Oxime Oxygen Research Articles

Structural studies on copper(II) complex containing (Z)-2-(2-Aminothiazol-4-yl)- N-(2-hydroxyethyl)-2-(hydroxyimino) acetamide, A model compound for a cephalosporin antibiotic cefdinir

(Z)-2-(2-aminothiazol-4-yl)-N-(2-hydroxyethyl)-2-(hydroxyimino)acetamide (HL) has been employed as a model compound for an orally active cephalosporin antibiotic, Cefdinir (CFDN). A binuclear copper(II) complex Cu 2L 4 (1) has been obtained from an aqueous solution containing CuCl 2 and HL, and its structure determined by means of X-ray crystallography: monoclinic, P2/c, a = 11.954(3) A ̊ , b = 10.661(3) A ̊ , c = 16.969(7) A ̊ , β = 108.13(3)°, Z = 2 . The molecular structure of 1 is a dimeric copper(II) complex consisting of two copper(II) complex units CuL 2, where the two molecules of L (L a and L b) are coordinated to the copper atom through their thiazole and oximate nitrogen atoms. L a is also coordinated to the copper atom of the other CuL 2 unit through the oximate oxygen atom, namely, the two complex units are bound to each other by forming a pair of oximate NO bridges of the two L a molecules. The coordination environment of the copper atom is a distorted trigonal bipyramid. In addition, based on the molecular structure, the coordination property of CFDN to copper(II) in water has been clarified by means of spectrophotometry and titration. Both copper(II) (0.05 mM)-HL (0.1 mM) and copper(II) (0.05 mM)-CFDN (0.1 mM) aqueous solutions gave broad d-d bands at ca. 720 nm above pH 6, corresponding to that observed in the diffuse reflectance spectrum of the crystals of 1. The results indicate that CFDN also forms a binuclear copper(II) complex, Cu 2(CFDN) 4, corresponding to Cu 2L 4 as the main species in water above pH 7. Stability constants are as follows: log β 110 = 11.12, log β 240 = 41.13 for copper(II)-L complexes. The theoretical species distribution diagram as a function of pH for the copper(II) (0.05 mM)-HL (0.1 mM) system shows that Cu 2L 4 exists as the main species above pH 7. The titration results are consistent with the spectral data. The spectral and titration studies indicate that not only HL, but also CFDN forms a binuclear complex Cu 2(CFDN) 4 corresponding to Cu 2L 4 as the main species under the neutral and basic conditions. In addition, the stability constants of CFDN complexes should be as large as those of CuL complexes, although titrations for copper(II)-CFDN systems could not be carried out due to precipitation of copper(II)-CFDN complexes.

Tuning the nature of the exchange interaction in out-of-plane oximato-bridged dinuclear copper(II) complexes

The dinuclear copper(II) complexes of formula [{Cu(Hdmg) 2 } 2 ] 1, [{Cu(Hbdmg)} 2 ][ClO 4 ] 2 2, [{Cu(Hdeg) 2 } 2 ] 3 and [{Cu(Hchd) 2 } 2 ] 4 (H 2 dmg, H 2 bdmg, H 2 deg and H 2 chd = dimethylglyoxime, 3,10-dimethyl-4,9-diazadodeca-3,9- diene-2,11-dione dioxime, diethylglyoxime and cyclohexane-1,2-dione dioxime) have been synthesized. The structures of 3 and 4 have been determined by single-crystal X-ray diffraction methods. Both consist of centrosymmetric dinuclear bis(alkyl)glyoximatocopper(II) entities where the units are staggered so that the copper atom of one unit is directly opposite to the oxime-oxygen atom of the other, as previously found for 1 and 2. Each metal atom in 3 and 4 is five-co-ordinate with four imine-nitrogen atoms comprising the basal plane and an oximate-oxygen atom in the apical position. The copper–imine nitrogen bond lengths (average 1.957 and 1.953 A in 3 and 4, respectively) are shorter than that of the axial copper–oximate oxygen [2.263(3) (3) and 2.242(3) A (4)]. An oxime proton is lost from the ligand in the complex formation, the remaining oxime proton being involved in a hydrogen bond between the peripheral oxime oxygens of the same bis(alkyl)glyoximatocopper(II) unit. The intramolecular copper–copper separation is 3.898(1) (3) and 3.825(1) A (4). Variable-temperature magnetic susceptibility measurements showed the occurrence of intramolecular ferro- (1, 3 and 4) and antiferro-magnetic exchange interactions (2), the singlet–triplet energy gap J being +9.1 (1), -1.9 (2), +1.0 (3) and +3.1 cm -1 (4). The analysis of the exchange pathway through the out-of-plane oximato bond in this family has been substantiated by extended-Huckel calculations and a quasi-linear correlation between the value of J and the angle at the Cu–O–N (α) has been found. The influence of the size of the imine-carbon alkyl substituents on both the nature and magnitude of J is discussed in the light of the available structural information.

