Bridging Methoxo Research Articles

Catalytic oxidation of styrene by dinuclear Mn(III) coordination compound with asymmetric tridentate half-Salen type NNO-donor ligand

A new methoxo bridged dinuclear Mn(III) coordination compound, [Mn2(µ-OMe)2(L)2(MeOH)2]Cl2∙2MeOH (1), with tridentate N2O-donor half-Salen ligand was synthesized by the reaction of MnCl2·4H2O and (Z)-3-((2-aminocyclohexyl)amino)-1-phenylbut-2-en-1-one (HL) in methanol and characterized by spectroscopic methods and elemental analysis. The structure of compound 1 was also determined by single crystal X-ray diffraction studies which indicated it is a dinuclear Mn(III) coordination compound. Two Mn(III) are connected together by two methoxo bridges and have distorted octahedral geometry. The coordination compound is ionic and two chloride anions appear as the counter anions which are involved in strong hydrogen bond interactions. The catalytic activity of compound 1 was investigated in oxidation of styrene in the presence of hydrogen peroxide as a green oxidant. The effects of influencing parameters like molar ratio of the reagents, temperature and the presence of different solvents were investigated. The results of catalytic studies indicated the selectivity and activity of this catalytic system considerably depend on the reaction condition. Temperature and molar ratio of oxidant to substrate have high influence on both conversion and selectivity of the oxidation products. The best selectivity toward styrene epoxide was obtained at 40 °C and the best TOF was 66.4 h−1. The results indicate half-salen Mn(III) coordination compound can act as selective and efficient catalyst for oxidation of styrene under mild condition

New Dinuclear Methoxo-Bridged Manganese(III) complex: Synthesis, Characterization and Usage as New Precursor for Synthesis of Mn2O3 Particles

New dinuclear methoxo-bridged manganese(III) complex [Mn2((MeO-bph)en)2Cl2(m-CH3O)2] (1) was synthesized by template reaction of 2-hydroxy-4-methoxybenzophenone, 1,2-ethanediamine and MnCl2×6H2O with molar ration (1:1:1) in methanol as solvent. The title compound 1 was characterized by elemental analyses (CHN), Fourier Transform infrared spectroscopy (FT-IR) and single crystal X-ray diffraction. X-ray result reveal that 1 is dimeric with methoxo bridges between two symmetry equivalent manganese ions. The Mn ions are surrounded in a distorted octahedral geometry influenced by Jahn-Teller effect. The tridentate Schiff base ligand MeO-bp-en and one of the methoxo-bridges bind in the equatorial mode, whereas in the axial positions, other metoxo-bridge and Cl atom bind to the Mn ions. Thermogravimetric analysis of 1 was studied and display the title compound 1 decompose in three stages. Finally, by calcination of 1 at 500 °C for 3 h, we prepared Mn2O3 particles and characterized by FT-IR, XRD and SEM.

Structural Characterization of Iron(iii) Dinuclear Complexes

Dinuclear complexes have been studied for different purposes: magnetic materials[1], Non-linear optics materials[2], molecular switches [3], mixed-valence systems, etc. With these antecedents in mind, we present in this work a new series of dinuclear Iron(III) complexes formed by different Schiff bases ligands. The reaction starting from the iron chloride salts with the 5-chloro or 5-bromo-salycilaldehyde and ethylendiamine yields two different kinds of dinuclear iron complexes in different reaction conditions. The first one (Fig N°1), are methoxo-bridged dinuclear iron(III) complexes in which each metal centre is coordinated with one mono-condensated Schiff base ligand, one 4-chloro or 4-bromo-2-(dimethoxymethyl)phenoxo ligand and two bridging methoxo ligands. The iron(III) centres are hexacoordinated (FeN2O4), the coordination sphere is formed by 2 nitrogen atoms of the ethylendiamine fragment, 2 oxygen atoms from the hydroxyl of the Schiff base and two O atoms from the methoxo ligands. Both iron(III) centres are related by a inversion centre. The second one (Fig N°2), the dinuclear complex is formed for the double condensation of ethylendiamine with 5-chloro or 5-bromo-salycilaldehyde and one oxygen from the dianionic ligand act as bridge with another unit. The iron (III) centres are also hexaccordinated (FeN2O3Cl) formed by 2 nitrogen atoms from ethylendiamine fragment and 3 oxygen atoms from hydroxyl from Schiff base ligands and one chloro ligand. Finally, the electronic and redox properties have been studied by UV-Visible and cyclic voltammetry. ACKNOWLEDGMENT FONDECYT N01130640, FONDEQUIP EQM120095 and Beca CONICYT folio 21130944

