Metallionenaustausch im System Acetylacetonat/Halogenid/Tetrahydrofuran

Exchange of Metal Ions in the System Acetylacetonate/Halide/Tetrahydrofuran . As bifunctional Lewis bases metal bis(acetyl-acetonates) react with zinc(II) chloride under formation of binuclear complexes (THF)₂M(acac)₂ZnCl₂ (M = Ni, Co, Mg). The octahedral and the tetrahedral centre of these compounds are connected by tridentate oxygen atoms of the two acetylacetonato ligands which are simultaneously part of a four-membered ring MOZnO. The addition is combined with a deformation of the octahedral centre, as a prerequisite of a closest package of the atoms within the MOZnO ring. With mercury(II) chloride the metal bis(acetylacetonates) react as tetrafunctional Lewis bases. In the trinuclear complexes (THF)₂M(acac)₂(HgCl₂)₂ (M = Co, Ni, Mg) the interaction between the three coordination centres is weak. No structural change of the octahedral centre (THF)₂M(acac)₂ is found, but the HgCl₂ group diverge slightly from linearity. A ligand exchange was observed in the following cases:

• (a) Reaction of vanadium(III) chloride with Co(acac)₂ under formation of [(THF)₂V(acac)₂][(THF)CoCl₃] (transition of the acetylacetonato ligands to the higher valent central atom).
• (b) Reaction of magnesium halides with M(acac)₂ and formation of (THF)₃Mg(acac)₂MX₂
• (c) Formation von (THF)₃Co(acac)(μ—C1)ZnC1₂ (V) by the reaction of Zn(acac)₂ with cobalt(l1) chloride

In the complex V the octahedral ccntrc of cobalt(II) is connected with the tetrahedral centre of zinc(I1) by tridentate oxygen atom of the acetylacetonato ligand and a chloro bridge (formation of the four-membered CoClZnO cycle with a closest package of the atoms). A driving force for reaction c is the formation of the stable tetrahedral OZnCI₃ group. Important for the li- gand exchange according to c is the stability of the octa- hcdral MgO₆ moiety and the easy formation of the tetra- hedral MO₂X₂ group with a transition metal ion. (THF)₃Co(acac)(μ-CI)(HgCl₂) (VI) is isoslruclural with V. But there is a marked diffcrence between the bond angles of the tetrahedral central atom including the termi- nal chloro ligands (120.7° for V; 143.7° for VI). The crystal structure of (THF)₃Co(acac)(μ-CI)ZnCl₂ (V) was determined by X-ray diffraction: monoclinic; space group P2,/n; Z = 4; a = 1 177.4(5); b = 1628.9(4); c = 1284.2(6) pm; β = 99.54(4)°; R = 6.71 % for 2160 observed reflections.     

Struktur und thermischer Abbau von Bis (1,3-diketonato) cobalt-bisimidazolen

Structure and Thermal Degradation of Bis(1,3-diketonato)cobaltbisimidazoles The crystal structure of Co(bzac)₂(HIm)₂. 2MeOH ( I ) and Co(acac)₂(HIm)₂ ( II ) were determined by x-ray diffraction. II : triclinic, space group P1 , Z = 2, a = 746.3(1), b = 948.2(1), c = 1396.7(2)pm, α = 85.18(1)°, β = 88.96(1)°, γ = 80.72(1)°, R = 3.0% for a total of 2194 observed reflections. I : monoclinic, P2₁/c, Z = 2, a = 964.2(3), b = 864.5(2), c = 1769.8(4)pm, β = 98.87(2)°, R = 4.7% for a total of 967 observed reflections. In both compounds centrosymmetric molecules with two bidentate diketonato groups and two imidazole ligands in trans-position are present. The molecules of II are linked by N? H…?O-bridges within layers, while in the lattice of I by the interaction with methanol molecules N-H…?O-H…?O-bridges are formed. The nature of the H-bridges is the deciding factor for the first step of the thermal degradation of the complexes. The N-H…?O-bridges of II relieves the change of the acidic protons of the imidazole to the acetylacetonato ligands. Therefore in the first step acetylacetone is eliminated. No such bridges are present in the complex I . Therefore, in the first step, imidazole and methanol are removed. On heating in O-donor solvents the reaction of I is quite analogous, and this is the reason for the application of this complex as a latent initiator of the epoxide polymerisation.     

