Octahedral Chromophore Research Articles

Mixed‐Metal Monophosphate Tungsten Bronzes Containing Rhodium and Iridium

AbstractSolution combustion synthesis followed by annealing in air led to the MPTB‐related phosphates (Rh1/6W5/6O3)8(PO2)4, (Ir1/6W5/6O3)8(PO2)4 (a=5.258(2) Å, b=6.538(3) Å, c=17.322(8) Å), (Rh1/9W8/9O3)12(PO2)4 and (Rh2/21W19/21O3)14(PO2)4. Single‐crystals of the mixed‐metal (Rh,W)‐MPTBs at m=4 and at m=7 were grown by chemical vapor transport (CVT). Their crystal structures have been refined from X‐ray single‐crystal data {(Rh,W)‐MPTB at m=4: P212121, Z=1, a=5.2232(3) Å, b=6.4966(3) Å, c=17.3819(9) Å, R1=0.032, wR2=0.075 for 1714 unique reflections, 1524 with Fo>4σ(Fo), 66 variables, 1 constraint, composition from refinement (Rh0.15W0.85O3)8(PO2)4; (Rh,W)‐MPTB at m=7: P21/n, Z=1, a=5.2510(4) Å, b=6.4949(5) Å, c=26.685(2) Å, β=90.30(1)°, R1=0.060, wR2=0.163 for 2074 unique reflections, 1894 with Fo>4σ(Fo), 100 variables, comp. from ref. (Rh0.07W0.93O3)14(PO2)4}. These structure refinements show unexpected distribution of Rh and W over the available metal sites. Further characterization (powder reflectance and magnetic measurements) of the (Rh,W)‐MPTB at m=4 and at m=7 suggest for both phases a homogeneity range with respect to the Rh/W ratio and the presence of small amounts of W5+ besides Rh3+ and W6+. Results of the ligand field analysis for the reference material Rh(PO3)3, which is containing the octahedral chromophore [RhIIIO6], are reported (Δo=23200 cm−1, B=490 cm−1).

Hexakis(diethylacetamide)iron(II) hexahalorhenate(IV) ionic salts: X-ray structures and magnetic properties

Two novel FeII–ReIV compounds of general formula [FeII(DEA)6][ReIVX6] where DEA=diethylacetamide and X=Cl (1) and Br (2) have been prepared and magnetostructurally characterised. Complexes 1 and 2 are isomorphic ionic salts that crystallise in the trigonal crystal system with space group R(−3). The rhenium(IV) ion in 1 and 2 is six-coordinate with six chloro (1) or bromo (2) ligands building a regular octahedral chromophore. The FeII ion is also six-coordinate, and bonded to six oxygen atoms from six DEA molecules. [FeII(DEA)6]2+ cations and [ReIVX6]2− anions alternate in the crystal lattice of 1 and 2 generating supramolecular structures whose magnetic properties are dominated by the high anisotropy of the six-coordinate iron(II) and rhenium(IV) ions. Variable-temperature magnetic susceptibility data of 1 and 2 are well reproduced by a model of isolated S=2 (FeII) and S=3/2 (ReIV) centres with high values of the local zero-field splitting. 1 and 2 are the first examples of hexahalorhenate(IV) salts incorporating FeII complex cations to have been magnetostructurally investigated.

Preparation, supramolecular self-organization and thermal behavior of polymeric complex of composition ([Au{S2CN(C3H7)2}2]3[Bi3Cl12]) n with unusual geometry of bismuth(III) complex anion