Two C3 -symmetric Dy3III complexes with triple di-μ-methoxo-μ-phenoxo bridges, magnetic ground state, and single-molecule magnetic behavior.

Two series of isostructural C(3)-symmetric Ln(3) complexes Ln(3)⋅[BPh(4)] and Ln(3)⋅0.33[Ln(NO(3))(6)] (in which Ln(III) =Gd and Dy) have been prepared from an amino-bis(phenol) ligand. X-ray studies reveal that Ln(III) ions are connected by one μ(2)-phenoxo and two μ(3)-methoxo bridges, thus leading to a hexagonal bipyramidal Ln(3)O(5) bridging core in which Ln(III) ions exhibit a biaugmented trigonal-prismatic geometry. Magnetic susceptibility studies and ab initio complete active space self-consistent field (CASSCF) calculations indicate that the magnetic coupling between the Dy(III) ions, which possess a high axial anisotropy in the ground state, is very weakly antiferromagnetic and mainly dipolar in nature. To reduce the electronic repulsion from the coordinating oxygen atom with the shortest Dy-O distance, the local magnetic moments are oriented almost perpendicular to the Dy(3) plane, thus leading to a paramagnetic ground state. CASSCF plus restricted active space state interaction (RASSI) calculations also show that the ground and first excited state of the Dy(III) ions are separated by approximately 150 and 177 cm(-1), for Dy(3)⋅[BPh(4)] and Dy(3)⋅0.33[Dy(NO(3))(6)], respectively. As expected for these large energy gaps, Dy(3)⋅[BPh(4)] and Dy(3)⋅0.33[Dy(NO(3)(6)] exhibit, under zero direct-current (dc) field, thermally activated slow relaxation of the magnetization, which overlap with a quantum tunneling relaxation process. Under an applied Hdc field of 1000 Oe, Dy(3)⋅[BPh(4)] exhibits two thermally activated processes with U(eff) values of 34.7 and 19.5 cm(-1), whereas Dy(3)⋅0.33[Dy(NO(3))(6)] shows only one activated process with Ueff =19.5 cm(-1).

A binuclear Cu(II) complex of a Schiff-base type polyhydroxyl ligand with asymmetrical phenoxo and methoxo bridges: crystal structure and magnetic properties

[Cu2(H4L)(OCH3)(H2O)] · 2MeOH (1) has been synthesized from the reaction of 2-hydroxy-5-methylisophthalaldehyde, tris(hydroxymethyl)aminomethane and copper(II) perchlorate in methanol with the Schiff-base polyhydroxyl ligand (H4L)3− formed in situ. Single-crystal X-ray structure analysis of 1 reveals a binuclear structure with Cu(II) asymmetrically bridged by a methoxo and a phenoxo group with Cu–O–Cu bridging angles of 102.93(7)° and 100.17(7)°, respectively. The binuclear Cu(II) moieties utilize the coordinated and noncoordinated alkoxyl groups for formation of intermolecular hydrogen bonds, thus affording a 3-D supramolecular structure. Variable temperature magnetic measurements reveal strong antiferromagnetic coupling in 1 with the 2J-value of −729 cm−1, which was mediated cooperatively by the methoxo and phenoxo bridges. Magneto-structural correlations are discussed based on the crystal structure.