A new vicinal-dioxime and its mono and trinuclear complexes containing the monoazatetraoxa macrocyclic moiety

Mononuclear [Co(HL)2L′Cl)], [Co(LBF2)2L′Cl] or [Cu-(HL)2] H2L = {N,N′-bis (4′-N-phenylaza [15]crown-5)diaminoglyoxime} and a trinuclear, [Cu(L)2(CuL′)2](NO3)2, complex of the ligand were synthesized and characterized. The mononuclear copper(II) species coordinates to two copper(II) ions through the deprotonated oximate oxygens to yield a trinuclear structure cis-bridged by the oximate groups, with 1,10-phenanthroline as an end-cap ligand. The terminal copper adopts an essentially planar configuration with the nitrogen atoms of H2L. The structure of the ligand and its complexes is proposed and formulated according to the elemental analyses, 1H- and 13C-n.m.r, i.r. and m.s. spectral data.

Dinuclear copper(II) complexes containing nitroso-oximato bridges: two different copper(II)-bridging entities from the same precursor

The complexes [Cu(μ-L)Cu(bipy)(EtOH)](ClO 4) 2 2a and [Cu(μ- 1L)Cu(bipy)(H 2O)](ClO 4) 2·H 2O 2b [where H 2L = N,N′-bis(1,3-dimethyl-5-nitrosopyrimidine-2,4-(1H,3H)-dion-6-yl)propylenediamine; H 2 1L arises from H 2L by elimination of a CO molecule from one of the pyrimidine rings] have been obtained from the reaction of the precursor [Cu(μ-HL)Cu(H 2O) 2(CH 3CH 2OH)](ClO 4) 3 1 with bipy and Cu(ClO 4) 2 · 6H 2O, respectively. The structures of 2a and 2b have been solved by X-ray crystallographic methods. The structure of 2a is made up of [Cu(μ-L)Cu(bipy)(EtOH)] 2+ cations and two semi coordinated perchlorate anions. The [Cu(I)L] fragment coordinates to the external Cu(2) ion through the two deprotonated oximate oxygens to afford a dinuclear structure with double syn-syn nitroso-oximate bridge and an intramolecular CuCu distance of 3.731(1) Å. The Cu(1) exhibits a CuN 4O 2 pseudoctahedral coordination polyhedron whereas the geometry around the Cu(2) ion is distorted square-pyramidal CuN 2O 2O. The structure of 2b consists of [Cu(μ- 1L)Cu(bipy)(H 2O)] 2+ cations, two perchlorate anions and one lattice water molecule. The coordination of the [Cu( 1L)] unit to the external Cu(2) ion takes place through the two nitroso-oximate groups, one of them disordered on two sets of crystallographic positions, one with a 63% occupancy and the other with a 37% occupancy. The intramolecular Cu(l)Cu(2) distance is 3.655(3) Å. The Cu(l) occupying the inner site of the 1L 2− ligand exhibits a 4+1 CuN 4O (63%) [CuN 3O 2(37%)] coordination environment whereas the Cu(2) atom is in a distorted square-pyramidal CuN 2O 3(63%)[CuN 3O 2(37%)] environment. The dinuclear fragments of 2a and 2b are almost planar with dihedral angles between the mean basal coordination planes of 4.1(2)° and 4.6°, respectively. Both 2a and 2b are diamagnetic at room temperature, so that J < −1000 cm −1. The structural and magnetic data for these complexes have been compared with those of similar compounds, but no correlation between the magnitude of the exchange interaction and the degree of deviation from planarity is evident. In view of this and to rationalize the influence of the distortion from planarity on the magnetic properties in oximate-bridged complexes, MO Extended Hückel calculations have been performed.

