Metal-(phenylthio)alkanoic acid interactions— VII. The crystal and molecular structures of diaquabis[(benzylthio)acetato]-zinc(II), catena- [diaqua-tetra[(benzylthio)acetato]-bis[cadmium(II)], catena-tetra-μ-{2-methyl-3- (phenylthio)propionato-O,O′]-bis[copper(II)]} and tetra-μ-[2-methyl-2-(phenylthio)propionato-O,O′]- bis[ethanolcopper(II)]

The crystal structures of diaquabis[(benzylthio)acetato]zinc(II), [Zn(BTA)₂ (H₂O)₂] (1), catena-[diaqua-tetra[(benzylthio)acetato)]-bis[cadmium(II)], [Cd₂(BTA)₄ H₂O)₂]_n (2), catena-{tetra-μ-[2-methyl-3-(phenylthio)propionato-O,O′]-bis[copper (II)]}, [Cu₂(MPTP)₄]_n (3) and tetra-μ-[2-methyl-2-(phenylthio)propionato-O,O′]- bis[ethanol copper(II)], [Cu₂(PTIBA)₄(EtOH)₂] (4) have been determined using X-ray diffraction techniques. Complex (1) is monomeric with distorted octahedral stereochemistry and lies on a two-fold rotational axis. The MO₆ coordination involves four oxygens from two slightly asymmetric bidentate BTA car☐yl groups [ZnO, 2.138(3), 2.28(3)Å] and two cis-related waters [ZnOw, 1.996(3)Å]. The cadmium complex (2) is best described in terms of a polymer with the repeating unit consisting of two different centres, one seven, the other six-coordinate. With the first, the distorted MO₆S coordination sphere has four oxygens from two asymmetric bidentate car☐ylate groups (ligands B and C) [CdO, 2.36, 2.56(1)Å; 2.26, 2.67(1)Å], an oxygen and a sulphur from a bidentate chelate ligand (A) [CdO, 2.36(1)Å; CdS, 2.773(4)Å] and an oxygen from a bridging car☐yl group (ligand D) [CdO, 2.28(1)Å]. Ligands C and D also bridge two Cd centres through sulphurs [CdS, 2.739, 2.723(4)Å]. The second car☐yl oxygen of ligand A also forms a bridge to the second Cd [(CdO, 2.30(1)Å], while the distorted octahedral MO₄S₂ stereochemistry is completed by two waters [CdO, 2.25(1), 2.49(1)Å] and a sulphur from ligand D [CdS, 2.723(4)Å] giving a polymer structure. Complexes (3) and (4) are centrosymmetric tetra-car☐ylate bridged dimers [for (3) Cu ··· Cu, 2.586(3)Å; mean CuO(equatorial), 1.957(11)Å; for the two independent dimers in (4), Cu ··· Cu, 2.596(1), 2.616(1)Å; CuO (equatorial), 1.952(4), 1.968(4)Åmean]. The axial positions of the dimer in (3) are occupied by car☐yl oxygens of adjacent dimers [CuO, 2.280(9)Å] forming a polymer structure. In contrast, these positions in (4) are occupied by ethanol molecules with CuO, 2.222(3) and 2.177(4)Årespectively for the two independent dimers.     

Synthesis and Structure of bis(μ-2-aminopyridine N-oxide)-bis[dichlorocopper(II)]

1 INTRODUCTIONMany complexes of 2-aminopyridine N-oxide (apo) have been characterized by infrared spectra, X-ray powder diffraction spectra, and by magnetic measurements and electronic spectra at liquid nitrogen temperature, but very few of them are their crystal X-ray studies[1~3]. Recently, a number of bridged binuclear copper (II) complexes have been reported, some of which have important potential applications in bioinorganic chemistry and materials[4~6]. Particularly, the complexes …     

Two 2-D copper(II) azido compounds: catena -poly[ di -μ1,1- azido,di -μN,O-(quinolinecarboxylato)(aqua)copper(II)] and 1-D catena -poly[ di -μN,N′-(quinoxaline)copper(II)nitrate]