Modeling the Geometric, Electronic, and Redox Properties of Iron(III)-Containing Amphiphiles with Asymmetric [NN′O] Headgroups

Two iron(III)-containing amphiphiles 1 and 2 have been synthesized with the [NN'O] ligands HL(tBu-ODA) (2-((octadecyl(pyridin-2-ylmethyl)amino)methyl)-4,6-di-tert-butylphenol) and HL(I-ODA) (2-((octadecyl(pyridin-2-ylmethyl)amino)methyl)-4,6-diiodophenol), respectively. Compound 1 is monometallic, whereas EXAFS data suggest that 2 is a mixture of mono- and bimetallic species. The archetypical [Fe(III)(L(NN'O))(2)](+) complexes 3-9 have been isolated and characterized in order to understand the geometric, electronic, and redox properties of the amphiphiles. Preference for a monometallic or bimetallic nuclearity is dependent on (i) the nature of the solvent used for synthesis and (ii) the type of the substituent in the phenol moiety. In methanol, the tert-butyl-, methoxy-, and chloro-substituted 3, 4, and 5 are monometallic species, whereas the bromo- and iodo-substituted 6 and 7 form bimetallic complexes taking advantage of stabilizing methoxo bridges generated by solvent deprotonation. In dichloromethane, the bromo- and iodo-substituted 8 and 9 are monometallic species; however, these species favor meridional coordination in opposition to the facial coordination observed for the tert-butyl- and methoxy-substituted compounds. Molecular structures for species 5, 7, 8, and 9 have been solved by X-ray diffraction. Furthermore, the electronic spectrum of the amphiphile 1 was expected to be similar to those of facial/cis archetypes with similar substituents, but close resemblance was observed with the profile for those meridional/cis species, suggesting a similar coordination mode. This trend is discussed based on DFT calculations, where preference for the meridional/cis coordination mode appears related to the presence of tertiary amine nitrogen on the ligand, as when a long alkyl chain is attached to the [NN'O] headgroup.

Isolation of four new CoII/CoIII and NiII complexes with a pentadentate Schiff base ligand: syntheses, structural descriptions and magnetic studies

In this paper we report the temperature and pH dependent syntheses and systematic characterization of four new Co(II)/Co(III) and Ni(II) complexes with a pentadentate Schiff base ligand H(3)L obtained by condensing 1,3,-diaminopropan-2-ol with 2-hydroxyacetophenone in 1:2 molar ratio. The room temperature syntheses involving Co(II) and Ni(II) nitrates and the ligand H(3)L lead to the isolation of the dinuclear species [Co(2)L(2)(H(2)O)] (1), and the mononuclear complex [Ni(LH)] (3), respectively, whereas refluxing at basic pH leads to the tetranuclear complexes, [Co(II)(2)Co(III)(2)L(2)(μ(3)-OMe)(2)(NO(3))(H(2)O)(2)]NO(3)·2(H(2)O) (2), and [Ni(4)L(2)(μ(3)-OMe)(2)(H(2)O)(2)]·2H(2)O (4). 1 is found to be a simple mono alkoxo-bridged Co(III) dinuclear species, whereas 2 and 4 are both rhomb-like tetrameric complexes with double oxo bridges and μ(3)-methoxo bridges, derived from the methanol solvent, in an open dicubane arrangement. Moreover 2 shows six coordinate ordered Co(II) and Co(III) ions and 4 has both six- and five-coordinate Ni(II) centers. Compound 3 is assigned a tentative mononuclear structure based on IR, UV-Vis spectroscopic, (1)H-NMR and ESI mass study results and is supposed to have one Ni(II) center coordinated with a ligand fragment in square planar geometry. The variable temperature magnetic susceptibility study for 2 and 4 is performed which indicate for both 2 and 4 the presence of intracluster dominant ferromagnetic interactions.