A reaction of freshly precipitated bismuth(III) N,N-dipropyldithiocarbamate (PDtc) with AuCl3 solution in 2 M HCl was studied. A heteropolynuclear gold(III)-bismuth complex of ionic type [Au{S2CN(C3H7)2}2]3[Bi3Cl12] (I) was isolated by crystallization of products of the heterogeneous reaction from acetone-chloroform (1: 1) solution. Crystal and supramolecular structure of compound I established by X-ray diffraction study includes structurally nonequivalent complex cations [Au{S2CN(C3H7)2}2]+ related to each other as conformers (hereinafter cations A, B, C, and D) in 1: 1: 2: 2 ratio. Due to secondary Au⋯S bonds (3.386–3.617 A), the isomeric cations form trinuclear species of two types: [C⋯A⋯C] and [D⋯B⋯D] that differ in the character of intercationic binding and Au-Au distances. Relatively weak aurophilic Au⋯Au bonds (3.4704(3) A) unite the neighboring cationic triads into zigzag polymeric chains of type (⋯[C⋯A⋯C]⋯[D⋯B⋯D]⋯)n oriented along the crystallographic axis b. The spatial isolation of neighboring chains is provided by discrete trinuclear anions [Bi3Cl12]3− where metal atoms bind four bridging (μ2 and μ3) chlorine atoms, while each bismuth atom forms distorted octahedral chromophore [BiCl6]. The complex tribismuth anion in the structure I is the first example of [Bi3Cl12]3− anion of angle rather than linear structure: Bi(1)Bi(2)Bi(3) angle is 72.358°. The thermal behavior of compound I was studied by simultaneous thermal analysis. The multistage process of thermal destruction includes the thermolysis of dithiocarbamate portion of the complex and [Bi3Cl12]3− accompanied by reduction of gold(III) to metal and release of BiCl3 (followed by its evaporation) and partial formation of Bi2S3. In the temperature range 680–760°C, bismuth sulfide undergoes oxidation to (BiO)2SO4, which decomposes above 760°C to give Bi2O3. Residue after thermolysis of compound I is gold metal and bismuth(III) oxide.

Supramolecular hydrogen-bonding networks constructed from copper(II) chlorobenzoates with nicotinamide: Structure and EPR

Nicotinamide (nia) has been employed as a supramolecular reagent in the synthesis of four copper(II) chloro- and dichlorobenzoate (Clbz/Cl2bz) complexes. The structures of the compounds [Cu(2-Clbz)2(nia)2(H2O)2] (1), [Cu(4-Clbz)2(nia)2(H2O)2] (2), [Cu(3,5-Cl2bz)2(nia)2(H2O)2] (3), and [Cu(2,5-Cl2bz)2(nia)2(H2O)]·H2O (4) were determined. All the investigated compounds 1–4 reveal water molecules as coordinated. Their structures show distorted octahedral chromophores CuIIN2O2O′2, though some are better described as square-planar or square-pyramid due to a large deviation of the axial ligand away from the octahedral z-axis along with different Cu⋯O(axial) lengths. The equatorial positions are occupied in all four cases by two nitrogen (nia-py) atoms and two carboxylate oxygen atoms of two Clbz/Cl2bz ligands, while the axial positions are occupied by water molecules. The EPR spectra reveal for all 1–4 compounds a spin state of S = ½, mostly with axial symmetry of the spectra. Their resolution is clearly dependant to the crystal symmetry related equivalence of the magnetic sites. The coordination molecules of all compounds are connected by N–H⋯O and O–H⋯O H-bonds from nicotinamide NH2 groups, carboxylate anions and/or water molecules, which create supramolecular chains or further H-bonded into 2D sheets. Steric hindering of the chlorine atoms of the Clbz/Cl2bz, especially seen at the coordination of the water molecules, demonstrates its role at the coordination sphere appearance. Despite this influence, the water molecules in 1–4 always assist at the similar supramolecular H-bonded network, almost at the same manner.

L-Tyrosinatonickel(II) Complex: Synthesis and Structural, Spectroscopic, Magnetic, and Biological Properties of 2{[Ni(l-Tyr)2(bpy)]}·3H2O·CH3OH