We synthesized three copper(II) complexes with two structurally related polydentate ligands, quinoline-4-carboxylic acid (quCOOH) and quinoxaline (qux). The structures of these complexes were determined using X-ray single crystal crystallography. Complex 1, [Cu(quCOO)(N₃)(H₂O)] _n , has a 2-D polymeric structure through di-μ_1,1 azido groups forming (Cu₂N₂) dimeric units and di-μ_N,O quinoline carboxylate bridging the binuclear copper units. [Cu(quCOO)(N₃)(H₂O)] _n · 0.87MeOH, (2), has the same structure as 1 in addition to MeOH molecules separating the 2-D sheets of [Cu(quCOO)(N₃)(H₂O)] _n . [Cu(qux)(NO₃)₂] _n , (3), has no coordinated azido groups, but the quinoxaline is a bidentate bridging ligand giving a 1-D chain, while the μ_O,O′ chelating nitrato groups stabilize the chain structure by forming a square planar coordination sphere around copper. IR and UV–Vis spectra of the complexes are in agreement with the crystal structures.     

Synthesis and catalytic activity of DI-μ-methoxo-bis[(2-aminopyridine)(chloro)copper(II)] and m-xylylenediamine Zn(OAc)2

Compound I, [di-μ-methoxo-bis[(2-aminopyridine)(chloro)copper(II)], was obtained by two different synthetic routes. In synthetic route 1, we first obtained intermediate by the addition of two equivalents of o-aminopyridine to copper chloride in an ethanolic solution, and then we recrystallized the intermediate from methanol and n-hexane to give compound I. Synthetic route 2 involved the reaction of o-aminopyridine with copper chloride in a methanol solution directly. The crystal structure of compound I was obtained. The reaction of m-xylylenediamine with Zn(OAc)₂ · 2H₂O in THF resulted in the production of one novel zinc complex C₁₂H₁₈N₂O₄Zn, bis(m-xylenediamine)zinc (II) and its structure was determined by X-ray diffraction analysis. Complexes I and II were also characterized by elemental analysis, and IR. Then they were applied as catalysts for the Henry reaction, and they achieved good conversions (64 and > 99%, respectively).     

Crystal structure and magnetic properties of catena-μ-(pyrazine-N,N′)bis[(p-nitrobenzoyl)trifluoroacetonato-O,O′]copper(II)

The X-ray crystal structure, variable-temperature magnetic susceptibilities and e.s.r. spectra are reported for the title complex. The complex crystallises as infinite chains in which the copper(II)-β-diketonate units are bridged axially by ambidentate pyrazine ligands with a Cu⋯Cu separation of 7.6700(2) Å. The magnetic susceptibility measurements in the range 5–325 K are consistent with the ferromagnetic intrachain exchange. The S=1/2 Heisenberg ferromagnetic linear chain analysis results in magnetic parameters of g=2.12 and J/k=0.6 K.     

Synthesis,spectroscopy, magnetism and X-ray structure of μ-(bipyrimidine)-bis[aqua(bipyrimidine)(saccharinato)copper(II)] bis(saccharinate) tetrahydrate

The compound [Cu₂(bipym)₃(sac)₂(H₂O)₂](sac)₂(H₂O)₄ (bipym = 2,2-bipyrimidine and sac = saccharin) crystallizes in the space group P-1, with a = 10.710(3), b = 10.725(3), c = 13.637(5) Å, a = 70.07(3), = 80.31(2), g = 82.87(3)° and Z = 2. The geometry in the centrosymmetric dinuclear complex around each Cu^II ion is a distorted octahedron, in which the equatorial plane is formed by a nitrogen atom of a bis-didentate bridging bipym ligand, two nitrogen atoms of a didentate bipym ligand, and the nitrogen atom of a coordinating sac ligand. The axial positions in the octahedron are occupied by a second nitrogen of the bis-didentate bridging bipym ligand and a water molecule. The lattice contains two saccharinate anions and four water molecules held together in a hydrogen-bonded network. The i.r vibrations of the bipym ligand are found as a quasi-symmetric doublet at 1558 and 1580 cm^–1, while the most important i.r vibrations of the sac ligand are observed at 1629 and 1644 cm^–1 (carbonyl vibrations) and at 1285 and 1159 cm^–1 (sulfonyl vibrations). The magnetic exchange interactions between the Cu ions is very weak and is ferromagnetic (J < 0.1 cm^–1).     