Synthesis, Crystal structure, and Magnetic Properties of Dinuclear Iron(III) Complexes with Methoxo Bridges

The reaction of stoichiometric amount of <TEX>$FeCl_2{\cdot}4H_2O$</TEX>, (2-pyridylmethyl, 3-pyridylmethyl)amine (2,3-pyma) and sodium azide/sodium thiocyanate in methanol under aerobic conditions affords the dinuclear Fe(III) complexes, [(2,3-pyma) <TEX>$(N_3)_2Fe({\mu}-OCH_3)_2Fe(N_3)_2$</TEX>(2,3-pyma)]<TEX>${\cdot}CH_3OH$</TEX> (1) and [(2,3-pyma)<TEX>$(NCS)_2Fe({\mu}-OCH_3)_2Fe(NCS)_2$</TEX>(2,3-pyma)] (2) in good yield. Two bis-methoxy-bridged diiron(III) complexes are isolated and characterized. The coordination geometries around iron(III) ions in 1 and 2 are the same tetragonally distorted octahedron. The iron(III) ions are coordinated by two nitrogens of a 2,3-pyma, two nitrogens of two azide/thiocyanate ions, and two oxygens of two methoxy groups. Both compounds are isomorphous. The structures of 1 and 2 display the C-<TEX>$H{\cdots}\pi$</TEX> and/or <TEX>$\pi-\pi$</TEX> stacking interactions as well as hydrogen bonding interactions, respectively. Compounds 1 and 2 show significant antiferromagnetic couplings through the bridged methoxy groups between the iron(III) ions in the temperature range from 5 to 300 K (<TEX>$H=-2JS_1{\cdot}S_2$</TEX>, J=-19.1 and <TEX>$-13.9\;cm^{-1}$</TEX> for 1 and 2).

Spin Exchange Coupling in Dimethoxo-Bridged Dichromium(III) Complexes: A Density Functional Theory Study

For the [Cr2(H2tmp)2Cl4] compound, simplified models with two bridging methoxo ligands have been studied. The influence of the bridging Cr-O-Cr bond angles on the exchange coupling between metal atoms in the model compound has been analyzed by means of density functional calculations with the broken-symmetry approach. Coupling constant calculated for the full structure is in good agreement with the experimentally reported value, confirming the validity of the computational strategy used in this work to predict the exchange coupling in a family of related dinuclear Cr(III) compounds. The calculations indicate a good correlation between the calculated coupling constant and the sum of the squared energy gap of three pairs of metal t2g OMSOs with a limited variation of the Cr-O-Cr angle. The spin density distribution and the mechanism of magnetic coupling interactions are discussed.

Two new alkoxo-bridged dinuclear copper(II) complexes with 3-aminopyrazidine-2-carboxylic acid as ligands

The synthesis, spectroscopic and magnetic properties of two new alkoxo-bridged dinuclear copper(II) complexes are described. Both compounds have the general formula [Cu(μ-OR)(L)2]2X2 · H2O, in which μ-OR = CH3O− or C2H5O−, L = 3-aminopyrazidine-2-carboxylic acid and X = . The title complexes consist of a dinuclear unit with bridging methoxo for [Cu(μ-OCH3)(L)2]2(NO3)2 · H2O (1) and bridging ethoxo for [Cu(μ-OC2H5)(L)2]2(NO3)2 · H2O (2) with two ligands linked to each copper via pyrazidine N atom, providing a square pyramidal CuN2O2 unit. Both compounds have been synthesized in a one-step reaction and characterized by elemental analysis, FTIR, ESR, electronic spectra and by room temperature magnetic moments. The compounds exhibit antiferromagnetic interaction at room temperature. The UV-vis spectra show three absorption bands, attributed to d–d transitions of copper, ligand → metal charge transfer and π → π*; or n → π*; transitions of ligand. The FTIR spectra indicate Cu2O2 ring vibration in 570–450 cm−1 range. Both complexes show a room temperature magnetic moment of about 1.50 B.M. per copper atom. The X-band electron spin resonance (ESR) studies indicate a weak half-field band, characteristic of the Cu(II)–Cu(II) dimer, observed at about 1600 gauss. The observation of this band strongly suggests that the hyperfine structure arises from a spin triplet species. The spectrum of frozen samples in DMF or in DMSO at liquid nitrogen temperature shows a typical Δm = 1 transition.

