Metallkomplexe mit N2O2S2‐Koordinationssphäre. Synthese und Charakterisierung der Cobalt(II)‐, Nickel(II)‐ und Kupfer(II)‐Komplexe eines 15‐ und eines 16‐gliedrigen N,N′‐bis(2‐hydroxyethyl)‐funktionalisierten makrocyclischen Liganden

Metal Complexes with N₂O₂S₂ Donor Set. Synthesis and Characterization of the Cobalt(II), Nickel(II), and Copper(II) Complexes of a 15‐ and a 16‐Membered Bis(2‐hydroxyethyl) Pendant Macrocyclic Ligand The macrocyclic ligands 6, 10‐bis(2‐hydroxyethyl)‐7, 8, 9, 11, 17, 18‐hexahydro‐dibenzo‐[e, n][1, 4, 8, 12]‐dithiadiaza‐cyclopentadecine ( 1 ) (L¹) and 5, 13‐bis(2‐hydroxyethyl)‐7, 8, 9, 10, 16, 17, 18, 19, 20‐nonahydro‐dibenzo‐[g, o][1, 9, 5, 13]‐dithiadiaza‐cyclohexadecine (L⁴) have been prepared. They form the stable complexes [CoL¹(‐H)CoL¹](ClO₄)₃ ( 2 ), [NiL¹](ClO₄)₂·MeOH ( 3 ), Λ‐[CuL¹](ClO₄)₂·MeOH ( 4a ) and rac‐[CuL¹](ClO₄)₂·MeOH ( 4b ), [NiL⁴](ClO₄)₂ ( 5 ), and [CuL⁴](ClO₄)₂ ( 6 ). The compounds 1 to 6 have been characterized by standard methods and single‐crystal X‐ray diffraction. In the complexes 2 to 6 the metal atoms are octahedrally coordinated by the N₂O₂S₂ donor set of the ligands. L¹ and L⁴ are folded herein along the N···M···S‐ and the N···M···N′‐axes, respectively. This results at the metal atom in a all‐cis‐configuration for the complexes of L¹ and a trans‐N₂‐cis‐O₂‐cis‐S₂‐configuration for the complexes of L⁴. The cobalt(II) complex 2 is a dimer, bridged by a rather short hydrogen bridge of 2.402(12)Å length. The copper(II) complexes of L¹ and L⁴ differ with respect to the Jahn‐Teller‐distortion.     

Catalyzed Autoxidation of Hydrogensulfite by Cobalt(II) (2,3,9,10-tetramethyl-1,4,8,11-tetraaza-cyclotetradeca-1,3,8,10-tetraene) (H 2 O) 2 2+

The catalytic autoxidation of hydrogensulfite (hydrogentrioxosulfate(1-)) in the presence of Co(tim)(H 2 O) 2 2+ (tim=2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) was studied. Dioxygen reacts with excess sulfite in the presence of Co(tim)(H 2 O) 2 2+ in a complex process (a minimum of five kinetic steps can be identified) to produce Co(tim)(SO 3 ) x (3 m 2 x )+ ( x =1 or 2) ( u max at 350 nm) and sulfate. Seventy turnovers over 4 h were attained in a system where dioxygen and sulfite were supplied constantly. The Co(III) product formed reacts only slowly with dioxygen to produce sulfate. A mechanistic analysis of the results implies the involvement of a Co(tim)-dioxygen adduct, stabilized by an axial sulfite ligand.     