Square-planar copper(II) complexes with a novel tetradentate amido-carboxylate ligand. Crystal structure of [Co(H2O)6][Cu(mda)] · 2H2O

A novel O—N—N—O-type tetradentate ligand H₄mda (H₄mda = malamido-N,N-diacetic acid) and the corresponding square-planar copper(II) complexes have been prepared and characterized. The mda^4– ligand coordinates to the copper(II) ion via two pairs of deprotonated ligating atoms (two carboxylate oxygens and two deprotonated amide nitrogens) with in-plane square chelation. A four-coordinate, square-planar geometry has been established crystallographically for the [Co(H₂O)₆][Cu(mda)] · 2H₂O complex. Structural data correlating the square-planar geometry of the [Cu(mda)]^2– unit are discussed in relation to information obtained for similar complexes. The i.r., electronic, absorption and reflectance spectra of the complexes are analysed in comparison with related complexes of known geometries.     

Synthesis,structure and magnetic studies of copper(II)-nickel(II) complexes withN,N′-bis(2-aminopropyl)oxamidocopper(II)

Three novel heterobinuclear complexes have been prepared and identified as [Cu(oxap)Ni(L)₂](ClO₄)₂·ξH₂O, where oxap denotes theN,N′-bis(2-aminopropyl)oxamido dianion and L denotes 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen) or 5-nitro-1,10-phenanthroline (NO₂-phen). The crystal structure of [Cu(oxap)Ni(phen)₂]-(ClO₄)₂·2H₂O has been determined. Crystal data: triclinic, space group , a=12.079 (6), b=12.409 (4), c=17.261 (8) ?, α=70.91 (2), β=86.72 (4), γ=89.19 (3)^o. At room temperature, Z=2. The Cu^II is in a square planar environment and the Ni^II is in an octahedral environment. The Cu−Ni distance is 5.292 ?. The temperature dependences of the magnetic susceptibilities of [Cu(oxap)Ni(phen)₂]-(ClO₄)₂·2H₂O and [Cu(oxap)Ni(bipy)₂](ClO₄)₂ have been studied in the 4.2–300 K range, giving the exchange integral J=−92.4 cm⁻¹ for bipy and J=−94.3 cm⁻¹ for phen. These results are commensurate with antiferromagnetic interactions between the adjacent metal ions.     

Synthesis and Characterization of Nitrato-Triamine-Metal(II) Complexes. Conglomerate Crystallization Part 55. Crystal Structure of [Ni(dien)(O2NO)(ONO2)] (I), {[Cu(dien)-(μ-ONO2)]NO3}∞ (II), [Zn(dien)(O2NO)(ONO2)] (III), [Ni(Medpt)(O2NO)(ONO2)] (IV) and [Cu(Medpt)(ONO2)2] (V)