Synthesis and Reactivity of the Methoxozirconium Pentatungstate (nBu4N)6[{(μ-MeO)ZrW5O18}2]: Insights into Proton-Transfer Reactions, Solution Dynamics, and Assembly of {ZrW5O18}2- Building Blocks

The methoxo-bridged, dimeric, ZrIV-substituted Lindqvist-type polyoxometalate (POM) (nBu4N)6[{(mu-MeO)ZrW5O18}2], (TBA)61, has been synthesized by stoichiometric hydrolysis of Zr(OnPr)4, [{Zr(OiPr)3(mu-OnPr)(iPrOH)}2], or [{Zr(OiPr)4(iPrOH)}2] and [{WO(OMe)4}2] in the presence of (nBu4N)2WO4, providing access to the systematic nonaqueous chemistry of ZrW5 POMs for the first time and an efficient route to 17O-enriched samples for 17O NMR studies. 1H NMR provided no evidence for dissociation of 1 in solution, although exchange with MeOH was shown to be slow by an EXSY study. Reactions with HX at elevated temperatures gave a range of anions [{XZrW5O18}n]3n- (X = OH, 3; OPh, 4; OC6H4Me-4, 5; OC6H4(CHO)-2, 6; acac, 7; OAc, 8), where n = 2 for 3 and n = 1 for 4-8, while 1H and 17O NMR studies of hydrolysis of 1 revealed the formation of an intermediate [(mu-MeO)(mu-HO)(ZrW5O18)2]6-. Electrospray ionization mass spectrometry of 1 and 3 illustrated the robust nature of the ZrW5O18 framework, and X-ray crystal structure determinations showed that steric interactions between ligands X and the ZrW5O18 surface are important. The coordination number of Zr is restricted to six in aryloxides 4 and 5, while seven-coordination is achieved in the chelate complexes 6-8. Given the inert nature of the methoxo bridges in 1, protonation of ZrOW sites is proposed as a possible step in reactions with HX. The diphenylphosphinate ligand in [(Ph2PO2)ZrW5O18]3- was found to be labile and upon attempted recrystallization the aggregate [(mu3-HO)2(ZrW5O18)3H]7- 9 was formed, which was found to be protonated at ZrOZr and ZrOW sites. This work demonstrates the flexibility of the {ZrW5O18}2- core as a molecular platform for modeling catalysis by tungstated zirconia surfaces.

Synthesis and Single Crystal Structure of a New Dinuclear Copper(II) Complex of 1,5-Bis(8-oxaquinoline)-3-methylpentane

A new flexible ligand, 1,5-bis(8-oxaquinoline)-3-methylpentane (C5MeOQ), was synthesized and used in the preparation of the new dinuclear copper(II) complex 1: [Cu2(μ-OMe)2(μ-C5MeOQ)(NO3)2]. Single crystal X-ray analysis revealed that complex 1 contains dinuclear Cu(II) units with bridging methoxo groups. The ligand, C5MeOQ, takes on a bent conformation in order to connect to and complete the square planar coordination environment of both copper centers; and one of the two Cu(II) centers adopts a distorted square planar configuration as a result of the ligand conformation. The magnetic properties of complex 1 were investigated by variable-temperature magnetic susceptibility measurements in the 100–300 K range. Interestingly, the susceptibility data for complex 1 reveals that the compound is diamagnetic, suggesting the presence of very strong antiferromagnetic coupling interactions between the adjacent Cu(II) centers.