Co-ordination of copper(II) and nickel(II) ions by a novel open chain oxime ligand

Potentiometric spectroscopic and X-ray studies of the open chain oxime ligand, N,N′-bis(2-hydroxyimino-propionyl)propane-1,3-diamine and its complexes with NiII and CuII ions showed a very high efficacy of the ligand studied in the co-ordination of both CuII and NiII ions. The metal complexes are very stable and square-planar with four nitrogens involved in metal-ion binding. These complexes may be additionally stabilised by hydrogen bonds between two oxime oxygen atoms.

Structural studies on an iron(III) complex containing (Z)-2-(2-aminothiazol-4-yl)-N-(2-hydroxyethyl)-2-(hydroxyimino)acetamide, a model compound for a cephalosporin antibiotic Cefdinir

(Z)-2-(2-Aminothiazol-4-yl)-N-(2-hydroxyethyl)-2-(hydroxyimino)acetamide (HL) has been employed as a model compound for a cephalosporin antibiotic, Cefdinir. A trinuclear iron(III) complex [Fe3L6]Cl[OH]21 has been obtained from a methanol solution containing HL and FeCl3 and its structure determined by X-ray crystallography: monoclinic, space group P21/n, a= 15.559(1), b= 19.295(2), c= 10.963(1)Å, β= 101.29(1)°, Z= 2. The molecular structure contains a linear Fe(1)–Fe(2)–Fe(1′) arrangement, the central atom Fe(2) being an inversion centre. Atom Fe(1) is co-ordinated to three molecules of L through the thiazole and oximate nitrogen atoms to form Fe(1)L3, and Fe(2) to six oximate oxygen atoms of the two Fe(1)L3 units. The two Fe(1)L3 units are bridged by the central iron atom Fe(2). The Mössbauer spectrum of 1 gave an apparent doublet signal consisting of two doublets, A and B, assigned to Fe(1) and Fe(2), respectively. The isomer shifts δ of these doublets are the same (0.26 mm s–1), and are typical for high-spin iron(III). In addition, the reflectance spectrum did not show any intervalence bands. These spectral data indicate that the three iron atoms are high-spin iron(III). The compound co-ordinates to iron(III)via the thiazole ring nitrogen atom and the oximate nitrogen atom (2N mode) in methanol which is different from that in water, where L prefers to co-ordinate to an iron(III) through the oximate oxygen atom and the amide oxygen atom (2O mode).

Synthesis and crystal structure of a copper(II) complex with a tetradentate dithiadioxime ligand

A neutral five-coordinate dithiadioxime complex of copper(II), chloro[3,3′-(1,3-propanedithia)bis(3-methyl-2-butanone oximato)(1-)- S, S′, N, N′]copper( II) (Cu(LH)Cl), was prepared by reaction of CuCl 2 with the [3,3′-(1,3-propanedithia)bis(3-methyl-2-butanone oxime)] ligand (LH 2) in methanol-acetone. The crystal structure of the Cu(LH)Cl monohydrate, [CuCl(C 13H 25N 2S 2O 2)]·H 2O, reveals a square pyramidal geometry about the metal centre. The copper(II) ion is coordinated in an approximate square plane by the two oxime nitrogen atoms and two thioether sulphur atoms of the tetradentate dithiadioxime ligand, with the chlorine occupying an axial coordination site at a CuCl distance of 2.3931(8) Å. The copper-to-nitrogen distances average 1.997 Å, while the copper-to-sulphur distances average 2.3279 Å. The least-squares S 2N 2 plane is situated 0.467(1) Å below the copper centre. A proton bridges the two oxime oxygen atoms of the complex in the fashion typical of metal complexes containing cis-oxime functions.