The complex 2{[Ni(L-Tyr)2(bpy)]}·3H2O·CH3OH [1, where L-Tyr = L-tyrosine; bpy = 2,2'-bipyridine (2,2'-bpy)] was obtained in crystalline form and characterized by X-ray and spectroscopic (FT-IR, NIR-vis-UV, and HFEPR) and magnetic methods. The complex crystallized in the hexagonal system with a = b = 12.8116(18) Å, c = 30.035(6) Å, and space group P3221. The six-coordination sphere around the Ni(2+) ion is formed by two N and two O L-tyrosinato atoms and completed by two N atoms of the 2,2'-bpy molecule. Neighboring [Ni(L-Tyr)2(bpy)] units are joined via weak hydrogen bonds, which create a helical polymeric chain. The coordinated atoms form a strongly distorted cis-NiN2N2'O2 octahedral chromophore. The solid-state electronic spectrum of complex 1 was analyzed assuming D2h symmetry, and the observed bands were assigned to (3)B1g → (3)Ag, (3)B1g → (3)B3g, (3)B1g → (3)B2g, (3)B1g → (3)B3g, (3)B1g → (3)B1g, and (3)B1g → (3)B2g transitions for the I and II d-d bands, respectively. The crystal-field parameters found for D2h symmetry are Dq = 1066 cm(-1), Ds = 617 cm(-1), Dt = -93 cm(-1), B22 = 7000 cm(-1), and Racah B = 812 cm(-1). Magnetic studies revealed the occurrence of hydrogen-bonded metal pairs. The spin Hamiltonian parameters D = -3.262 cm(-1) and E = -0.1094 cm(-1), determined from high-field, high-frequency electron paramagnetic resonance spectra, together with a weak antiferromagnetic exchange parameter J = -0.477 cm(-1), allowed us to reproduce the powder magnetic susceptibility and field-dependent magnetization of the complex. The biological activity of 1 has been tested by using the Fusarium solani, Penicillium verrucosum, and Aspergillus flavus fungi strains and Escherichia coli, Pseudomonas fluorescens, Serratia marcescens, and Bacillus subtilis bacterial strains.

Turning on Red and Near-Infrared Phosphorescence in Octahedral Complexes with Metalated Quinones

We report the synthesis of π-bonded ruthenium, rhodium, and iridium o-benzoquinones [Cp*M(o-C(6)H(4)O(2))](n) [M = Ru (2), n = 1-; Rh (3), n = 0; Ir (4), n = 0] following a novel synthetic procedure. Compounds 2-4 were fully characterized by spectroscopic methods and used as chelating organometallic linkers, "OM-linkers", toward luminophore bricks such as Ru(bpy)(2)(2+), Rh(ppy)(2)(+), and Ir(ppy)(2)(+) (bpy = 2,2'-bipyridine; ppy = 2-phenylpyridine) for the design of a novel family of octahedral bimetallic complexes of the general formula [(L-L)(2)M(OM-linkers)][X](m) (X = counteranion; m = 0, 1, 2) whose luminescent properties depend on the choice of the OM-linker and the luminophore brick. Thus, dinuclear assemblies such as [(bpy)(2)Ru(2)][OTf] (5-OTf), [(bpy)(2)Ru(2)][Δ-TRISPHAT] (5-ΔT) {TRISPHAT = tris[tetrachlorobenzene-1,2-bis(olato)]phosphate}, [(bpy)(2)Ru(3)][OTf](2) (6-OTf), [(bpy)(2)Ru(4)][OTf](2) (7-OTf), [(bpy)(2)Ru(4)][Δ-TRISPHAT](2) (7-ΔT), [(ppy)(2)Rh(2)] (8), [(ppy)(2)Rh(3)][OTf] (9-OTf), [(ppy)(2)Rh(4)][OTf] (10-OTf), [(ppy)(2)Rh(4)][Δ-TRISPHAT] (10-ΔT), [(ppy)(2)Ir(2)] (11), [(ppy)(2)Ir(3)][OTf] (12-OTf), [(ppy)(2)Ir(4)][OTf] (13-OTf), and [(ppy)(2)Ir(4)][Δ-TRISPHAT] (13-ΔT) were prepared and fully characterized. The X-ray molecular structures of three of them, i.e., 5-OTf, 8, and 11, were determined. The structures displayed a main feature: for instance, the two oxygen centers of the OM-linker [Cp*Ru(o-C(6)H(4)O(2))](-) (2) chelate the octahedral chromophore metal center, whether it be ruthenium, rhodium, or iridium. Further, the carbocycle of the OM-linker 2 adopts a η(4)-quinone form but with some catecholate contribution due to metal coordination. All of these binuclear assemblies showed a wide absorption window that tailed into the near-IR (NIR) region, in particular in the case of the binuclear ruthenium complex 5-OTf with the anionic OM-linker 2. The latter feature is no doubt related to the effect of the OM-linker, which lights up the luminescence in these homo- and heterobinuclear compounds, while no effect has been observed on the UV-visible and emission properties because of the counteranion, whether it be triflate (OTf) or Δ-TRISPHAT. At low temperature, all of these compounds become luminescent; remarkably, the o-quinonoid linkers [Cp*M(o-C(6)H(4)O(2))](n) (2-4) turn on red and NIR phosphorescence in the binuclear octahedral species 5-7. This trend was even more observable when the ruthenium OM-linker 2 was employed. These assemblies hold promise as NIR luminescent materials, in contrast to those made from organic 1,2-dioxolene ligands that conversely are not emissive.