Polysulfonylamine. LXIX. Neuartige Pniktogendisulfonylamide: Synthese von Bismutdimesylamiden und Kristallstrukturen des zwölfgliedrigen Cyclodimers [Ph2BiN(SO2Me)2]2 und des ionischen Komplexes [H(OAsPh3)2]⊕(MeSO2)2N⊖

Polysulfonyl Amines. LXIX. Novel Pnictogen Disulfonylamides: Synthesis of Bismuth Dimesylamides and Crystal Structures of the Twelve-Membered Cyclodimer [Ph₂BiN(SO₂Me)₂]₂ and of the Ionic Complex [H(OAsPh₃)₂]^⊕(MeSO₂)₂N^? The novel bismuth(III or V) disulfonylamides Ph₂BiN(SO₂Me)₂ ( 1 ), PhBi[N(SO₂Me)₂]₂ ( 2 ), PhBi[N(SO₂Me)₂]Br ( 3 ), Bi[N(SO₂Me)₂]₂Cl ( 4 ), Bi[N(SO₂Me)₂]Cl₂ · 12-crown-4 ( 5 ) and Ph₃Bi[N(SO₂Me)₂]Cl ( 6 ) were obtained by acidolysis of Ph₃Bi with HN(SO₂Me)₂ (→ 1 ), by metathesis of AgN(SO₂Me)₂ with Ph₂BiCl (→ 1 ) or PhBiBr₂ (→ 2, 3 ), by condensation of BiCl₃ with Me₃SiN(SO₂Me)₂ (→ 4 ; in presence of 12-crown-4: → 5 ), or by oxidative addition of ClN(SO₂Me)₂ to Ph₃Bi (→ 6 ). Independently of the molar ratio employed, triphenylarsane oxide and dimesylamine form the crystalline 2/1 complex [H(OAsPh₃)₂]^⊕(MeSO₂)₂N^? ( 7 ). The crystal packing of 7 (monoclinic, space group C2/c) consists of discrete cations displaying crystallographic C_i symmetry and a strong O …? H …? O hydrogen bond (H atom located on a centre of symmetry, O …? O′ 241.2 pm, As? O …? O′ 120°, As? O 168.3 pm), and chiral anions with crystallographic C₂ symmetry (N? S 157.3 pm, S? N? S 122,9°). In the solid state, the bismuth(III) compound 1 (triclinic, space group P1 ) is a cyclodimer with crystallographic C_i symmetry, in which two Ph₂Bi^⊕ cations are connected through two (α-O, ω-O)-donating dimesylamide ligands to form a roughly twelve-membered [BiOSNSO]₂ ring (Bi? O 239.7 and 246.6, O? S 148.0 and 145.4, S? N 157.7 and 159.2 pm, Bi? O? S 126.6 and 127.5°). The bismuth atom adopts a pseudo-trigonal-bipyramidal geometry (O? Bi? O 165.4, C? Bi? C 93.0, O? Bi? C 83.8 to 86.5°). The essentially similar conformations of the discrete anion in 7 and of the bidentate bridging ligand in 1 are discussed in detail.     

Synthese und Struktur der Cobalt(III)-Komplexe 14gliedriger cis- und trans-N2S2-Dibenzomakrocyclen mit zwei koordinierenden Acetatogruppen

Synthesis and Structure of Cobalt(III) Complexes of 14-Membered cis- and trans-N₂S₂ Dibenzo Macrocycles with two Pendant Acetato Groups The isomeric fourteen membered macrocyclic ligands 6,7,9,15,16,18-hexahydrodibenzo[f,m][1,8]dithia[4,11]diazacyclotetradecine-8,17-diacetic acid-0.5-hydrate (H₂L³), C₂₂H₂₆N₂O₄S₂ · 0.5 H₂O and 6,7,13,15,16,18-hexahydrodibenzo-[e,m][1,4]dithia[8,11]diazacyclotetradecine-14,17-diacetic acid-1.5-hydrate (H₂L⁶), C₂₂H₂₆N₂O₄S₂ · 1.5 H₂O with cis- and trans-N₂S₂ donorsets and two pendant acetato groups form the stable complexes [Co(L³)]ClO₄ · 2 H₂O ( 1 ) and [Co(L⁶)]ClO₄ · H₂O ( 2 ). Co(III) is octahedrally coordinated herein to all six donor centers of the respective ligand. The macrocyclic rings are folded. The metal ions are located outside the macrocyclic cavity. The mean Co? N, Co? O and Co? S distances are 196, 190 and 224 pm, respectively. Crystal data: 1 , monoclinic, space group C2/c, a = 3 797.7(9), b = 763.8(3), c = 2 207.0(7) pm, β = 123.17(2), Z = 8, 3 445 reflections, R(R_w) = 0.072(0.070); 2 , monoclinic, space group C2/c, a = 3 197.1(6), b = 880.4(2), c = 1 890.6(4) pm, β = 112,19(3)°, Z = 8, 4 415 reflections, R(R_w) = 0.062(0.064).     