α,β-Unsaturated Carbonyl Compounds as Hard/Soft Chelating Ligands in Methyl Nickel Phenolates and the Structure of trans-Methyl-2-(3-phenyl-2,3-η2- propenoyl)phenolatobis(trimethylphosphine)nickel(II)

Phenolato functions of chalcone type compounds may replace both methoxo bridges in dinuclear methyl nickel complexes without utilizing the aldehyde functions. Cleavage of phenolato-bridged nickel(II) centers in square planar coordination geometry by addition of trimethylphosphine affords mononuclear methylnickel complexes of coordination number five. The trimethylphosphine-supported trigonal bipyramidal methyl nickel(II) complex has a hard/soft chelating ligand with a phenolato oxygen atom and a π-coordinated olefin functional group. The chemical reactivity of complexes with these novel hard/soft chelating ligands remains to be clarified.

Binuclear copper(II) oxidation products from copper(I) complexes with tridentate ligands. Magnetostructural characterization.

The bis-pyridine tridentate ligands (6-R-2-pyridylmethyl)-(2-pyridylmethyl) benzylamine (RDPMA, where R = CH(3), CF(3)), (6-R-2-pyridylmethyl)-(2-pyridylethyl) benzylamine (RPMPEA, where R = CH(3), CF(3)), and the bidentate ligand di-benzyl-(6-methyl-2-pyridylmethyl)amine (BiBzMePMA) have been synthesized and their copper(I) complexes oxidized in a methanol solution to afford self-assembled bis-micro-methoxo-binuclear copper(II) complexes (1, 2, 4, 6) or hydroxo- binuclear copper(II) complexes (3). Oxidation of the nonsubstituted DPMA (R = H) in dichloromethane gives a chloride-bridged complex (5). The crystal structures for [Cu(MeDPMA)(MeO)](2)(ClO(4))(2) (1), [Cu(RPMPEA)(MeO)](2)(ClO(4))(2) (for 2, R= Me, and for 4, R = CF(3)), [Cu(BiBzMePMA)(MeO)](2)(ClO(4))(2) (6), [Cu(FDPMA)(OH)](2)(ClO(4))(2) (3), and [Cu(DPMA)(Cl)](2)(ClO(4))(2) (5) have been determined, and their variable-temperature magnetic susceptibility has been measured in the temperature range of 10-300 K. The copper coordination geometries are best described as square pyramidal, except for 6, which is square planar, because of the lack of one pyridine ring in the bidentate ligand. In 1-4 and 6, the basal plane is formed by two pyridine N atoms and two O atoms from the bridging methoxo or hydroxo groups, whereas in 5, the bridging Cl atoms occupy axial-equatorial sites. Magnetic susceptibility measurements show that the Cu atoms are strongly coupled antiferromagnetically in the bis-methoxo complexes 1, 2, 4, and 6, with -2J > 600 cm(-)(1), whereas for the hydroxo complex 3, -2J = 195 cm(-)(1) and the chloride-bridged complex 5 shows a weak ferromagnetic coupling, with 2J = 21 cm(-)(1) (2J is an indicator of the magnetic interaction between the Cu centers).

Di-μ-methoxo-bis[dipyridinecopper(II)] diperchlorate

The title compound, [Cu2(CH3O)2(C5H5N)4](ClO4)2, consists of a centrosymmetric dinuclear unit with bridging methoxo groups, and each CuII atom forms a square-planar CuN2O2 unit with pyridine ligands. The Cu⋯Cu distance is 2.9336 (11) A and the Cu—O—Cu bond angle is 99.51 (7)°. The perchlorate anions are at semi-coordination distances, the Cu—O(perchlorate) distances being in the range 2.649 (2)–2.741 (2) A.