Synthesis, Characterization, and Crystal Structure of Bis(2,2′-Dipyridyl) (Nitropyridylsulfide) Ruthenium(II) (Hexafluorophosphate)

The S‒S bond undergoes a reductive cleavage when 2,2′-dithiobis(5-nitropyridine) is reacted with Ru(bpy)2Cl2 (bpy = 2,2′-bipyridine) and yields the monocationic species [Ru(bpy)2(S-Py-NO2)]+. The synthesized complex Ru(N5S)+ was characterized by UV-visible (UV-Vis), cyclic voltammetry, FT-IR, 1H-NMR, and X-ray. The 1H-NMR spectra show a set of signals according to low complex symmetry. The electrochemistry analysis showed a quasi-reversible RuIII/II wave observed at 0.78 V versus Ag/AgCl. X-ray structural analysis revealed a distorted octahedral coordination sphere around the metal. The octahedral N5S chromophore surrounding the metal ion is formed via two trans N and S atoms and four nitrogen atoms from two bis(2,2′-bipyridiyl) ligands. The distortion provoked by an N,S-schelating short-bite ligand has already been shown in similar derivatives. In the title compound, this effect is more dramatic since the four-membered ring presents more strain, and this effect is similar to the previously analyzed four-membered N,S-chelating short-bite ligand.

Supramolecular Structure, Thermal and Spectroscopic Properties of a New Coordination Polymer: Catena-Bis(μ2-4,4′-dipyridyldisulfide-κ2N,N′)-Bis(AQUO)-Copper(II)di-trifluoromethanesulfonate

A new supramolecular network of copper (II), [{Cu(bpds)2(H2O)2}] • 2CF3SO3]n, (I), (bpds = 4,4′-bipyridildisulfide) has been synthesized and characterized by elemental analysis and Fourier transform infrared (FT-IR) and its structure determined using X-ray crystallography. The thermal decomposition mechanism of the complex was studied by using thermogravimetry-derivative thermogravimetry (TG-DTG) techniques. X-ray structural analysis revealed that the coordination polymer displays 1D chains. The octahedral O2N4 chromophore surrounding the metal ion forms via two trans located water oxygen and four nitrogen from four bpds ligand. The structure consists of Cu(H2O)2 fragments linked by pairs of bpds ligand to form a double-stranded chain. The thermogravimetric analysis indicates sequential loss of adsorbed and coordinated water and triflate counter ion, prior to more comprehensive ligand fragmentation at elevated temperatures.

Cobalt(II) complexes of new biomimetic polydentate amide: Spectroscopic, kinetics of thermal decomposition and XRPD studies

Complexes of Co(II) with new ligands N′, N″-bis(3-carboxy-1-oxoprop-2-enyl) 2-amino- N-arylbenzamidine (C 21H 17N 3O 6), N′, N″-bis(3-carboxy-1-oxopropanyl) 2-amino- N-arylbenzamidine (C 21H 21N 3O 6) and N′, N″-bis(3-carboxy-1-oxophenelenyl) 2-amino- N-arylbenzamidine (C 29H 21N 3O 6) have been synthesized and characterized by elemental analyses, vibrational spectra, electronic spectra, TOF-mass spectra, magnetic susceptibility measurements, thermal studies and X-ray powder diffraction studies. Vibrational spectra indicate coordination of amide and carboxylate oxygen of the ligands along with two water molecules giving a MO 6 weak field octahedral chromophore. Electronic spectra and magnetic susceptibility measurements reveal octahedral geometry for Co(II) complexes. The elemental analyses and mass spectral data have justified the ML complexes. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first-order kinetics. Powder diffraction determines the cell parameters of the complexes.