Oxamide oxime-based copper(II) coordination polymers. Two- and three-dimensional structures controlled by dicarboxylates

The new Cu(II) complex, [Cu(H 2oao)(L(1,2))(H 2O)] ( 1), and coordination polymers, {[Cu(H 2oao) (L(2,4))]·H 2O} n ( 2) and {[Cu(H 2oao)(Hoao)]·(HL(2,2))} n ( 3) (H 2oao = oxamide oxime; H 2L(1,2) = maloic acid; H 2L(2,4) = succinic acid; H 2L(1,2) = maleic acid), have been synthesized and their structures have been X-ray crystallographically characterized. 1 crystallizes in the monoclinic, space group P2 1/ c with a = 10.186(1), b = 6.648((1), c = 14.748(3) Å, β = 102.06(1)°, U = 976.5(3) A ̊ 3 and Z = 4. The mononuclear units in 1, in which L(1,2) 2− chelates to Cu(II) ions, are linked to form a two-dimensional sheet structure through hydrogen bonds between coordinated H 2oao and L(1,2) 2−. Additional hydrogen bonds link the layers to form a three-dimensional hydrogen bonding network. 2 crystallizes in the monoclinic, space group P2 1/ n with a = 14.739(4), b = 9.994(3), c = 7.101(2) A ̊ , β = 98.52(2)°, U = 1034.4(5) A ̊ 3 and Z = 4. The Cu(II) ions in 2 are bridged by L(2,4) 2− coordinated in an amphimonodentate mode, forming a one-dimensional zigzag chain. The water of crystallization is hydrogen bonded to both L(2,4) 2− and H 2oao of an adjacent chain, forming a two-layered sheet. Further weak hydrogen bonds link another chain, and an extended three-dimensional hydrogen bonding network runs through the crystal. 3 crystallizes in the monoclinic, space group P2 1/ c, with a = 14.817(3), b = 13.693(4), c = 7.328(2) A ̊ , β = 101.10(2)°, U = 1459.1(7) A ̊ 3 and Z = 4. In contrast to the case of 1 and 2, the dicarboxylic acid, L(2,2) 2− in 3 is not coordinated to the Cu(II) ions. The axial coordination of the oximate oxygen in an adjacent Hoao to [Cu(H 2oao)(Hoao)] + leads to the formation of a one-dimensional zigzag chain. The chains are linked by hydrogen bonds between H 2oao on adjacent chains to form sheets, which are sandwiched between uncoordinated HL(2,2) − layers, resulting in a segregated double sheet structure in the crystal. The obtained structures are greatly associated with the size of the spacers, which link the carboxylate groups in the dicarboxylic acids, and hydrogen bonding interactions between the ligands.

Interaction of Cefdinir with Iron in Aqueous Solution.

Cefdinir (CFDN) is an orally active, semisynthetic cephalosporin antibiotic and its structure is characterized by an oxyimino side chain which is able to form complexes with various metal ions. We observed that bioavailability of CFDN in dogs was reduced when it was co-administered with iron(II) salts. To assess possible effects of extraneous iron such as iron supplements on the bioavailability of CFDN, stability constants of the complexes formed between CFDN and iron(II) and iron(III) have been determined in aqueous solution by potentiometric and spectrophotometric titration methods. The stability constants were as follows : log β110=7.53, log β120=14.44, log β130=18.33 for the iron(II) complexes and log β110=10.43, log β120=20.40 and log β130=27.54 for the iron(III) complexes. Theoretical species distribution diagrams as a function of pH for solutions of metal (M) (0.1 mM) and ligand (L) (0.3 mM) showed that M1L1H0 and M1L2H0 existed as major species for the iron(II) system and M1L2H0 and M1L3H0 were main species for the iron(III) system under neutral conditions. From these results it is believed that complex formation in the digestive tract is involved in the reduction of the bioavailability of CFDN in dogs. In addition, spectrophotometric studies indicated that iron(II) coordinated to CFDN via the thiazole-ring and deprotonated oxime nitrogen atoms and iron(III) coordinated via the amide and deprotonated oxime oxygen atoms.