Synthesis,structures, and characterization of copper(II), nickel(II), and cobalt(III) metal complexes derived from an asymmetric bidentate Schiff-base ligand

An asymmetric bidentate Schiff-base ligand (2-hydroxybenzyl-2-furylmethyl)imine (L–OH) was prepared. Three complexes derived from L–OH were synthesized by treating an ethanolic solution of the appropriate ligand with an equimolar amount of metallic salt. Three complexes, Cu₂(L–O^?)₂Cl₂ (1), Ni(L–O^?)₂ (2) and Co(L–O^?)₃ (3), have been structurally characterized through elemental analysis, IR, UV spectra and thermogravimetric analysis. Single crystal X-ray diffraction shows metal ions and ligands reacted with different proportions 1?:?1, 1?:?2 and 1?:?3, respectively, so copper(II), nickel(II), and cobalt(III) have different geometries.     

Polysulfonylamine. XXXVII. Darstellung von Quecksilberdimesylamiden. Kristall- und Molekülstrukturen von Hg[N(SO2CH3)2]2, Hg[{N(SO2CH3)2}2(DMSO)2] und Hg[{N(SO2CH3)2}2(HMPA)]

Polysulfonyl Amines. XXXVII. Preparation of Mercury Dimesylamides. Crystal and Molecular Structures of Hg[N(SO₂CH₃)₂]₂, Hg[{N(SO₂CH₃)₂}₂(DMSO)₂], and Hg[{N(SO₂CH₃)₂}₂(HMPA)] Hg[N(SO₂CH₃)₂]₂ ( 1 ) and Hg₂[N(SO₂CH₃)₂]₂ ( 2 a ) are formed as colourless, sparingly soluble precipitates when solutions of Hg(NO₃)₂ or Hg₂(NO₃)₂ in dilute nitric acid are added to an aqueous HN(SO₂CH₃)₂ solution. By a similar reaction, Hg₂[N(SO₂C₆H₄ ? Cl? 4)₂]₂ is obtained. 1 forms isolable complexes of composition Hg[N(SO₂CH₃)₂]₂ · 2 L with L = dimethyl sulfoxide (complex 3 a ), acetonitrile, dimethyl formamide, pyridine or 1,10-phenanthroline and a (1/1) complex Hg[N(SO₂CH₃)₂]₂ · HMPA ( 4 ) with hexamethyl phosphoramide. Attempted complexation of 2 a with some of these ligands induced formation of Hg⁰ and the corresponding Hg^II complexes. Crystallographic data (at -95°C) are for 1: space group 14₁/a, a = 990.7(2), c = 2897.7(8) pm, V = 2.844 nm³, Z = 8, D_x = 2.545Mgm^?3; for 4a: space group P1 , a = 767.8(2), b = 859.2(2), c = 925.2(2)pm α = 68.44(2), β = 86.68(2), γ = 76.24(2)°, V = 0.551nm³, Z = 1, D_x = 2.113 Mgm^?3; for 4: space group P2₁/c, a = 1041.3(3), b = 1545.4(3), c = 1542.5(3) pm, β = 100.30(2)°, V = 2.474nm³, Z = 4, D_x = 1.944Mgm³. The three compounds form molecular crystals. The molecular structures contain a linear or approximately linear, covalent NHgN moiety; the Hg? N distances and N? Hg? N angles are 206.7(4) pm and 176.3(2)° for 1, 207.2(2) pm and 180.0° for 3a, 205.7(4)/206.7(4) pm and 170.5(1)° for 4. In the complexes 3a and 4, the 0-ligands are bonded to the Hg atoms perpendicularly to the N? Hg? N axes, leading in 3a to a square-planar trans-(N₂O₂) coordination with Hg? 0 261.2(2) pm and N? Hg? O 92.3(1)/87.7(1)°, in 4 to a slightly distorted T-shaped (N₂O) geometry with Hg? 0 246.2(4)pm and N? Hg? 0 96.7(1)/92.0(1)°. In all three structures, the primary coordination is extended to a severely distorted (N₂O₄) hexacoordination by the appropriate number of secondary, inter- and/or intramolecular Hg…?0 inter-actions (0 atoms from sulfonyl groups, Hg…?O distances in the range 280—300pm). The intramolecular Hg…?O interactions give rise to nearly planar four-membered [HgNSO] rings. The molecule of 1 has a two-fold axis through the bisector of the N? Hg? N angle, the molecule of 3a an inversion center at the Hg atom. The molecule of 4 has no symmetry.     