Nickel(II) complexes of new polydentate carboxyamide: spectroscopic, kinetics of thermal decomposition and X-ray powder diffraction studies

Complexes of NiII with new ligands N′,N′′-bis(3-carboxy-1-oxoprop-2-enyl), 2-Amino-N-arylbenzamidine (C21H17N3O6), N′,N′′-bis(3-carboxy-1-oxopropanyl) 2-Amino-N-arylbenzamidine (C21H21N3O6) and N′,N′′-bis(3-carboxy-1- oxophenelenyl) 2-Amino-N-arylbenzamidine (C29H21N3O6) have been synthesized and characterized by elemental analyses, vibrational spectra, electronic spectra, TOF-mass spectra, magnetic susceptibility measurements, thermal studies and X-ray powder diffraction studies. Vibrational spectra indicate coordination of amide and carboxylate oxygen of the ligands along with two water molecules giving a MO6 weak field octahedral chromophore. Electronic spectra and magnetic susceptibility measurements reveal octahedral geometry for NiII complexes. The elemental analyses and mass spectral data have justified the ML complexes. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. The crystal data: C21H19N3O8 Ni is orthorhombic, space group Pmmm, a = b = 9.015360(A), c = 10.554430(A), V = 572.11A3; C21H23N3O8Ni is monoclinic, space group P2/m, a = 15.08206(A), b = 5.358276(A), c = 9.898351(A), V = 671.58A3; C29H23N3O8Ni is tetragonal, space group P4/m, a = b = 6.328104(A), c = 9.82213(A), V = 393.33A3. Molecular structures of the complexes have been optimized by MM2 calculations and supported octahedral arrangements around Nickel(II) ions.

Structural systematics of the [Cu(chelate)3][Y]2series. An interesting crystallographic structural insight involving vibronic coupling and the Jahn–Teller effect (JTE). The syntheses and low temperature crystal structures of tris(2,2′bipyridyl)copper(ii) tetraphenylborate and tris(2,2′bipyridyl)zinc(ii) tetraphenylborate

The crystal structures of [Cu(bipy)(3)][BPh(4)](2), 1, and [Zn(bipy)(3)][BPh(4)](2), have been determined at low temperature. 1 and 2 are closely related, but are not isostructural. Both contain a two-dimensional supramolecular construct (SC) involving a sandwich structure. 1 has a six-coordinate CuN(6) chromophore with a regular elongated octahedral stereochemistry and rhombic in-plane bond lengths. The associated tetragonality value, T, of 1 is 0.8868. 2 involves a six-coordinate octahedral chromophore. Differences between 1 and 2 relate to the tendency of copper(II) complexes to undergo a Jahn-Teller (JT) distortion. The zinc(II) cation feels solely the host site strain, whereas the copper(II) cation also involves vibronic JT type coupling. The copper polyhedron geometry is characterized by both phenomena, with the vibronic interaction dominating. Scatter plot analysis involving the tris-chelate copper(II) series suggests that neither pure Q(theta) or Q(epsilon) components or the a(2u) mode operate in isolation over the entire series. All three operate in combination with varying quantifiable contributions, leading to distortion from the regular tetragonal octahedral stereochemistry.

The crystal structure and electronic properties of a cis-distorted octahedral CuN 4O 2 chromophore: [Cu(dpyam) 2(OXO)] +, OXO=ONO −, O 2CH − and ONO 2−

The crystal structures of three bis(dpyam)copper(II) complexes, [Cu(dpyam) 2(NO 2)](NO 2) ( I) and [Cu(dpyam) 2(O 2CH)](ClO 4) ( II) and [Cu(dpyam) 2(ONO 2)](BF 4) ( III) have been determined by X-ray analysis. In I, the copper atom and the asymmetrically bonded nitrito group lie on a crystallographic C 2-axis. The nitrito group is clearly disordered about the C 2-axis giving a square pyramidal cis-distorted octahedral (4+1+1 *) chromophore rather than a pseudo-regular cis-distorted octahedral chromophore. In II and III, a distortion of the cis-distorted CuN 4O 2 chromophore towards a square pyramidal (4+1+1 *) stereochemistry is also present. The polycrystalline EPR spectra of I– III together with the high asymmetry in geometry of the CuN 4O 2 chromophores are suggesting that all complexes appear to be near the static distortion limit of the fluxional CuN 4O 2 chromophore geometry. The electronic reflectance spectra of the three complexes involve two bands at the same intensity corresponding to a cis-distorted octahedral geometry.