Synthesis, spectroscopy, crystal structure and magnetism of tetrakis(2-aminopyrimidine)bis(μ-methoxo)bis(perchlorato)dicopper(II): a rare case of distortion isomerism

The dinuclear compound [Cu(ampym) 2(μ-CH 3O)(ClO 4)] 2 (ampym=2-aminopyrimidine) has been synthesized and characterized by X-ray crystallography and infrared spectroscopy. In addition, EPR and magnetic measurements have been performed and related to the dinuclear structural details. The compound crystallizes in the monoclinic space group P2 1/ c, with a=8.0190(13), b=18.2500(11), c=10.955(2) Å, β=116.390(13)°, V=1436.2(4) Å 3 and Z=2. The coordination geometry around the Cu(II) ion is distorted square pyrimidal with the basal plane formed by two nitrogen atoms of two ampym molecules (Cu–N distances 2.002(3) and 2.031(3) Å) and two oxygen atoms of the bridging methoxo molecules (Cu–O distances of 1.936(2) and 1.937(3) Å). The apical position is occupied by a semi-coordinated oxygen of a perchlorate anion (Cu–O distance 2.442(2) Å). The H-bonds, formed by the amino group and the uncoordinated pyrimidine nitrogen atom of a neighbouring ampym molecule, give rise to an interesting Watson–Crick type pairwise aggregation of ampym ligands. In the far-IR, the Cu–N vibrations are observed at 443 and 265 cm −1, and the Cu–O are observed at 353 and 240 cm −1. At room temperature the compound gives an EPR silent behaviour and magnetic susceptibility measurements, down to 4 K, agree with a strong antiferromagnetic interaction having a very large singlet–triplet splitting ( J=−621 cm −1). The title compound appears to be a distortion isomer of a recently reported X-ray structure of identical stoichiometry.

The [Cu 2(O 2CMe) 4(btd) 2] complex as a bridging unit: preparation, characterisation, X-ray structure and magnetism of the 2D coordination polymer {[Cu 6(O 2CMe) 8(OMe) 4(btd) 2]} n (btd=2,1,3-benzothiadiazole)

A systematic investigation of the [Cu 2(O 2CMe) 4(H 2O) 2]/btd reaction system is described, where btd=2,1,3-benzothiadiazole. Reaction of [Cu 2(O 2CMe) 4(H 2O) 2] with 5–8 equiv. of btd in both MeCN and MeOH yields [Cu 2(O 2CMe) 4(btd) 2] ( 1) in 40–50% yields. Treatment of [Cu 2(O 2CMe) 4(H 2O) 2] with 1.4 or 0.7 equiv. of btd in MeOH leads to the precipitation of the polymeric compound {[Cu 6(O 2CMe) 8(OMe) 4(btd) 2]} ( 2) in 82% yield. Reaction of 1 with two equivalents of [Cu 2(O 2CMe) 4(H 2O) 2] in MeOH under reflux provides an additional route to 2. The structure of 1 consists of centrosymmetric dinuclear [Cu 2(O 2CMe) 4(btd) 2] molecules of the paddle-wheel cage type. The two Cu II ions are bridged by four η 1:η 1:μ 2 acetates, while a monodentate btd is at the apex of the square pyramid of each metal centre. The 2D structure of 2 consists of chains of tetranuclear, planar Cu 4(OMe) 4(O 2CMe) 4 repeating units running along the a axis, which are connected along the cell body diagonal via Cu 2(O 2CMe) 4(btd) 2 paddle-wheel dinuclear units. The btd molecules behave as bidentate bridging ligands. Within the tetranuclear units, each Cu II ion is connected via two acetate bridges with one neighbouring Cu II ion and via two methoxo bridges with the other neighbouring Cu II ion; intertetranuclear linking is provided by two monoatomic acetate bridges. The results of solid state magnetic susceptibility studies are described for complex 2 in the temperature range 3–300 K. The results reveal antiferromagnetic exchange interactions between the Cu II ions. The complicated structure of 2 does not permit an exact treatment for the determination of the various exchange interactions. However, an approximate 3- J magnetic model was constructed, resulting in an excellent fit. An orbital interpretation of the J-trend derived is also attempted.