Kinetics of Reduction of Some Surfactant-Cobalt(III) Complexes by Iron(II)

The electron transfer kinetics of the reaction between the surfactant-cobalt(III) complex ions, cis-[Co(en)₂(C₁₂H₂₅NH₂)₂]³⁺, cis-α-[Co(trien)(C₁₂H₂₅NH₂)₂]³⁺(en:ethylenediamine, trien:triethylenetetramine, C₁₂H₂₅NH₂ : dodecylamine) by iron(II) in aqueous solution was studied at 298, 303, 308 K by spectrophotometry method under pseudo-first-order conditions using an excess of the reductant in self-micelles formed by the oxidant, cobalt(III) complex molecules, themselves. The rate constant of the electron transfer reaction depends on the initial concentration of the surfactant cobalt(III) complexes. ΔS^# also varies with initial concentration of the surfactant cobalt(III) complexes. By assuming outer-sphere mechanism, the results have been explained based on the presence of aggregated structures containing cobalt(III) complexes at the surface of the self-micelles formed by the surfactant cobalt(III) complexes in the reaction medium. The rate constant of each complex increases with initial concentration of one of the reactants surfactant-cobalt(III) complex, which shows that self micelles formed by surfactant-cobalt(III) complex itself has much influence on these reactions. The electron transfer reaction of the surfactant-cobalt(III) complexes was also carried out in a medium of various concentrations of β-cyclodextrin. β-cyclodextrin retarded the rate of the reaction.     

Synthesis and characterization of picolinato and nicotinato cobalt(II) complexes containing tris(2-benzimidazolylmethyl)amine

Two new mononuclear cobalt(II) complexes [Co(ntb)(pic)](ClO₄) · (CH₃OH)_2.35 (1) and [Co(ntb)(nic)](ClO₄) · CH₃OH (2) were synthesized and structurally characterized, where ntb is tris(2-benzimidazolylmethyl)amine, pic is the anion of picolinic acid, and nic is the anion of nicotinic acid. The X-ray analysis indicates that the Co(II) center is six-coordinate in distorted octahedral and five-coordinate in distorted trigonal bipyramidal geometry for 1 and 2, respectively. In 1, the picolinate anion coordinates to Co(II) in a bidentate μ₂-N,O chelating mode. In 2, the nicotinate anion coordinates with Co(II) through a monodentate carboxylate oxygen. 1-D chain structures were formed by intermolecular hydrogen bonds in the two complexes and π–π interactions are important for the stabilization of the structures.     