The langbeinite-type barium vanadium(III) orthophosphate, Ba3V4(PO4)6

Langbeinite-type Ba3V4(PO4)6 has been crystallized from a stoichiometric melt starting from Ba(PO3)2 and V2O3. The crystal structure has been refined from single-crystal X-ray diffraction data. It consists of a vanadato(III)–phosphate network [V4(PO4)6]6−, which shows some resemblance to the NASICON structure type. A new method is presented for the visualization of this structural relationship. The single-crystal electronic spectrum of yellow–green Ba3V4(PO4)6 shows the absorption bands typical for the octahedral chromophore [VIIIO6].

The synthesis, crystal structures and infrared spectra of bis(2,2′-bipyridyl)mononitratozinc(II) hexafluorophosphate and bis(2,2′-bipyridyl)mononitratozinc(II) perchlorate: A comparison with existing [Zn(chelate)2(OXO)][Y] and [Cu(chelate)2(OXO)][Y] complexes of known crystal structure

In order to extend the number of [Zn(chelate)2(OXO)][Y] complexes, with chelate =2,2″ bipyridyl, 1,10 phenanthroline and 2,2″-bipyridylamine and (OXO)-=(ONO)-, (O2NO)-, (O2CCH2)- and (O2CH)-, the crystal structures and infrared spectra of [Zn(bipy)2(O2NO)][PF6], (9) and [Zn(bipy)2(O2NO)][ClO4], (10) have been determined. Both zinc(II) complexes involve a slightly elongated cis-distorted ZnN4O2 chromophore.The slight elongation contrasts with the more significant compressed cis-distorted octahedral CuN4O2 chromophore of the corresponding copper(II) structures. The Zn‐O bonds in (9) are 2.186(3) and 2.351(3)Å (ΔO0.165(3)Å), while the corresponding Zn‐O(1) and Zn‐O(2) bonds in (10) are 2.194(2) and 2.355(2)Å (ΔO0.161(2)Å), respectively. The mean Zn‐O bond distance in (9) is 2.269(3) and 2.275(2)Å in (10). Although the significant cis-distortion of the Zn‐O distances is comparable to the analogous Cu‐O distances, the ΔO values are notably smaller. The thermal ellipsoids of (9) and (10), which are slightly asymmetric (ΔO ≈ 0.16Å), are small and isotropic. Such differences reflect the spherical symmetry of the d 10 zinc(II) configuration relative to the nonspherical symmetry of the d 9 copper(II) ion.The ZnN4O2 chromophores of (9) and (10) are similar, indicating the isomorphous and isostructural nature of the complexes. Both complexes have a common back-angle or magic angle of α≈117°, in contrast to the bipyam complexes where the back-angle is much less at ≈105°, related to the conformation of the floppier bipyam chelate ligand.

Cobalt(II) complexes of new biomimetic polydentate amide ligands. A spectroscopic, thermal and potentiometric study

Complexes of CoII with N,N′-bis-(3-carboxy-1-oxopropanyl)-1,2-ethylenediamine(L1), N,N′-bis-(3-carboxy-1-oxopropanyl)-1,2-phenylenediamine(L2), N,N′-bis-(2-carboxy-1-oxophenelenyl)-1,2-phenylenediamine(L3) and N,N′-bis-(3-carboxy-1-oxoprop-2-enyl)-1,2-phenylenediamine(L4) have been prepared and characterized by elemental analysis, vibrational spectra, magnetic susceptibility measurements, electronic spectra and thermal studies. Stability constants of the complexes have been evaluated potentiometrically. Vibrational spectra indicate coordination of amide and carboxylate oxygens of the ligands along with two water molecules giving a MO6 weak field octahedral chromophore. Electronic spectra support octahedral geometry around CoII. The [Co(L1)-(H2O)2] · 2H2O complex has the maximum activation energy and [Co(L3)(H2O)2] complex has the minimum activation energy. The order of stability constants of the CoII complexes with various ligands is due to their σ-donor abilities.