Variation of the exchange interaction in oximato-bridged Cu IIM II dimers (MCu, Ni, Mn). Crystal structure of [Cu(pdmg)Cu(bipy)(H 2O) 2] (ClO 4) 2· H 2O

Three new dinuclear complexes of formula [Cu(pdmg)Cu(bipy)(H 2O) 2](ClO 4) 2·H 2O ( 1), [Cu(pdmg)Cu(terpy)]-(CIO 4) 2 ( 2) and [Cu(pdmg)Ni(cyclam)](ClO 4) 2·H 2O (3) (H 2pdmg=3,3′-aminopropylenedinitrilobis(2-butanoneoxime); bipy=2,2′-bipyridyl; terpy=2,2′:6′,2″-terpyridyl; cyclam=1,4,8,11-tetraazacyclotetradecane) have been synthesized. The structure of 1 has been determined by single-crystal X-ray diffraction. It crystallizes in the monoclinic system, space group P2 1/ a, with a=14.160(3), b=21.300(2), c=10.208(2) Å, β=95.44(2)°, V=3065(2) Å 3, Z=4, D x=1.68 g cm −3, μ(Mo Kα)=16.3 cm −1, F(000)=1584 and T=291 K. A total of 5263 reflections was measured over the range 1 ⩽θ⩽25°; of these, 2057 (independent and with I⩾2σ( I)) were used in the structural analysis. The final R and R w residuals were 0.062 and 0.064, respectively. The structure of 1 is made up of cationic [Cu(pdmg)Cu(bipy) 2(H 2O) 2] 2+ units, non-coordinated perchlorate anions and water of crystallization. The [Cu(pdmg)] fragment coordinates to the second copper(II) ion through its deprotonated oximate oxygens to afford a binuclear structure doubly bridged by the oximate groups in the cis arrangement. The Cu(NO) 2Cu bridging network is bent, the dihedral angle being 151°. The intramolecular metal-metal distance is 3.691(2) Å. The magnetic behavior of 1– 3 was investigated in the temperature range 50–300 K. The values of the exchange coupling constant J (the spin Hamiltonian being Ĥ=- JŜ A·Ŝ B) for 1– 3 were −674, −174 and −204 cm −1, respectively. The influence on the exchange coupling of the orientation of the magnetic orbitals and the number of unpaired electrons involved in the oximato-bridged Cu IIM II dimers (M=Cu, Ni, Mn) are analyzed and discussed.

Vanadium(V), Molybdenum(VI) and Tungsten(VI) Complexes with Hydroxyoximes as Ligands: Formation in Solution, Synthesis and Characterization

Abstract The study in water-ethanol solution of the com-plexation of vanadium(V), molybdenum(VI) and tungsten(VI) by two o-hydroxyoximes, salicylaldoxime (H2SAL) and 2-hydroxybenzophenonoxime (H2BPO), permitted the determination of the composition (metal/1igand–1/2) as well as the apparent stability constants of the species formed in solution. The complexes isolated in powdered form were characterized by methods such as elemental analysis, UV-Vis-IR and NMR spectrometry. A structural hypothesis proposed is that for every complex the coordination number of the central atom is six. The two ligands are bonded bidentately to the metal by the nitrogen of the oxime function and oxygen of the phenolic group. On the other hand, coordination is monodentate in the 1:2 tungsten complexe which contain, in addition to the dioxo function, two chloro anions in the coordination sphere.