In absolute ethanol and in the presence of triethylorthoformate, reactions of metal(II) nitrates with linear tridentate amines afforded metal complexes of the formula M(NNN)(NO₃)₂, where M = Ni²⁺, Cu²⁺ and Zn²⁺, and NNN = dien and Medpt. The compounds fall into three categories in accordance with their stereochemistry and mode of binding of the nitrato ligands. Compounds I, [Ni(dien)(O₂NO)(ONO₂)] and III, [Zn(dien)(O₂NO)(ONO₂)] are isomorphous and isostructural. They crystallize in the monoclinic space group P2₁/n with nearly identical cell constants. The stereochemistry of these two compounds is such that the terdentate dien ligand forms a fac MN₃ moiety with the two oxygens of the bidentate nitrato ligand trans to the terminal NH₂. These ligands form the base of the octahedral arrangement in which the sixth position, trans to the secondary nitrogen of the dien, is an oxygen of the monodentate nitrato ligand. Compound IV, [Ni(Medpt)(O₂NO)(ONO₂)] falls into the same category as I and III despite the fact that the two rings in the Ni-Medpt moiety are six-membered rings, unlike those in compounds I and III which are five-membered rings. Nevertheless, the nickel-amine arrangement is fac. The bidentate nitrato-oxygens are trans to the terminal NH₂ of the amine ligand, and the oxygen of the monodentate nitrato ligand is trans to the tertiary amine-nitrogen. Such stereochemistry is prevalent for nickel and zinc compounds. Interestingly, compound IV crystallizes as a conglomerate (space group P2₁2₁2₁). Compound II, {[Cu(dien)(μ-ONO₂)]NO₃}_∞ belongs to the second category and has a polymeric structure. The repeating fragment in the polymeric chain is a Cu(dien)-O fragment with the monodentate nitrato ligand occupying an equatorial position of the base. A second oxygen of the equatorial nitrate becomes an axial ligand for an adjacent Cu-N₃O fragment. In this way the substance propagates into an infinite chain. The repeating unit has an effective square pyramidal, five-coordinate, configuration. Finally, the compound crystallizes as a racemate. The second nitrate necessary for charge compensation of this copper(II) compound is ionic and its function is to hold the infinite chains of the lattice. The third category represented by compound V, [Cu(Medpt)(ONO₂)₂] contains two molecules in the asymmetric unit of the racemic lattice (monoclinic, space group P2₁/a). The structure of Cu-Medpt is unlike that of IV in that both species present in the asymmetric unit have the amine ligand in a mer configuration which together with a monodentate oxygen of a nitrato ligand form a base plane of a square pyramid. The fifth ligand of both Cu²⁺ ions is a second monodentate nitrato ligand. The stereochemical differences between the two Cu²⁺ ions are insignificant for the Cu-Medpt fragment, which share the same conformation and configuration. The major difference between the two species is the torsional angles defined by the Cu-O-N-O angles. The difference arises from variation in the hydrogens of the primary amine moieties selected by nitrato-oxygens to form intramolecular hydrogen bonds. Finally, there is a little variation in the equatorial Cu-ONO₂ stereochemistry because of steric hindrance, imposed by the Medpt, preventing large torsional angles by these nitrato ligands. This is evident by comparing the two copper species shown in Finally, nitrate-to-Br ligand exchange was found to take place when KBr pellets are prepared for IR spectral measurements.     

Crystal Structure of Calcium [Aqua(Nitrilotriacetatocobaltate(II)] Tetrahydrate,Ca[Co(Nta)(H2O)]2· 4H2O

Crystals of Ca[Co^II(Nta)]₂· 6H₂O (I), where Nta^3–is a nitrilotriacetate ion, were synthesized and studied using X-ray diffraction analysis. They were found to be monoclinic: a= 6.991(1), b= 10.031(1), c= 16.238(3) Å, = 98.50(1)°, V= 1126.2(3) ų, space group P2₁/n, Z= 2, R ₁= 0.0241, wR ₂= 0.0636, GOOF = 1.050 (for 3132 reflections with I> 2(I)). Structure Iis composed of {[Co(Nta)(H₂O)]^–}₁anion chains united by Ca²⁺cations into a three-dimensional framework. The coordination polyhedra of Co and Ca atoms are distorted octahedra. The Co(II) atom environment includes atoms N(1), O(1), O(3), and O(5) of one Nta^3–ligand, a carbonyl O(2)" atom of the neighboring anion fragment, and an O(w1) atom of the water molecule. The shortest bond is formed by the Co atom with the bridging O(2)" atom in trans-position relative to atom N(1). The Co–O(2)" distance (2.029 Å) is noticeably shorter than the other bond lengths, Co–O(Nta) (2.069–2.103 Å), Co–O(w1), and Co–N(1) (2.155 and 2.177 Å, respectively). Cations Ca²⁺are located in the inversion centers and involve in their coordination atoms O(4), O(6), O(w2), and the oxygen atoms symmetrically bond to them and arranged at 2.271(1), 2.420(1), and 2.351(2) Å, respectively. The structural formula of the title compound is {Ca(H₂O)₂[Co(Nta)(H₂O)]₂}₃· 2H₂O.     