Unprecedented Change of the Jahn−Teller Axis in a Centrosymmetric CuII Complex Induced by Lattice Water Molecules − Crystal and Molecular Structures of Bis[bis(3,5‐dimethylpyrazol‐1‐yl)acetato]copper(II) and Its Dihydrate

AbstractTwo copper coordination compounds with the tridentate (NON) ligand bis(3,5‐dimethylpyrazol‐1‐yl)acetic acid (Hbdmpza) are reported. The central coordination sphere in both compounds is fulfilled by two ligands in [CuL2]. The ligands are centrosymmetrically oriented around the copper ion, thus forming a trans‐CuN4O2 elongated octahedral chromophore. The atoms in both compounds are not positioned at the same places in the Jahn−Teller‐distorted octahedral environment. For compound [CuL2] (1) two nitrogen atoms are located on the longer axis [Cu−N: 2.438(2) Å], while the other two nitrogen atoms [Cu−N: 2.006(2) Å] and the two oxygen atoms [Cu−O: 1.983(2) Å] form the basal plane of the octahedron. The coordination sphere for [CuL2]·2H2O (2) is composed of four nitrogen atoms [Cu−N: 2.013(3), 2.038(2) Å] that form the basal plane, while the two oxygen atoms are at a longer distance [Cu−O: 2.293(2) Å]. The water molecules in 2 are hydrogen bonded to the non‐coordinated carboxylate oxygen atoms, forming bridges between two neighbouring monomeric units and leading to an infinite chain. Significant differences are observed for both compounds by spectroscopic investigations (EPR, IR, ligand field). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Fluxional chromophores of bis(di-2-pyridylamine)nitritocopper(II) cations: crystal structures and electronic properties of the complexes bis(di-2-pyridylamine)nitritocopper(II) nitrate and bis(di-2-pyridylamine)nitritocopper(II) perchlorate

The X-ray crystal structures of two cation-distortion isomers of [Cu(dpyam) 2(ONO)](NO 3) ( 1) and [Cu(dpyam) 2(ONO)](ClO 4) ( 2) complexes are reported and shown to contain an asymmetric cis-distorted CuN 4O 2 chromophore. In 1 the copper atom and the asymmetrically bonded nitrito group lie on a crystallographic C 2 axis. The nitrito group is clearly disordered about the C 2 axis giving a square pyramidal cis-distorted octahedral (4+1+1*) chromophore rather than a pseudo regular cis-distorted octahedral chromphore. In 2 a distortion of the CuN 4O 2 chromophore towards a square pyramidal (4+1+1*) geometry is also present, but with well-ordered and less asymmetric nitrito group. The polycrystalline ESR spectra of 1 and 2 are temperature independent suggesting that both complexes appear to be near the static distortion limit of the fluxional CuN 4O 2 chromophore geometry. The electronic reflectance spectra of 1 and 2 involve two bands at approximately 14 700 and 9800 cm −1 for 1, and approximately 14 970 and 10 000 cm −1 for 2 and relate to the underlying static CuN 4O 2 (4+1+1*) chromophore geometry.

Novel trinuclear and dinuclear nickel coordination compounds with a new pentadentate ligand. Crystal structures of [Ni3(bdnol)(EtOH)Cl5] and [Ni2(bdnol)Cl3

The pentadentate ligand 1,9-bis(3,5-dimethyl-1-pyrazolyl)-3,7-dithianonan-5-ol (Hbdnol)yields, with nickel chloride, the unique trinuclear compound [Ni3(bdnol)(EtOH)Cl5] with two [NiNSOCl3] and one [NiCl4OO′] distorted octahedral chromophores, and the dinuclear compound [Ni2(bdnol)CI3], with two [NiNSOCl2] distorted trigonal bipyramidal chromophores.