Copper(II), Cobalt(II), and Nickel(II) Complexes of two Novel Pyridine‐derived Macrocyclic Ligands bearing o‐ and pNitrobenzyl Pendant Groups

The pendant‐armed ligands L¹ and L² were synthesized by N‐alkylation of the four secondary amine groups of the macrocyclic precursor L using o‐nitrobenzylbromide (L¹) and p‐nitrobenzylbromide (L²). Nitrates and perchlorates of Cu^II, Ni^II and Co^II were used to synthesize the metal complexes of both ligands and the complexes were characterized by microanalysis, MS‐FAB, conductivity measurements, IR and UV‐Vis spectroscopy and magnetic studies. The crystal structures of L¹, [CuL¹](ClO₄)₂·CH₃CN·H₂O, [CuL²](ClO₄)₂·6CH₃CN, [CuL²][Cu(NO₃)₄]·5CH₃CN·0.5CH₃OH and [NiL²](ClO₄)₂·3CH₃CN·H₂O were determined by single crystal X‐ray crystallography. These structural analysis reveal the free ligand L¹, three mononuclear endomacrocyclic complexes {[CuL¹](ClO₄)₂·CH₃CN·H₂O, [CuL²](ClO₄)₂·6CH₃CN and [NiL²](ClO₄)₂·3CH₃CN·H₂O} and one binuclear complex {[CuL²][Cu(NO₃)₄]·5CH₃CN·0.5CH₃OH} in which one of the metals is in the macrocyclic framework and the other metal is outside the ligand cavity and coordinated to four nitrate ions.     

Kinetics and mechanism of the copper(II) catalyzed oxidation of N-substituted p-phenylenediamines by 2,3,9,10-tetramethyl-1,4,5,7,8,11,12,14-octaazacyclotetradeca-1,3,8,10-tetraenecopper(II)

The kinetics of oxidation of N,N-dimethyl- and N,N,N,N-tetramethyl-p-phenylenediamines, to the corresponding semiquinonediimine radical and the quinonediimine, with a macrocyclic copper(II)-complex were studied at pH7. Under pseudo-first order conditions, the reaction rate for the N,N,N,N-tetramethyl derivative was much faster than for N,N-dimethyl-p-phenylenediamine, due to the increased probability of electron transfer. The reaction rate decreases with increasing acidity of the medium as a result of protonation of the amine nitrogen atoms. The rate constants and activation parameters were evaluated and the reaction was found to be enthalpy controlled. Furthermore, kinetic measurements revealed a remarkable superadditive effect when CuCl₂ solution was added, even at concentrations lower than that of the copper complex. This observation was used for the kinetic determination of copper ions at concentrations <10^–5M.     

Binuclear Co(II), Ni(II), Cu(II) and Zn(II) complexes with Schiff-bases derived from crown ether platforms: Rare examples of ether oxygen atoms bridging metal centers

Bibracchial lariat ethers L³ and L⁴, derived from the condensation of N,N′-bis(2-aminobenzyl)-1,10-diaza-15-crown-5 or N,N′-bis(2-aminobenzyl)-4,13-diaza-18-crown-6 with salicylaldehyde, form binuclear complexes with Co(II), Ni(II), Cu(II) and Zn(II). Our studies show that the different denticity and crown moiety size of the two related receptors give rise to important differences on the structures of the corresponding complexes. Single crystal X-ray diffraction analysis shows that the [Ni₂(L³)(H₂O)₂]²⁺ and [Cu₂(L³)(NO₃)]⁺ complexes constitute a rare example in which an oxygen atom of the crown moiety is bridging the two six coordinate metal ions. In contrast, none of the oxygen atoms of the crown moiety is acting as a bridging donor atom in the [Co₂(L⁴)(CH₃CN)₂]²⁺, [Cu₂(L⁴)]²⁺ and [Zn₂(L⁴)]²⁺ complexes. This is attributed to the larger size the crown moiety and the higher denticity of L⁴ compared to L³. In [Co₂(L⁴)(CH₃CN)₂]²⁺ the metal ions show a distorted octahedral coordination, while in the Cu(II) and Zn(II) analogues the metal ions are five-coordinated in a distorted trigonal bipyramidal environment. In [Cu₂(L³)(NO₃)]⁺ the coordinated nitrate anion acts as a bidentate bridging ligand, which results in the formation of a 1D coordination polymer.     