Bis-(tetraethylammonium)[tetraazidocuprate(II)] and catena-di-μ-1,1-azido-[di-μ-1,1-azido-bis-(2,4-dimethylpyridine)dicopper(II)]

Two new copper(II) azido complexes, namely bis-(tetraethylammonium)[tetraazidocuprate(II)] (1) and catena-di--1,1-azido-[di--1,1-azido-bis-(2,4-dimethylpyridine)dicopper(II)] (2), have been prepared and characterized by spectroscopic and crystallographic methods. Complex (1) consists of isolated NEt⁺ ₄ cations and [Cu(N₃)₄]^2– anions. The site symmetry around the copper atom in the anion is 4/m. Complex (2) features a 1 D chain structure, five coordinated square pyramidal copper(II) atoms with both azides functioning as -1,1-bridges. The i.r. spectra reveal that both complexes contain asymmetric azido ligands. The solid and solution electronic spectra of (1) and (2) show very strong absorption bands in the visible region associated with N^– ₃ Cu^II charge-transfer transitions. The e.p.r. spectra of powder samples and solutions at room temperature were recorded and discussed.     

Synthesis and Structure of Catena-[Bis(2-Methylimidazole)(μ-Phthalato)cobaltate(II)]

A new coordination compound [Co(Pht)(2-MeIm)₂] (I), where Pht^2–is the deprotonated radical of o-phthalic acid (H₂Pht) and 2-MeIm is 2-methylimidazole, was synthesized. Its structure was established using X-ray diffraction analysis. The crystal is orthorhombic: space group Pca2₁, a= 15.350(3), b= 7.957(2), c= 13.997(3) Å, (calcd.) = 1.505 g/cm³, and Z= 4. The tetrahedral coordination of the Co(II) atom includes two N atoms of two 2-methylimidazole molecules and two oxygen atoms of two carboxyl groups from different acid radicals. The Co–N distances are equal to 2.022(2) and 2.031(2) Å, while the Co–O distances are 1.972(2) and 2.000(2) Å. The carboxyl groups of the Pht^2–radical and the aromatic nucleus form angles of 47.2° and 35.9°, whereas the angle formed by the carboxyl groups themselves is 50.3°. Compound Iis a polymer, which is confirmed by the 1,6-bridging function of the o-phthalic acid radical. The Co···Co distance in a chain is equal to 7.367 Å. Separate chains are united in the crystal into a framework via N–H···O hydrogen bonds.     

Dinuclear Nickel(II) and Zinc(II) Complexes of 2,6-[N,N′-bis(2-hydroxyphenylmethyl)-N,N′-bis(2-pyridylmethyl)aminomethyl]-4-methylphenol

Abstract

The symmetric 'end-off' compartmental proligand 2,6-[N,N′-bis(2-hydroxy-phenylmethyl)-N,N′-bis(2-pyridylmethyl)aminomethyl]-4-methylphenol (H₃L) has been used to generate homodinuclear nickel(II) and zinc(II) complexes. The crystal structures of the complexes reveal that the di-nickel(II) complex is donor asymmetric and the di-zinc(II) complex is coordination number asymmetric. In both complexes non-coordinated acetic acid molecules are tightly hydrogen-bonded to the pendant phenols of the ligand generating a double acid salt of the type[CH₃COO…H…L…H…OOCCH₃]^3? in the dinickel complex and a single acid salt of the type [CH₃COO…H…L]^3? in the dizinc complex. In both cases the ligand periphery has been extended to provide a supraligand in which the donor potential of the original ligand has been enhanced.     

Crystal structure and magnetic properties of catena-poly[bromido[trans (1S,2S)/(1R,2R)-cyclohexane-1,2-diamine copper(II)]-μ3-bromido]

Catena-poly[bromido [trans(1S,2S)/(1R,2R)-1,2-cyclohexane-1,2-diamine copper(II)]-μ₃-bromido], compound 1, exhibits a one-dimensional, coordination polymer structure in which chiral organic ligands are coordinated to a central inorganic ladder. In the structure layers of polymers of different chirality alternate, forming a racemic crystal. Strong, charge assisted hydrogen bonds link neighbouring polymers to form a two-dimensional hydrogen bonded sheet. Below 10 K weak antiferromagnetic interactions are observed between the copper(II) ions.     