Coordination Behaviour of Pyridoxalisonicotinoyl Hydrazone Towards Some 3d-Metal Ions

Abstract The complexes of divalent manganese, cobalt, nickel, copper, zinc and the ligand pyridoxalisonicotinoyl hydrazone (PIH) are discussed in order to illustrate the behaviour of the ligand towards the metal ions in acidic and neutral media. The complexes [M(PIH-2H)(H2O)3] (M = Mn, Co and Zn), [Cu(PIH-2H)(H2O)2]2, [Cu(PIH)Cl(H2O)]2 2+ and [Ni(PIH)Cl2(H2O)] have distorted octahedral structures. The isostructural crystalline complexes, [M(PIH)C12]2 (M = Mn, Co and Zn) are isolated from hot solutions. The electronic spectral data of cobalt in conjunction with infrared, NMR and magnetic measurements enables the assignment of the formula [M(PIH)2][MCI4] to these complexes. The anion is tetra-hedral while the cation has an octahedral chromophore. Characterization data indicates that [Ni(PIH-2H)H2O] has a four-coordinated square-planar chromophore. The IR, 1H and 13C NMR spectral data indicate that PIH behaves as a neutral tridentate ligand in the chloro complexes and as a dinegative, tridentate species in t...

Transition metal complexes of two related pyrazole containing ligands:3,6-dimethyl-1,8-(3,5-dimethyl-1-pyrazolyl)-3,6-diazaoctane (ddad) and 1,4-bis(2-ethyl-(3,5-dimethyl-1-pyrazolyl))-piperazine (bedp). Synthesis, spectroscopy and X-ray structures

Several coordination compounds with the ligand 3,6-dimethyl-1,8-(3,5-dimethyl-1-pyrazolyl)-3,6-diaza- octane (ddad) were obtained: (Cu, Ni)(ddad)(BF 4) 2, Co(ddad)(H 2O)(BF 4) 2, (Co, Ni, Cu, Zn) 2(ddad)Cl 4, Co 3(ddad) 2(NCS) 6 and Cu 2(ddad)(NCS) 3. Five X-ray structures were obtained, viz. of [Cu(ddad)](BF 4) 2, [Ni(ddad)](BF 4) 2, Ni(ddad)(NCS) 2, [Ni(bedp)](H 2O)(BF 4) 2 and [Cu(bedp)](H 2O)(BF 4) 2, but the data did not allow the calculation of very accurate bond lengths. However, the basic coordination geometries were obtained in all cases. The coordination by the ligands is square planar, while Ni(ddad)(NCS) 2 contains additional trans coordinating thiocyanate anions. The asymmetric unit of [Cu(ddad)](BF 4) 2 contains two almost identical [Cu(ddad)] 2+ species. The coordination of the copper atoms in both molecules is intermediate between tetrahedral and square planar. One molecule [Cu(ddad)] 2+ is the (R,R) diastereoisomer of the ligand and the other is the (S,S) diastereoisomer. The chloride compounds are, except for Ni(II), all dinuclear with MN 2Cl 2 chromophores. The nickel(II) compound contains square planar Ni(ddad) 2+ cations and tetrahedral NiCl 4 2- anions. The thiocyanate compound of Ni(II), which is isomorphous with the corresponding Zn(II) compound, has octahedral MN 2N 2′N 2″ chromophores. The cobalt compound crystallizes as [Co(ddad)(NCS)] 2Co(NCS) 4 with five coordinate cobalt in the cation. With copper thiocyanate ddad forms the mixed-valence compound Cu 2(ddad)(NCS) 3, with [Cu(ddad)] 2+ and [Cu(NCS) 3] 2-. With the ligand, 1,4-bis(2-ethyl-(3,5-dimethyl-l-pyrazolyl))-piperazine (bedp) the compounds [(Ni, Cu)Coedp)](H 2O)(BF 4) 2, (Ni, CO)Coedp)(NCS) 2, Zn 2(bedp)(NCS) 4, (Ni, Co, Cu, Zn) 2(bedp)Cl 4 and Cu 2(bedp)(NCS) 3 were obtained. The chloride compounds form dinuclear compounds (similar to ddad) with MN 2Cl 2 chromophores. However, in addition to the green form of [Ni(bedp)][NiCl 4] a purple isomer Ni 2(bedp)Cl 4, with a tetrahedral NiN 2Cl 2 chromophore, was obtained. The ligand field spectra of Ni(bedp)(NCS) 2 and the isomorphous cobalt compound show typical octahedral chromophores. With copper thiocyanate a mixed-valence compound was formed, with a structure likely to be similar to the corresponding ddad compound, viz. [Cu(II)(bedp)][Cu(I)(SCN) 3].