Cobalt(II) Complexes with Dicyanamide — from Binuclear Entities to Chains

One binuclear complex [Co(bpm*)₂(dca)]₂(ClO₄)₂ ( 1 ) and two 1D chain Co^II complexes, {[Co(bpm)₂(dca)](ClO₄)}_n ( 2 ) and [Co(dmf)₂(dca)₂]_n ( 3 ), (bpm*: bis[(3, 5‐dimethyl)pyrazolyl]methane; bpm: bis(pyrazolyl)methane; dca: dicyanamide; dmf: N, N‐dimethyl formamide) have been prepared and structurally characterized. The cobalt atoms are hexa‐coordinated forming a slightly distorted octahedral coordination. Compound 1 crystallizes in the monoclinic system, space group P2₁/c, a = 9.849(3)Å, b = 21.944(7)Å, c = 13.814(5)Å, β = 94.824(6), Z = 4, R₁ = 0.0672, wR₂ = 0.1395. 1 is a binuclear complex linked by two dca ligands, and each Co^II ion is coordinated by two terminal bpm* ligands. Compound 2 crystallizes in the orthorhombic system, space group Cmcm, a = 10.377(4)Å, b = 13.594(5)Å, c = 15.999(6)Å, Z = 4, R₁ = 0.0609, wR₂ = 0.1328. The structure of 2 can be described as a one‐dimensional zigzag chain of Co^II ions bridged by one dca ligand. Each Co^II ion in the chain is coordinated by two bpm ligands. Compound 3 crystallizes in the monoclinic system, space group C₂, a = 13.559(15)Å, b = 7.393(8)Å, c = 8.110(9)Å, β = 112.228(15), Z = 2, R₁ = 0.0260, wR₂ = 0.0760. 3 has a one‐dimensional linear chain of Co^II ions bridged by two dca ligands, in which each Co^II ion is coordinated with two dmf molecules.     

The supramolecular chemistry of metal complexes with heavily substituted imidazoles as ligands: Cobalt(II) and zinc(II) complexes of 1-methyl-4,5-diphenylimidazole

An investigation of the M^II/X⁻/L [M^II = Co, Ni, Cu, Zn; X⁻ = Cl⁻, Br⁻, I⁻, NCS⁻, NO₃⁻, N₃⁻, CH₃COO⁻; L = 1-methyl-4,5-diphenylimidazole] general reaction system towards the detailed study of the intermolecular interactions utilized for controlling the supramolecular organization and the structural consequences on the structures produced has been initiated. Three representative complexes with the formulae [Co(NO₃)₂(L)₂] (1), [Zn(NO₃)₂(L)₂] (2) and [Co(NCS)₂(L)₂]·EtOH (3·EtOH) have been synthesized and characterized by spectroscopic methods and single-crystal X-ray analysis. Compounds 1 and 2 are isomorphous (tetragonal, I4₁cd) with their metal ions in a severely distorted octahedral Co/ZnN₂O₄ environment, while 3·EtOH crystallizes in P2₁/c with a tetrahedral CoN₄ coordination. The structural analysis of 1, 2 and 3·EtOH reveals a common mode of packing among neighbouring ligands (expressed through intramolecular π–π interactions between the 4,5-diphenylimidazole moieties), enhancing thus the rigidity and stability of the complexes. The bent coordination of the two isothiocyanates in 3 [Co–NCS angles of 173.8(2) and 160.8(2)°] seems to be caused by intermolecular hydrogen bonding and crystal packing effects.     

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.     