X-ray crystal structures, spectroscopic and magnetic measurements of dinuclear alkoxo-bridged copper(II) compounds with substituted bis(2-benzimidazolyl)alkane ligands. First X-ray structure of a copper(II) dinuclear propoxo-bridged compound

The synthesis and characterization of three new alkoxo-bridged dinuclear copper(II) compounds are described, all having the general formula [Cu 2(L) 2(RO −) 2](ClO 4) 2(ROH) y (H 2O) z , in which L=b2b (bis(2-benzimidazolyl)-2-butane) and b3b (bis(2-benzimidazolyl)-3-butane), ROH=MeOH, EtOH, 1-PrOH, y=1 or 2, z=0 or 3. The X-ray structure has been solved from two compounds; [Cu 2(b2b) 2(OCH 3) 2](ClO 4) 2(CH 3OH) 2(H 2O) 3 ( 1) and from compound [Cu 2(b3b) 2(C 3H 7O) 2](ClO 4) 2(C 3H 7OH) 2 ( 3). These two compounds consist of dinuclear Cu(II) units with bridging methoxo group for 1 and an unique bridging propoxo group for 3 with two ligands linked to each copper via N, providing square–planar CuN 2O 2 chromophores. The latter one is the first dinuclear Cu(II) X-ray structure with bridging propoxo groups. Both dinuclear compounds are diamagnetic.

Amido-tert-butylimido-vanadium(V)-Verbindungen. Darstellung, Reaktionen und 51V-NMR-spektroskopische Untersuchungen / Amido-tert-butylimidovanadium(V) Compounds. Synthesis, Reactions and 51V NMR Spectroscopic Studies

The reactions of tBuN = VCl2 · DME with LiX (X = NHtBu, NR2, OSiPh3, SR, Alkyl, Cp) have been studied. LiNHtBu and LiCH3 furnish the binuclear diamagnetic tert-butylimido-vanadium( IV) compounds [(μ-NtBu)2V2X4]; in all other cases only the vanadium(V) compounds tBuN=VX3 and tBuN=VCpCl2 formed by disproportionation reactions of vanadium(IV) can be isolated. The syntheses of various mononuclear amido tert-butylimido-vanadium(V) complexes as well as of the binuclear complexes [μ-NtBu)2V2(NtBu)2Cl2] and [(μ-0)V2(NtBu)2Cp2Cl2] are also described. All compounds obtained have been characterized by 51V NMR spectroscopy. tBuN=V(OMe)3 was investigated by X-ray diffraction analysis; the molecular structure has been found to be that of a binuclear vanadium(V) complex with two bridging methoxo ligands.

Interactions of metal ions with a 2,4-diaminopyrimidine derivative (trimethoprim): Antibacterial studies

The interaction of copper (II), zinc(II) and cadmium(II) with Trimethoprim (2,4-diamino-5-(3′,4′,5′-trimethoxybenzyl) pyrimidine) has been studied. The crystal structures of [Zn(Trim) 2Cl 2] ( 2) and [Cd(Trim)Cl 2(CH 3OH)] n ( 4) are reported. Compound ( 2) exhibits a distorted tetrahedral environment around the metal center and crystallizes in the triclinic space group P1̄ with a=10.2397(6), b=10.4500(6), c=16.3336(16) Å, α=96.141(8), β=106.085(5), γ=96.551(5)° and Z=2. In complex ( 4), the Cd(II) centers are bridged sequentially by two chlorine ions to form infinite chains and present a six-coordinated environment; the compound crystallizes in the monoclinic P2 1/ C space group with a=13.958(5), b=7.532(2), c=18.390(2) Å, α=90, β=97.32(5), γ=90° and Z=4. In both structures the Trimethoprim acts as a monodentate ligand through the pyrimidinic nitrogen N(1) atom. The characterization of the Cu(Trim) 2(CH 3O)(ClO 4) complex through EPR and magnetic measurements suggests a binuclear or polinuclear nature, with bridging methoxo groups. The complexes were screened for their activity against several bacteria, showing activity similar to that of trimethoprim.