Crystal structure of di-μ-amido-bis[diammineplatinum(II)] nitrate

Di-μ-amido-bis[diammineplatinum(II)] nitrate (1) was synthesized as a byproduct during preparation of tetraammineplatinum(II) nitrate. One possible pathway to produce 1 is that [(H₃N)₂Pt(μ- OH)₂Pt(NH₃)₂](NO₃)₂, a well-known complex forming on treatment of cis-Pt(NH₃)₂I₂ with AgNO₃, reacts with aqueous ammonia. The other possible pathway involves deprotonation of [Pt(NH₃)₄](NO₃)₂ to form monomeric Pt(NH₃)₃(NH₂)NO₃ followed by elimination of NH3. Crystals of 1 (from water) are monoclinic (C2/c) with a = 16.834(2) Å, b = 10.573(1) Å, c = 7.415(1) Å, β = 114.846(1)°, and Z = 4. The cationic portion consists of two symmetrical square-planar Pt centers with the inversion center at the midpoint of the Pt(1)???Pt(1A) vector. The Pt(II) ion is coordinated by four N atoms from two ammonia molecules and two bridging amido groups affording a slightly distorted square. The molecules are stacked in such a way that the planes of coordination squares turn out to be parallel to each other with a distance of 3.501 Å. Intermolecular Pt–H interaction between the μ-NH₂ hydrogens and the platinum(II) centers of the adjacent molecule are observed.     

Crystal Structure of catena-[(Tetrakis-μ2-acetato-μ2-4,4'-bipyridine) dicopper(Ⅱ)] Acetonitrile Solvate

The title compound,[Cu2(CH3COO)4(C8H10N2)]n·nCH3CN1 (C8H10N2,4,4'-bipy = 4,4'-bipyridine),has been solvothermally synthesized in CH3CN and characterized by X-ray diffraction.The crystal is of monoclinic,space group Cc with a = 22.626(6),b = 14.012(4),c =15.106(4) (A),β = 107.610(3)°,V = 4565(2) (A)3,C20H23Cu2N3O8,Mr = 560.49,Z = 8,Dc = 1.631 g/cm3,μ = 1.914 mm-1,Flack parameter = 0.48(1),F(000) = 2288,R = 0.042 and wR = 0.)98 for 8887 observed reflections (I ＞ 2σ(I)).It consists of nearly linear one-dimensional chains [Cu2(CH3COO)4(C8H10N2)]n derived from paddle-wheel [Cu2(CH3COO)4] unit linked by 4,4'-bipy,and CH3CN as guest molecule regularly decorates between the chains.     

{Di-μ-bromotetra [N,N′-bis(3,5-dimethylanil)-4-methyl-2,6-bis(imino)phenoxy]-dinickel}bromide

A new bis-Schiff base ligand, N,N-bis(3,5-dimethylanil)-4-methyl-2,6-bis(imino)phenol was prepared by reacting 2,6-diformyl-4-methylphenol with 3,5-dimethylaniline. Treatment of the ligand with (DME)NiBr₂ (DME = 1,2-dimethoxyethane) gave the novel dinuclear bromo-bridged complex, {di--bromotetra [N,N-bis(3,5-dimethylanil)-4-methyl-2,6-bis(imino)phenoxy]dinickel} bromide, whose crystal structure was confirmed by single crystal X-ray analysis. The calculation, via the molecular mechanics method, performs well to reproduce the crystal structure. The complex shows some activity in respect of ethene oligomerization under mild conditions with methylaluminoxane (MAO) as a co-catalyst.     

Oxamidato complexes. Part 4. Electrochemical study of the copper(III)/copper(II) couple in monomeric N,N′-bis(substituent)oxamidatocopper(II) complexes

Summary The electrochemical behaviour of a series of monomeric N,N-bis(substituent)oxamidato copper(II) complexes of formula Na₂[Cu(3,5,3,5-X₄obbz)]·4H₂O [X = Cl (1), Br (2), I (3) and obbz = oxamidobis(benzoato)], Na₂-[Cu(obbz)]·4H₂O (4), Na₂[Cu(5,5-Me₂obbz)]·4H₂O (5), Na₂[Cu(4,5,4,5-(MeO)₄obbz)]·4H₂O(6),Na₂[Cu(obp)]· 3.5H₂O (7) (obp = oxamidobis(propionato)) and Na₂[Cu(pba)]·6H₂O (8), [pba = propylenebis(oxamate)] has been investigated by cyclic voltammetry, rotating disk electrode and coulometry in water and dimethylsulphoxide (dmso) solutions. NaNO₃ (0.1 M) and n-Bu₄NPF₆ (0.1 M) were used as supporting electrolytes in H₂O and dmso respectively, all solutions being thermostatted at 25 °C. In aqueous solution, the complexes show an oxidation peak ranging from 1.19 to 0.86 V (values referred to the s.c.e.), the corresponding reduction being unobserved, even at high scan rates. In dmso, all the complexes exhibit only one oxidation peak ranging from 0.86 to 0.51 V, the corresponding reduction being observed for all of them except for (3). The oxidation potentials are strongly dependent upon the nature of the N,N-substituent of the oxamide. The copper(III)-assisted hydrolysis of the oxamidate ligand is analysed in terms of the lack of planarity of the oxamidate ligand induced by the steric effect of the halogen substituent in the 3-position on the phenyl rings. The influence of the nature of the solvent was also studied.     