Heterodinukleare Cobalt(II)‐, Nickel(II)‐, Kupfer(II)‐, Zink(II)und Palladium(II)‐Komplexe mit einem makrocyclischen Liganden vom Schiff‐Basen‐Typ: Synthesen und Strukturen

Complexes with Macrocyclic Ligands. IV. Heterodinuclear Cobalt(II), Nickel(II), Copper(II), Zinc(II) and Palladium(II) Complexes with a Macrocyclic Ligand of Schiff‐Base Type: Syntheses and Structures The synthesis and properties of nickel(II), copper(II), and palladium(II) complexes, [ML^Ph] ( 3 ; L^Ph = N,N′‐phenylene‐bis(3‐formyl‐5‐tert.‐butyl‐salicylaldimine)), are described. These neutral mononuclear complexes react with metal(II) perchlorate and 1,3‐propylenediamine to form heterodinuclear, macrocyclic, cationic complexes of the type [MM′(L^Ph,3)]²⁺ ( 4 ; M = Ni, Cu, Pd; M′ = Co, Cu, Zn). The structures of the five new compounds [NiCo(L^Ph,3)](ClO₄)₂, [NiCu(L^Ph,3)](ClO₄)₂, [CuCu(L^Ph,3)](ClO₄)₂, [CuZn(L^Ph,3)](ClO₄)₂, and [PdCu(L^Ph,3)](ClO₄)₂ were determined by X‐ray diffraction.     

Monomere und polymere Dimethylaminothioquadratato‐Komplexe: Die Kristallstrukturen von Nickel(II)‐, Cobalt(II)‐, Silber(I)‐, Platin(II)‐, Gold(I)‐, Quecksilber(II)‐ und Blei(II)‐Dimethylaminothioquadrataten

Monomeric and Polymeric Dimethylaminothiosquarato Complexes: The Crystal Structures of Nickel(II), Cobalt(II), Silver(I), Platinum(II), Gold(I), Mercury(II) and Lead(II) Dimethylaminothiosquarates The ligand 2‐dimethylamino‐3, 4‐dioxo‐cyclobut‐1‐en‐thiolate, Me₂N‐C₄O₂S⁻ (L) forms neutral and anionic complexes with nickel(II), cobalt(II)‐, silver(I)‐, platinum(II)‐, gold(I)‐, mercury(II)‐ and lead(II). According to the crystal structures of seven complexes the ligand is O, S‐chelating in [Ni(L)₂(H₂O)₂]·2 H₂O, [Co(L)₂(CH₃OH)₂] and (with limitations) in [Pb(L)₂·DMF]. In the remaining compounds the ligand behaves essentially as a thiolate ligand. The platinum, gold and mercury complexes [TMA]₂[Pt(L)₄], [TMA] [Au(L)₂] and [Hg(L)₂] are monomeric. In [TMA][Ag₂(L)₃]·5.5 H₂O a chain‐like structure was found. In the asymmetric unit of this structure eight silver ions, with mutual distances in the range 2.8949(4) to 3.1660(3)Å, are coordinated by twelve thiosquarato ligands. [Pb(L)₂·DMF] has also a polymeric structure. It contains a core of edge‐bridged, irregular PbS₄ polyhedra. TMA[Au(H₂NC₄O₂S)₂] has also been prepared and its structure elucidated.     

Syntheses and Structural Characterization of Two Nitrilotriacetate Cobalt Complexes: [{CoK2(NTA)(Hmta)(H2O)3}NO3]n and [{Co(4,4′‐bpy)2(H2O)4}{Co2(NTA)2(4,4′‐bpy)(H2O)2}]

Two nitrilotriacetate cobalt complexes {[CoK₂(NTA)(Hmta)(H₂O)₃]NO₃}_n ( 1 ) and [{Co(4,4′‐bpy)₂(H₂O)₄}{Co₂(NTA)₂(4,4′‐bpy)(H₂O)₂}] ( 2 ) (NTA = nitrilotriacetate anion, Hmta = hexamethylenetetramine and 4,4′‐bpy = 4,4′‐bipyridine) were prepared and characterized by IR, elemental analysis and single crystal X‐ray diffraction study. The influence of the neutral ancillary ligands on the formation of the complexes with different structures in the Co‐NTA system was discussed. The coordination of NTA and Hmta to Co²⁺ ions only resulted in the formation of mononuclear [Co(NTA)(Hmta)]^? ions which are further connected by K⁺ ions and water molecules to form a three‐dimensional network. The use of 4,4′‐bpy as ancillary ligand in 2 led to the formation of separate mononuclear [Co(4,4′‐bpy)₂(H₂O)₄]²⁺ and dinuclear [Co₂(NTA)₂(4,4′‐bpy)(H₂O)₂]^2? which are further connected by hydrogen bonds to form a supramolecular three‐dimensional network. In these cases it seems to suggest that the addition of neutral ancillary ligand into the Co‐NTA system leads to the formation of lower dimensional structures when the contribution of alkali ions to the structural dimensionality is neglected.     