Novel 2-aminoimidazole-4-one complexes of copper(II) and cobalt(II): Synthesis,structural characterization and cytotoxicity

A series of 2-aminosubstituted (5Z)-3-phenyl-5-(pyridine-2-ylmethylene)-3,5-dihydro-4H-imidazole-4-ones (L) was prepared by the reaction of the corresponding 2-alkylthio-3,5-dihydro-4H-imidazole-4-ones with morpholine or piperidine in the presence of ytterbium(III) triflate. The resulting ligands were subsequently reacted with CuCl₂·2H₂O and CoCl₂·6H₂O to give the corresponding copper(II) and cobalt(II) complexes, respectively. Analysis revealed that the complexes were formed with an LMCl₂ (M = Cu, Co)-type composition in all cases. The structures of the three cobalt complexes prepared in this way were determined by X-ray crystallography. The results revealed that the cobalt ions in these complexes were tetrahedrally coordinated to two chloride anions and two nitrogen atoms from the pyridine and imidazole moieties of the ligand. The electrochemical properties of the ligands and their complexes were evaluated by cyclic voltammetry, and the results revealed that the first stage in the reduction of the Co(II) and Cu(II) complexes involved the reversible formation of the corresponding Co(I) and Cu(I) complexes, respectively. The cytotoxicity activities of the organic ligands and their complexes were evaluated against several cancer cell lines, including MCF-7, A549 and HEK293 cells. The copper complexes of the organic ligands bearing a phenyl or allyl moiety at their N(3) position together with a piperidine substituent at the 2-position of their imidazolone ring exhibited the greatest cytotoxicity of all of the compounds tested in the current study.     

Coordination properties of 4(5)-hydroxymethylimidazole and 4(5)-hydroxymethyl-5(4)-methylimidazole towards cobalt(II) ions

Two new complexes of imidazole alcohols, 4-hydroxymethylimidazole (4-CH₂OHim) and 4-hydroxymethyl-5-methylimidazole (4-CH₂OH-5-CH₃im), with cobalt(II) of formula [CoL₂(H₂O)₂](NO₃)₂ were obtained. These compounds were described through single X-ray diffraction studies, spectroscopic (Ir. Far-IR, UV-Vis-NIR) and magnetic measurements. In the present complexes imidazole ligands are bidentate coordinating the heterocyclic ring through pyridine-like nitrogen and the oxygen atom of the hydroxymethyl group (chromophore CoN₂O₄). The shape of Co(II) coordination polyhedra is that of a distorted octahedron, with the equatorial plane defined by the 4-CH₂OHim (or 4-CH₂OH-5-CH₃im) bidentate ligands and two water molecules occupying axial positions (i.e. trans to each other). Formation of successive cobalt(II) complexes with 4-CH₂OH-5-CH₃im in aqueous solution was followed quantitatively by potentiometry.     

Synthesis,characterization, electrochemical and crystal structure investigation of bis(2-((2-aminoethylimino)methyl)-6-methoxyphenolato) cobalt(III)

The mononuclear cobalt(III) complex [Co(L)₂]Cl ·?H₂O (1) (where L is H₂N(CH₂)₂N=CC₆H₃(OMe)(O^?)) has been prepared and characterized by IR, UV-Vis spectroscopy, conductivity measurements, elemental analysis, TGA, cyclic voltammetry and an X-ray structure determination. The cobalt(III) coordination sphere in [Co(L)2] is cis-CoN₄O₂ with the NNO ligands. Electrochemical studies of 1 using cyclic voltammetry indicate an irreversible cathodic peak (E _pc, ca ?0.60 V) corresponding to reduction of cobalt(III) to cobalt(II).     

Zur Addition von Übergangsmetallhalogeniden an Acetylacetonate zweiwertiger Metallionen

Addition of Transition Metal Dihalides to Acetylacetonates of Divalent Metal Ions Transition metal dihalides ^aM^IIX₂ (FeCl₂, CoCl₂ NiBr₂ etc.) are added by the chelates M^II(acac)₂ under formation of binuclear complexes (THF)₂M^II(acac)₂(^aM^IIX₂). The octahedral and the tetrahedral centre of these compounds are connected by tridentate oxygen atoms of the two acetylacetonato ligands which are simultaneously included in four-membered rings (M^IIOM^II). The addition is combined with a deformation of the octahedral centre, as a prerequisite of a closest package of the atoms within the M^IIOM^II-ring. In the trinuclear complex (THF)₂Ni(acac)₂(HgCl₂)₂ III the interaction between the three coordination centres is weak. No structural change of the octahedral centre (THF)₂Ni(acac)₂ is found, but the HgCl₂-groups diverge slightly from linearity (Cl? Hg? Cl 171.1°). No binuclear complexes with a central ion of the oxidation state III in the octahedral centre were obtained. One reason is the lowered donor strength of the bidentate Lewis base function of the octahedral centre [(THF)₂Mⁿ⁺(acac)₂]^n-2 with M⁺³ as a centralatom. Reacting systems with di- and trivalent ions prefer ionic complexes, as it is shown by the formation of [(THF)₂V(acac)₂][(THF)CoCl₃] IV from VCl₃ and Co(acac)₂. The crystal structures of (THF)₂Co(acac)₂CoCl₂ II and [(THF)₂V(acac)₂][(THF)CoCl₃] IV were determined by x-ray diffraction. II : orthorhombic-primitive; space group P2₁2₁2₁, Z = 4; a = 967.4(2), b = 1453.4(3), c = 1715.9(4) pm; R = 0.049 for 3084 observed reflections. IV : triclinic; space group P1, Nr. 2; Z = 2; a = 871,5(2), b = 930,6(3), c = 1865,6(6) pm; α = 101,70(2), b? = 92,45(2), γ = 91,06(2)°; R = 0,060 für 4221 observed reflections.     

