 or linear type as in compound 4. Compounds 1 and 2 are isomeric, and only in packing modes of interchain im molecules there exists the difference.