μ-phenoxo-bridged binuclear copper(II) complexes

Summary Two -phenoxo-bridged binuclear copper(II) complexes, [Fsal(GG)₂Cu₂Cl₃]·H₂O (1) containing an exogenous chloride-bridge and [Fsal(GG)₂Cu₂(OH)](ClO₄)₂·H₂O (2) containing an exogenous hydroxide-bridge, where {Fsal(GG)₂ = 2,6-bis[N-(acetylglycine)-imino-methylene]-4-methylphenol}, were synthesized. The complexes were characterized be several spectroscopic methods. According to variable temperature magnetic susceptibility measurements (4–300 K), the hydroxide-bridged complex (2) has a weak antiferromagnetic spin exchange integral (J =- 23.6 cm), while the chloride complex (1) has an unusual weak ferromagnetic spin exchange integral (J = + 30.9 cm); both complexes have similar optical spectra in the aqueous solutions.     

Chromium(III) Complexes with Quadridentate Amines. Crystal Structure of [cis-β-Cr(trien)(C2O4)] Cl·2H2O (I) and [Cr2(μ-OH)2(μ-tren)2] Br4·2H2O (II)

[cis-g-Cr(trien) C₂O₄)] Cl·2H₂O (I) (CrC₈H₂₂N₄O₆Cl) crystallizes at 22°C, from deionized water solution as a racemate in space group Pn (No. 7). Lattice constants are: a = 7.193(2), b = 9.1545(12), c = 11.469(2) Å; g = 100.994(13)°; V = 741.3(3) ų and D_calc = 1.603 gcm^-3 (MW = 357.75, Z = 2). A total of 2251 data were collected, using MoK f radiation ( u = 0.71703 Å), over the range 4 h 2 è h 60°; of these, 1441 (independent and with I S 2 σ (I)) were used in the structural analysis. Data were corrected for absorption ( w = 9.81 cm^-1) and the transmission coefficients ranged from 0.8676 to 0.9942. The final R (F) and R_w(F) residuals were 0.0338 and 0.0764, respectively. The cations of (II) exist in the lattice as enantiomeric pairs. [Cr₂( w -OH)₂( w -tren)₂]Br₄ ·2H₂O (II) (Cr₂C₁₂H₄₂N₈O₄Br₄) crystallizes in the monoclinic space group P2₁/n (No. 14) with a = 10.835(2) Å, b= 7.859(3) Å, c = 16.397(2) Å, g = 105.45(2)°, V = 1345.7(5) ų3 and D_calc = 1.940 g cm^-1 (MW = 786.18, Z = 4). A total of 2467 data were collected, using MoK f radiation ( u = 0.71703 Å), over the range 4 h 2 è h 50°; of these, 1450 (independent and with I S 2 σ ( I )) were used in the structural analysis. Data were corrected for absorption ( w =67.79 cm^-1) and the transmission coefficients ranged from 0.5589 to 0.9949. The final R(F) and R_w(F) residuals were 0.0481 and 0.1408, respectively for 2385 observed reflections with ( I S 2 σ ( I )). In the complex cation, the two Cr(III) centers are in a distorted octahedral environment and are bridged by two hydroxide groups and two ethylamine arms, one from each tren ligand, which spans over the binuclear core. Within the bridging moiety, the Cr···Cr separation is 3.005(2) Å, the ° Cr-OH-Cr = 101.3(2)° and ° O-Cr-O = 78.7(2)°, while the average Cr-N bond distance trans to the hydroxo groups (2.085(6) Å) is shorter than the corresponding cis Cr-N distance (2.104(5) Å).