cis-bis(Saccharinato)cobalt(II) and -zinc(II) complexes with 2-dimethylaminoethanol: syntheses,crystal structures,spectroscopic and thermal studies

2-Dimethylaminoethanol (dmea) reacted with tetraaqua-bis(saccharinato)cobalt(II) and -zinc(II) in n-butanol to yield the new complexes cis-[Co(sac)₂(dmea)₂] (1), and cis-[Zn(sac)₂(dmea)₂] (2) (sac?=?saccharinate). The complexes were characterized by elemental analyses, IR spectroscopy, DTA-TG and X-ray crystallography. Both complexes are isomorphous and crystallize in the monoclinic space group P2₁/c. The cobalt(II) and zinc(II) ions are coordinated by two neutral dmea ligands and two sac anions in a distorted octahedral environment. The dmea ligand acts as a bidentate N, O donor through the amine N and hydroxyl O atoms, while the sac ligand exhibits non-equivalent coordination, behaving as an ambidentate ligand; one coordinates to the metal via the carbonyl oxygen atom, while the other is N-bonded. The packing of the molecules in the crystals of both complexes is achieved by aromatic π(sac)–π(sac) stacking interactions, C–H?·?π interactions and weak intermolecular C–H?·?O hydrogen bonds involving the methyl groups of dmea and the sulfonyl oxygen atoms of the sac ligands. IR and UV spectra and thermal analysis are in agreement with the crystal structures.     

Polysulfonylamine. XLI. Ein Silber(I)-Hydrat ungewöhnlicher Zusammensetzung: Röntgenstrukturanalytische und thermochemische Charakterisierung von Tetrakis(dimesylamido)aquatetrasilber(I) [Ag4(N(SO2CH3)2}4(H2O)]

Polysulfonyl Amines. XLI. A Silver(I) Hydrate with an Unusual Composition: Characterization of Tetrakis(dimesylamido)aquatetrasilver(I) [Ag₄(N)SO₂CH₃)₂}₄(H₂O)] by X-Ray Diffraction and Thermal Analysis The title compound is obtained by crystallizing AgN(SO₂CH₃)₂ from water at room temperature. Crystallographic data (at ?95°C): Triclinic space group P1 , a = 864.6(4), b = 1 211.2(5), c = 1 399.1(5) pm, α = 90.97(3), β = 90.90(3), γ = 98.25(4)°, V = 1.4496 nm³, Z = 2, D_x = 2.608 Mg m^?3. The four independent silver atoms and the water molecule form zigzag chains Ag(1)-Ag(2)-(μ-H₂O)-Ag(3) …? Ag(4) …? Ag(1′) with distances Ag(1)-Ag(2) 309.7, Ag(2)-O(w) 241.8, O(w)-Ag(3) 241.4, Ag(3) …? Ag(4) 342.9, Ag(4) …? Ag(1′) 361.4 pm. The catenated silver atoms are further connected by the dimesylamide anions acting as tridentate bridging (α-O, N, ω-O)-ligands. The resulting strands are interconnected into layers through one O(S)-Ag′ contact (247 pm) and one hydrogen bond O(w)-H(l) …? O′(S) per repeating unit. Between the layers, a weak O(S) …? Ag″ interaction (271 ptn) and a hydrogen bond O(w)-H(2) …? O(S) per repeating unit are observed. The silver atoms Ag(l) to Ag(4) display the coordination numbers 5 [NO,Ag(2), distorted trigonal bipyramid], 5[NO₂,O(w)Ag(I), distorted trigonal bipyramid], 5[O₄,O(w), trigonal bipyramid], and 2 + 1 (N₂, li-near; plus a secondary Ag …? 0 contact). The dehydration of the title compound and a solid-solid phase transformation in anhydrous AgN(SO₂CH₃)₂, were quantitatively investigated by thermoconductometry and time- and temperature-resolved X-ray diffractometry (TXRD).     