Co(II), Ni(II) and Cu(II) metal complexes with a N8 azamacrocyclic ligand

Hydrated nitrate and perchlorate salts of the transitional metal ions Co²⁺, Ni²⁺ and Cu²⁺ have been used to investigate the coordination capability of the octaaza macrocycle L derived from 2,6-diformylpyridine and diethylenetriamine. The synthesis of the metal complexes was carried out in 1:1 and 2:1 metal:ligand molar ratios, but dinuclear complexes were obtained in all cases due to the size of the 24-membered ligand. The complexes have been characterized by elemental analysis, molar conductivity, mass spectrometry, IR spectroscopy, diffuse reflectance and magnetic measurements. The dinuclear nature of the compounds was confirmed by X-ray diffraction. The crystal structures of [Ni₂L(NO₃)₂](NO₃)₂, [Cu₂L(NO₃)₄] and [Cu₂L(ClO₄)₄], were determined.     

Syntheses,Structures, and Magnetic Properties of Two Novel Cobalt(II) Coordination Polymers Constructed from Pyridine‐2,6‐dicarboxylic Acid N‐oxide (PDCO)

Two new cobalt(II) coordination polymers, [Co(PDCO)(H₂O)₂]_n ( 1 ) and [Co(PDCO)(bix)(2H₂O)₂·H₂O]_n ( 2 ) ( PDCO= pyridine‐2,6‐dicarboxylic acid N‐oxide, bix = 1,4‐bis(imidazol‐1‐ylmethyl)‐benzene) have been synthesized under hydrothermal conditions. Single‐crystal X‐ray analyses show that compound 1 is a 1D helical chainlike structure with 4₁ screw axes parallel to the crystallographic c‐axis and interchain hydrogen‐bonding interactions further result in a 3D framework; for compound 2 , each bix ligand connects two Co1 atoms (or two Co2 atoms) to give a zigzag chain structure and these 1D chains are connected by offset face‐to‐face π···π and hydrogen bond interactions to generate a 3D architecture. The thermogravimetric analyses were investigated for 1 and 2 . The determination of variable temperature magnetic susceptibilities indicates an antiferromagnetic interaction between the metal atoms for 1 and 2 .     

Hydrothermal synthesis and structure of one-dimensional Co(dien)2(VO3)3·(H2O) (dien=diethylenetriamine)

One-dimensional Co(dien)₂(VO₃)₃·(H₂O) was prepared from the hydrothermal reaction of NH₄VO₃, Co₂O₃, diethylenetriamine (dien) and H₂O at 130 °C. The compound crystallizes in the monoclinic system, space group P2₁/c with a=16.1581(6) Å, b=8.7006(3) Å, c=13.9893(4) Å, β=103.1483(11)°, V=1915.13(11) Å³, Z=4, and R₁=0.0268 for 3060 observed reflections. Single crystal X-ray diffraction revealed that the structure is composed of infinite one-dimensional chains formed by corner-sharing VO₄ tetrahedra with Co(dien)³⁺ complex cations and crystallization water molecules occupying the interchain positions, which are held together to a three-dimensional network via extensive hydrogen-bonding interactions. The compound, with a new zig-zag conformation of metavanadate chains, is the first example of vanadium oxides incorporating trivalent transition metal coordination groups. Other characterizations by elemental analysis, IR and thermal analysis are also described.     