Synthesis, structure and magnetism of a tetranuclear Fe(III) complex containing an [Fe 4(μ 3-O) 2] 8+ core

The tetranuclear Fe(III) complex [L 2Fe 2(μ 3-O) 2(μ 2-CH 3COO) 3(Sao) 2Fe 2]X (X=ClO 4, ( 1), PF 6 ( 2)), where L is the cyclic amine 1,4,7-trimethyl-1,4,7-triazacyclononane and Sao is the dianion of salicylaldoxime (H 2Sao), has been synthesized and characterized on the basis of elemental analysis, IR, electronic, Mössbauer spectroscopy and variable-temperature (4–285 K) magnetic susceptibility measurements. The molecular structure has been established by X-ray diffraction of 2. The structure consists of an [Fe 2 wing(μ 3-O) 2Fe 2 body] 8+-butterfly core. Each Fe(III) ion is in a distorted octahedral environment. The two Fe(Sao) + units function as bridges between two terminal ‘wing’ iron ions through their deprotonated oximate oxygen and represent the ‘body’ iron ions in the tetranuclear core. Three acetate groups are singly bridging between the iron ions. Mössbauer spectra display two quadrupole doublets, consistent with two different high-spin ferric sites. Magnetic susceptibility measurements reveal a diamagnetic ground state with antiferromagnetic exchange interactions among the four high-spin ferric centers. The exchange coupling constant J 12 (‘body-body’ interaction) could not be determined due to prevailing spin frustration, but the ‘wing-body’ antiferromagnetic interaction, J, was evaluated to be −46 cm −1 [ H̆=−2 J( S̆ 1· S̆ 3+ S̆ 2· S̆ 3+ S̆ 1· S̆ 4+ S̆ 2· S̆ 4)−2 J 12 S̆ 1· S̆ 2].

The influence of pH on the coordination of copper(II) by 2-amino-2-deoxy- D-gluconate and 2-amino-2-deoxy- D-glucose oxime as studied by 1H and 13C NMR relaxation rate measurements and EPR spectroscopy

Copper(II) binding to the D-glucosamine derivatives 2-amino-2-deoxy- D-gluconate and 2-amino-2-deoxy- D-glucose oxime has been studied by 13C and 1H NMR relaxation rate measurements, visible and EPR spectroscopy, at two different pH values. From the Cu(II) induced relaxation rate enhancements distance information of the Cu(II) metal ion to the carbon nuclei of the ligands has been obtained, strongly affirming and further revealing the coordination mode of the ligands to Cu(II) as indicated by the visible and EPR measurements. It is shown that the coordination of the compounds is dependent on the pH. At pH 6.9, Cu(II) forms 1:2 complexes with 2-amino-2-deoxy- D-gluconate in which the copper is bound via two carboxylate and two amino groups at about equal distances, with the C3 hydroxyl groups probably hydrogen bonded to axially located water molecules. At pH 10.7 the ligand is interacting with the amino and C3 hydroxyl group in a nearly square plane and the carboxylate group is possibly in the axial position. Concerning the 2-amino-2-deoxy- D-glucose oxime only the E isomer coordinates to copper. At pH 6.9 Cu(II) complexes are formed wherein the ligand binds in a didentate fashion via the amino and oxime nitrogen. At pH 10.7, there is substantial contribution of a complex wherein the Cu(II) is monodentately bound via the oxime oxygen.

Oximato complexes. Part 1. Solution study, synthesis, structure, spectroscopic and magnetic properties of polynuclear copper(II) complexes containing dimethylglyoxime