Spectral characterization and antimicrobial activity of Cu(II) and Fe(III) complexes of 2-(5-Cl/NO2-1H-benzimidazol-2-yl)-4-Br/NO2-phenols

The compounds of 2-(5-chloro/nitro-1H-benzimidazol-2-yl)-4-bromo/nitrophenols (HL_X : X = 1–4) and their copper(II) nitrate and iron(III) nitrate complexes have been synthesized and characterized. The structures of the complexes were confirmed on the basis of elemental analysis, thermal gravimetric analysis, molar conductivity and magnetic moment measurements, FT-IR, mass, and UV-Vis spectroscopy techniques. The complexes show high-thermal stability with >350°C m.p. In all complexes, the ligands are bidentate via one imine nitrogen and a phenolate oxygen. Cu(II) complexes having 1 : 2 M : L ratio are classified as non-electrolytes, whereas 1 : 1 M : L ratio is observed in Fe(III) complexes except [Fe(L₃)₂(H₂O)₂](NO₃) ? 3H₂O. The antimicrobial activities of the ligands and the complexes were evaluated using the disc diffusion method in DMSO as well as minimum inhibitory concentration dilution method against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Proteus mirabilis. Antifungal activities were reported for Candida albicans. The complexes [Fe(L₃)₂(H₂O)₂](NO₃) ? 3H₂O and [Cu(L₃)₂] ? 2H₂O are more effective against S. epidermidis than ciprofloxacin.     

Electrochemical Behavior of Cobalt-Dimethylglyoxime Complex Co(DMG)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript> in the Carbon Dioxide Reduction Process

The electrochemical behavior of a complex of cobalt with dimethylglyoxime Co(DMG)₂(H₂O)₂ is studied by cyclic voltametry. Peaks corresponding to redox transitions Co(III)/Co(II) and Co(II)/Co(I) are observed in the potential region 0.4 to ?1.8 V (Ag/AgCl). The product of reduction of the initial complex interacts with carbon dioxide to form a stable compound, probably an intermediate product of electrocatalytic reduction of CO₂ to CO in the presence of N₄-macrocyclic complexes of cobalt.     

Reverse-phase chromatographic separation of Co(II) and Co(III) as the Co(DEDTC)3 and Co(acac)3 complexes

A reverse-phase chromatographic method is described for the simultaneous determination of Co(II) and Co(III) using gradient elution of the Co(DEDTC)₃ and Co(acac)₃ complexes, respectively, with phosphate buffered acetonitrile water mixtures. The separated Co species are detected spectrophotometrically at 322?nm. The analytical range of the method is 0.1 to 1.25?μg/ml for Co(II) and 0.1 to 1.5?μg/ml for Co(III).     

Synthesis and characterization of new macrocyclic Schiff base derived from 2,6-diaminopyridine and 1,7-bis(2-formylphenyl)-1,4,7-trioxaheptane and its Cu(II), Ni(II), Pb(II), Co(III) and La(III) complexes

A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:16,17-tribenzo-9,12,15-trioxacyclooktadeca-1,5-dien (L) was synthesized by reaction of 2,6-diaminopyridine and 1,7-bis(2-formylphenyl)-1,4,7-trioxaheptane. Then, its Cu(II), Ni(II), Pb(II), Co(III) and La(III) complexes were synthesized by template effect by reaction of 2,6-diaminopyridine and 1,7-bis(2-formylphenyl)-1,4,7-trioxaheptane and Cu(NO₃)₂ · 3H₂O, Ni(NO₃)₂ · 6H₂O, Pb(NO₃)₂, Co(NO₃)₂ · 6H₂O, La(NO₃)₃ · 6H₂O, respectively. The ligand and its metal complexes have been characterized by elemental analysis, IR, ¹H and ¹³C NMR, UV–Vis spectra, magnetic susceptibility, thermal gravimetric analysis, conductivity measurements, mass spectra and cyclic voltammetry. All complexes are diamagnetic and Cu(II) complex is binuclear. The Co(II) was oxidized to Co(III). The comparative electrochemical studies show that the nickel complex exhibited a quasi-reversible one-electron reduction process while copper and cobalt complexes gave irreversible reduction processes in DMSO solution.     