Synthese und Charakterisierung von Cobalt(II)‐ und Kupfer(I)‐Komplexen mit Guanidin‐Pyridin‐Hybridliganden

Syntheses and Structures of Cobalt(II) and Copper(I) Complexes with Guanidine‐Pyridine Hybridligands The guanidine‐pyridine hybridligands N‐(1,3‐dimethylimidazolidin‐2‐ylidene)‐2‐(pyridine‐2‐yl)ethanamine (DMEGepy, L1 ) and 1,1,3,3‐tetramethyl‐2‐(2‐(pyridine‐2‐yl)ethyl)guanidine (TMGepy, L2 ) have been synthesized and characterized. The reaction of DMEGepy with CoCl₂ and TMGepy with CuI lead to the mononuclear complexes {N‐(1,3‐dimethylimidazolidin‐2‐ylidene)‐2‐(pyridine‐2‐yl)ethanamine}cobalt(II) dichloride ( 1 ) and {1,1,3,3‐tetramethyl‐2‐(2‐(pyridine‐2‐yl)ethyl)guanidine}copper(I) iodide ( 2 ). By the characterization of these complexes we are able to compare the complexation chemistry of the hybridguanidine and bisguanidine ligands with regard to the various N donor functions systematically.     

Cobalt complexes of terpyridine ligands: Crystal structure and nuclease activity

Cobalt(II) (1) and cobalt(III) (2) complexes of tridentate ligand, imidazole terpyridine (Itpy), have been synthesized and characterized by both spectroscopic and electrochemical techniques. Single crystal X-ray diffraction studies of complexes 1 and 2 shows that the complexes belong to monoclinic crystal system, with the two Itpy ligands coordinated to the central metal ion. The binding behavior of both the cobalt complexes to calf thymus DNA has been investigated by UV–Vis, fluorescence spectroscopy, viscosity and electrochemical measurements. The results suggest that complexes 1 and 2 bind to DNA through intercalation. The intrinsic DNA binding constant values obtained from absorption spectral titration studies were found to be (5.07 ± 0.12) × 10³ M⁻¹ and (7.46 ± 0.16) × 10³ M⁻¹, respectively, for complexes 1 and 2. Gel electrophoresis studies with the cobalt complexes show that while complex 1 cleaves DNA in the presence of hydrogen peroxide, complex 2 cleaves DNA in the presence of ascorbic acid and hydrogen peroxide.     

Complexes of N‐Thiophosphorylthiourea tBuNHC(S)NHP(S)(OiPr)2 with Zinc(II), Cadmium(II), Nickel(II), and Cobalt(II) Cations

Reaction of the potassium salt of N‐thiophosphorylthiourea tBuNHC(S)NHP(S)(OiPr)₂ ( HL ) with Zn^II, Cd^II, Ni^II and Co^II in aqueous EtOH leads to complexes of common formula M(L‐S,S′)₂ ( ML₂ ). Complexes were investigated by IR, UV‐Vis, ¹H and ³¹P{¹H} NMR spectroscopy and microanalysis The structure of complex NiL₂ was investigated by single crystal X‐ray diffraction analysis. The nickel(II) ion has a squre‐planar environment, S₄, with two anionic ligands involving 1,5‐S,S′‐coordination mode. The ligands are bound in a trans configuration.     