Copper(II) complexes of composition [Cu2(Hdmg)2(H2dmg)(H2O)2][ClO4]2·H2O 1, [Cu2(dmg)(Hdmg)(H2dmg)]ClO4·1.5H2O 2 and [Cu3(dmg)2(H2dmg)2][ClO4]2·2H2O 3(H2dmg = dimethylglyoxime) were obtained. The crystal structure of complex 1 was solved by single-crystal X-ray diffraction. It crystallizes in the monoclinic system, space group P21/n, with a= 15.991(3), b= 11.682(1), c= 14.363(4)A, β= 90.82(5)° and Z= 4. The structure consists of cationic dinuclear [Cu2(Hdmg)2(H2dmg)(H2O)2]2+ units, unco-ordinated perchlorate anions and lattice water. The Cu(H2dmg)2+ fragment co-ordinates to the second copper(II) ion through the depronated oximate oxygens of Cu(Hdmg)2 to afford a dinuclear structure doubly bridged by the oximate groups in a cis arrangement. The intramolecular Cu(1)⋯ Cu(2) separation is 3.526(4)A. The configuration about the copper atoms is a distorted square pyramid: the basal plane for Cu(1) comprises two nitrogens of H2dmg and two oximate oxygens whereas that of Cu(2) is formed by four nitrogens of two Hdmg– groups; a water molecule occupies the apical position in both cases. Variable-temperature magnetic susceptibility measurements (50–300 K) on complexes 1–3 revealed the occurrence of a very strong intramolecular antiferromagnetic interaction through the oximate bridges. The formation of mononuclear, dinuclear and trinuclear copper(II) dimethylglyoxime complexes have been observed by spectrophotometry in ethanolic solutions of copper(II) perchlorate and [Cu(Hdmg)2]. A rational scheme accounting for the nature of the existing species has been proposed in the light of the coupled solution–solid state studies.

Oximato complexes. Part 2. Dinuclear dimethylglyoximato complexes of copper(II) with a new co-ordination mode of the oximate ligand

There new dinuclear copper(II) complexes of formula [Cu2(dmg)(Hdmg)(H2dmg)]Cl·H2O 1, [Cu2(dmg)(Hdmg)(H2dmg)]ClO42 and [{Cu2(dmg)(Hdmg)(H2dmg)}2(SO4)]·2.52O 3(H2dmg = dimethylglyoxime) have been synthesised. The crystal structure of 3 was solved by single-crystal X-ray diffraction methods: monoclinic, space group C2/c, a= 22.736(2), b= 21.367(12), c= 11.781(7)A, β= 122.97(5)° and Z= 4. The structure consists of two cationic binuclear [Cu2(dmg)(Hdmg)(H2dmg)]+ units bridged by a sulfate anion, leading to a neutral tetrameric entity, and lattice water. In the dinuclear cation the copper(II) ions are bridged by two oximate groups, one through the nitrogen and oxygen atoms and the other only through the oxygen atom. The intramolecular Cu(1)⋯ Cu(2) distance is 3.266(2)A. The geometry around the copper atoms is a distorted square pyramid: the basal plane for Cu(1) comprises three nitrogen and one oxygen atom of the Hdmg– and dmg2– groups, whereas that of Cu(2) is formed by two nitrogens of H2dmg and two oximate oxygens; two oxygen atoms from a sulfate ion occupy the apical position of each copper atom. The temperature dependence of the molar magnetic susceptibility (100–300 K) for 1–3 reveals a very strong intramolecular antiferromagnetic coupling between copper(II) ions (J ca.–950 cm–1).

Synthesis and X-Ray Structures of Ni(II) Complexes of 1-(2-Pyridinyl)Ethanone Oxime

Abstract A study of the complexation of Ni(II) with 1-(2-pyridinyl)ethanone oxime as a function of pH was carried out. A green complex, dibromobis(1-(2-pyridinyl)ethanone oxime)nickel(II), was isolated at pH 3. This octahedral complex (1) crystallizes in space group P21/n (a = 8.754(2), b = 11.136(3), c = 18.210(4) A, β = 92.18(2)[ddot], Z = 4) and has cis bromide ions (av. Ni-Br = 2.57(2) A), cis pyridine nitrogens (av. Ni-N = 2.091(9) A), and trans oxime nitrogens (av. Ni-N = 2.043(7) A). An orange octahedral complex, diaquo(1-(2-pyridinyl)ethanone oxime)(1-(2-pyridinyl)ethanone oximato)nickel(II) nitrate, (2) crystallized at pH 6 in space group P21/c (a = 12.497(3), b = 7.501(2), c = 20.940(5) A, β = 95.59(2)[ddot], Z = 4) and has trans water molecules (av. Ni-O = 2.069(5) A), cis pyridine nitrogens (av. Ni-N = 2.109(5) A, and cis oxime nitrogens (av. Ni-N = 2.037(6) A). Complex (2) has a short intramolecular hydrogen bond between oxime oxygen atoms (O…O = 2.524(3) A). A dark reddish-brown complex form...