Polysulfonylamine. LXXXIV [1]. Zur Isotypie in den Dimesylamid-Komplexreihen [M(H2O)4{(CH3SO2)2N}2] (MMg,Ca, Ni,Cu, Zn,Cd) und [M(py)4{(CH3SO2)2N}2] (MNi,Cu, Zn,Cd)

Polysulfonylamines. LXXXIV. Isotypic Structures in the Dimesylamide Complex Series [M(H₂O)₄{(CH₃SO₂)₂N}₂] (M?Mg, Ca, Ni, Cu, Zn, Cd) and [M(py)₄{(CH₃SO₂)₂N}₂] (M?Ni, Cu, Zn, Cd) The crystal structures of the trans-octahedral complexes [M(H₂O)₄{(CH₃SO₂)₂N}₂] (M?Ca, Cd), in which the dimesylamide anion acts as a monodentate O-ligand and a tetrafunctional hydrogen bond acceptor, were determined by low-temperature X-ray diffraction. Both belong to an isotypic series (triclinic, space group P1 , Z = 1) that had previously been characterized for M?Mg, Ni, Cu and Zn (Z. Anorg. Allg. Chem. 1996 , 622, 1065). In this structure there exists an extended network of strong hydrogen bonds which is probably the underlying reason why the structure type surprisingly persists across the whole series. To support this explanation by indirect evidence from comparison with suitable structures devoid of strong hydrogen bonding, the analogous trans-octahedral complexes [M(py)₄{(CH₃SO₂)₂N}₂] (M?Mn, Co, Ni, Cu, Zn, Cd) were prepared by treating M[(CH₃SO₂)₂N]₂ with pyridine, and the crystal structures of the Ni, Cu, Zn and Cd compounds were studied by low-temperature X-ray crystallography. As anticipated, the four pyridine complexes do not form an isotypic series but instead two isotypic pairs consisting of the Ni and Zn compounds (monoclinic, space group P2₁/n, Z =2) and of the Cu and Cd complexes (triclinic, space group P1, Z = 1). All molecules of the aqua and the pyridine complexes display crystallographic centrosymmetry. In the hydrates, the mean M? OH₂ and the M? O(anion) distances are 232.6 and 232.7 pm for M ? Ca, 225.5 and 230.3 pm für M ? Cd. The mean M? N and the M? O(anion) bond lengths of the pyridine species amount to 211.8 and 213.1 pm for M ? Ni, 217.0 and 218.5 pm for M ? Zn, 232.8 and 234.4 pm for M ? Cd; the corresponding values for the severely Jahn-Teller distorted Cu complex are 203.6 and 254.5 pm. In the crystals of the pyridine complexes, each methyl group is connected through a weak C? H…?O bond to a sulfonyl oxygen atom of an adjacent molecule.     

Complexation between nickel(II), cobalt(III) and hydrazones derived from pyridoxal 5′-phosphate and hydrazides of 2-,3-,4-pyridinecarboxylic acids in aqueous solution

abstract

The present work reports on stoichiometry, apparent stability constants of biologically relevant complexes of nickel(II), cobalt(III) with hydrazones derived from pyridoxal 5′-phosphate and hydrazides of 2-,3-,4-pyridinecarboxylic acids at pH 7.4, T?=?25.0?°C, I?=?0.25 determined using UV-Vis spectroscopy. The thermodynamic constants of some complexes formation (NiL, NiL₂, NiL₂H) were estimated. Cobalt(II) ion was found to be oxidized to cobalt(III). Co(II) and Co(III) form low-spin state complexes. Hydrazones binding ability (pL_0.5) in the medium mimicking biological ones towards Ni(II) and Co(III) was estimated.