Cobalt(II), nickel(II), and zinc(II) complexes with bidentate N,N′-bis(β-phenylcinnamaldehyde)-1,2-diiminoethane Schiff base: synthesis and structures

A series of complexes of the type M(Phca₂en)X₂, where Phca₂en=N,N′-bis(β-phenyl-cinnamaldehyde)-1,2-diiminoethane, M(II)=Co, Ni or Zn and X=Cl, Br, I or NCS have been synthesized and characterized. The crystal and molecular structures of Co(Phca₂en)Cl₂ (2), Ni(Phca₂en)Br₂ (5) and Zn(Phca₂en)Cl₂ (6) were determined by X-ray crystallography from single-crystal data. Complexes 2 and 5 are isomorph and isostructure, in which the coordination polyhedron about the central metal ion is distorted tetrahedron with Cl---Co---Cl, 110.17(6)°; N---Co---N, 84.16(13)° and Cl---Zn---Cl, 112.02(6)°; N---Zn---N, 83.45(16)°. The complex 5 crystallizes in triclinic system with two molecules per asymmetric unit, both having nickel ion in distorted tetrahedral geometry, Br---Ni---Br, 122.645(18)° and 125.729(18)°; N---Ni---N, 84.63(9)° and 85.08(9)°. These structures consist of intermolecular hydrogen bonds of the type C---HX. The formation of the C---HM weak intramolecular hydrogen bonds due to the trapping of C---H bonds in the vicinity of the metal atoms are reported for 2, 5 and 6. A ¹H NMR study of Zn complexes gives further evidence for the presence of such interactions and their significance. The spectral properties of the above complexes are also discussed.     

Partial and Gradual Hydrolysis of 2,2′-Biimidazoline upon Coordination to Metal Ions,yielding New Chelating Ligands - Synthesis,Characterization and X-ray Structure of two Examples with Cobalt(III) and Copper(II)

The synthesis, a full structural characterization of two transition-metal compounds obtained by in-situ hydrolysis and partly hydrolysis of the ligand 2, 2′-biimidazoline (abbreviated as biz) is reported. When the biz ligand is completely hydrolysed the compound, N, N′-bis(2-aminoethyl)oxamide (abbreviated as H₂oxen) is obtained, while the partial hydrolysis results in the ligand N-(2-aminoethyl)imidazoline-2-carboxamide (abbreviated as Hoxim). The Co^III ion in the mononuclear Co^III compound, [Co(biz)(oxim)(NCS)](ClO₄)(C₂H₅OH)_1/6(H₂O)_1/6 ( 1 ), has an octahedral coordination consisting of 6 nitrogen atoms with a distance varying from 1.889(6) to 1.950(5) Å. Two nitrogen atoms originating from a biz molecule, 3 nitrogen atoms are from the oxim ligand and one nitrogen is from the thiocyanate anion. Each Cu^II ion in the dinuclear Cu^II compound, [Cu₂(H₂oxen)(oxim)₂(C₂H₅OH)₂] (ClO₄)₂ ( 2 ), has a slightly distorted square-pyramidal structure of which the basal plain consists of3 nitrogen atoms of the oxim ligand and one nitrogen atom of the H₂oxen ligand, which is used as a “spacer” connecting the second Cu^II atom, with Cu-N distances which vary from 1.944(2) to 2.037(2) Å. The apical position is formed by the oxygen atom of a semi-coordinating ethanol molecule with a Cu-O distance of 2.446(2) Å. The compounds are characterized by elemental analysis, ligand field, infrared and, for the Cu^II ion, also by EPR spectroscopy.     

Syntheses and crystal structures of two 2D coordination polymers of cobalt(II) and nickel(II) with the Malonate Dianion Ligand

Two 2D complexes, [Co(mal)(phen)(H₂O)₂] (1) and [Ni(mal)(phen)(H₂O)₂] (2) (mal?=?malonate dianion; phen?=?1,10-phenanthroline), have been synthesized by the reaction of Co(ClO₄)₂·6H₂O and Ni(ClO₄)₂·6H₂O with disodium malonate and 1,10-phenanthroline in MeOH/H₂O solution. Their crystal structures have been determined by X-ray diffraction. The structures of Complexes 1 and 2 show that each metal ion is coordinated by one 1,10-phenanthroline, two water molecules and a malonate ligand forming a distorted octahedral environment and each mononuclear fragment forms a 2D supramolecular network through H-bonding interactions.