Binuclear metal complexes. Part III. Complexes of 1-hydroxy-2, 3-dimethyl-5-carboxylato-1,4-diaza-1,3-pentadiene and 1-hydroxy-2,3-dimethyl-4(2?-carboxyphenyl)-1,4-diaza-1, 3-butadiene with bivalent transition metal ion complexes

Binuclear complexes of the type [M(HDCDP)(H2O)n]2 and [M(HDCDB)(H2O)n]2, where HDCDP and HDCDB are Schiff bases derived from glycine and diacetylmonoxime, and orthoaminobenzoic acid and diacetylmonoxime respectively, M=VOII, CoII, NiII, CuII or AgII and n=0 or 2, have been synthesized. Physical and spectroscopic analyses indicate a binuclear structure for the complexes with metal ions in an octahedral environment, where the ligands coordinate to the metal centre through azomethine nitrogens, oxime and carboxylate oxygen in a tetradentate manner.

Conformation of three tetrahydropyridinyl oxime cognition activators

The conformational features of three tetrahydropyridinyl oxime cognition activators 1-(1-methyl-1,2,5,6-tetrahydro-3-pyridinyl)ethanone oxime·HCl (I), 1-(1-methyl-1,2,3,6-tetrahydro-4-pyridinyl)ethanone oxime·HCl (II), and 1-(1,2,5,6-tetrahydro-3-pyridinyl)ethanone O-methyloxime HCl(III) were analyzed by X-ray diffraction and the quantum mechanical semiempirical PM3 methods. Results indicate that in the solid state the drugs exhibit “anti-syn” isomerism, with the substituent at the oxime oxygen atomanti oriented in respect to C=N. This arrangement also represents a low-energy situationin vacuo, as confirmed at the PM3 level, although another low-energy conformation (“clinal-anti”) could be of significance in the conformational energetics of the drugs.

Binuclear Metal Complexes IV. Copper (II), Cobalt (II) and Nickel (II) Complexes with 1-Hydroxy-2, 3-dimethyl-6-amino-6-mercapto-1,4,5-triaza-1, 3-hexadiene (HDAMTH)

Abstract A few homo-binuclear metal complexes of the type [(HDAMTH)M(H2 O)2]2 X?; where HDAMTH = a Schiffs base obtained by the condensation of thiosemicarbazide and diacetylmonoxime, M = copper(II), nickel(II) and cobalt(II) and X = Cl−, Br−, Ac−, NO3 −, ClO− 4, SO– 4 etc. have been isolated. Infrared spectra of the complexes suggest that the ligand coordinates to the metal ion through its azomethine nitrogen, oxime oxygen and thionyl sulphur. The water molecules seem to be coordinated as evidenced from IR and thermal analyses of the complexes. The complexes have high molar conductance values. Reflectance spectra of the complexes indicate octahedral geometry around the metal ions. Different crystal field parameters such as B, β, etc. for the cobalt(II) and nickel(II) complexes have also been calculated.

Synthesis of an ether oxime ligand and its rhodium(III) complex, and X-ray structure of the rhodium(III) complex: Unique rhodium(III) bonding to a simple ether

The ligand 3-methoxy-3-methyl-2-butanone oxime and its rhodium(III) complex have been synthesized, and the complex has been structurally characterized. The octahedron around the rhodium atom involves two trans-chlorine atoms [RhCl = 2.3236(8) Å], two cis-oxime nitrogen atoms [av. RhN = 1.958(3) Å] and two cis-ether oxygen atoms [av. RhO = 2.117(3) Å]. The oxime oxygen atoms are involved in a short intramolecular hydrogen bond (OO = 2.391 Å). Synthesis and characterization of the ligand and the rhodium(III) complex are described, and the 1H NMR results are given and discussed. To our knowledge this is the first characterized ether oxime metal complex.