Mononuclear pivalates of metals of the first transition series

The synthesis and structures of mononuclear Ni(II), Co(II), Mn(II), and Cu(II) pivalates isolated as complex salts NBu₄[M(Piv)₃] ((NBu₄)⁺ is tetrabutylammonium cation, Piv^– is pivalate anion) and polynuclear complexes [Ni₆(L)₂(HL)₂(Piv)₆(HPiv)₈], (NBu₄)₂[Co₄(Piv)₈(AcO)₂(H₂O)₄], NBu₄[Co₂(Piv)₅(H₂O)₂], and (NBu₄)₂[Cu₄(Piv)₈(AcO)₂(H₂O)₂] (L^2–, HL^–, and AcO^– is lactic acid dianion, lactic acid monoanion, and acetate anion, respectively) are discussed. The formation of the compounds is detected during the development of the synthesis of NBu₄[M(Piv)₃].     

Nickel(II) and cobalt(II) coordination compounds of dichloroguanidinopyrimidines

Summary New coordination compounds of Ni^II and Co^II with dichloropyrimidinoguanidine (L) have been obtained and characterized by physico-chemical and spectroscopic methods. The complexes have the general formulae: [ML₃](ClO₄)₂, [ML₂(SO₄)], [ML₂(NCS)₂], (M = Ni or Co), [NiL₂(ClO₄)₂] and [CoL₂](ClO₄)₂. The ligands are bonded to the metal ion via one nitrogen atom from the pyrimidine heterocyclic ring and one from the guanidine group.     

Bis(2,6‐di­amino‐3,5‐di­bromo­pyridinium) tetra­bromo­cuprate(II)

The title compound, (C₅H₆Br₂N₃)₂[CuBr₄], contains isolated substituted pyridinium cations and [CuBr₄]^2? anions. The di­amino­di­bromo­pyridinium ions are planar, while the Cu^II ions have a distorted compressed tetrahedral coordination with C₂ symmetry. The two independent trans‐Br—Cu—Br angles are 128.9 (1) and 136.0 (1)°, with Cu—Br distances of 2.3939 (15) and 2.3790 (16) Å.     

Copper and copper-palladium catalysts of aliphatic thiols oxidation in biological objects: Quantum-chemical DFT simulation

DFT calculations (M06, PBE0/Def2-TZVP) of coordination compounds used in reactions of selective oxidation of thiols to disulfides were performed. Primary active centers of the catalysts are polynuclear scaffolds {L₂M(μ-OH)₂ML₂}²⁺ and {L₂M(μ-OH)₂M′(μ-OH)₂ML₂}²⁺ (M = Cu^I, Cu^II, Pd^II; M' = Cu^II; L = NH₃). Cu^II ions in combination with PdII ions are capable of formation of polynuclear active center {PdII(μ-OH)₂Cu^II(μ-OH)₂Pd^II}²⁺ bringing together a large number of mutually oriented RS^– groups and thus affecting the rate of formation of disulfide R₂S₂.     

Bis(2‐amino‐2‐thiazolinium) tetra‐μ‐formato‐κ8O:O′‐bis[(formato‐κO)copper(II)]

In the title dimeric compound, (C₃H₇N₂S)₂[Cu₂(CHO₂)₆], each Cu^II atom has a square‐pyramidal coordination, with the nonbridging formate ion at the apical position. The complex anion is located on a crystallographic inversion centre, with a Cu...Cu separation of 2.6566 (4) Å. 2‐Amino‐2‐thiazolinium cations connect complex anions via hydrogen bonds to form a ribbon running along the a axis.     

Di‐μ‐hydroxido‐bis{[bis(6‐methyl‐2‐pyridylmethyl)(2‐phenylethyl)amine‐κ3N′,N′′,N′′′]copper(II)} bis(perchlorate)

The title compund, [Cu₂(OH)₂(C₂₂H₂₅N₃)₂](ClO₄)₂, is a copper(II) dimer, with two [CuL]²⁺ units [L is bis(6‐methyl‐2‐pyridylmethyl)(2‐phenylethyl)amine] bridged by hydroxide groups to define the {[CuL](μ‐OH)₂[CuL]}²⁺ cation. Charge balance is provided by perchlorate counter‐anions. The cation has a crystallographic inversion centre halfway between the Cu^II ions, which are separated by 3.0161 (8) Å. The central core of the cation is an almost regular Cu₂O₂ parallelogram of sides 1.931 (2) and 1.935 (2) Å, with a Cu—O—Cu angle of 102.55 (11)°. The coordination geometry around each Cu^II centre can be best described as a square‐based pyramid, with three N atoms from L ligands and two hydroxide O atoms completing the coordination environment. Each cationic unit is hydrogen bonded to two perchlorate anions by means of hydroxide–perchlorate O—H...O interactions.     

Synthesis and physico-chemical characterization of coordination compounds of 3d metals with potassium bicyclo[2.2.1]-hept-5-en-endo-2-oyl-hydroxylamine-3-carboxylate

Summary The ligand, potassium bicyclo[2.2.1]-hept-5-en-endo-2-oyl-hydroxylamine-3-carboxylate-monohydrate, KHL·H₂O₂ and its M(HL)₂ complexes, [{Fe(HL)₂}₂SO₄], K[FeL₂] and K₂[ML₂] (M=Mn^II, Fe^II, Co^II, Ni^II, Cu^II and Zn^II) were prepared and characterized. For all, except the sulphate complex of iron(III), a monomeric octahedral configuration was postulated and this is realized through the coordination of oxygen atoms of the carboxylic, carbonyl and oxime group of two mono-or di-anion ligands. The dianionic form of the ligand is the result of deprotonation of the carboxylic group and mide-alcohol form of the hydroxamic group. For the sulphate-containing iron(III) complex a dimeric coordination is proposed with two monoanions of the organic ligand (the carbonyl oxygens are not coordinated) and the bridging SO₄ group. The relative degree of covalency of the metal-carboxylic oxygen bond is 10.6–45.2% and increases in the order: Mn^IIIIIIIIIIIII. The complexes have been characterized by elemental and t.g. analysis and i.r. spectra.     

Voltammetry as Virtual Potentiometric Sensor in Modelling of a Metal/Ligand System and Refinement of Stability Constants. Part 5

The concept of virtual potential (employed here in modelling operations), a unique experimental setup designed and built in our laboratories, and new regression equations derived for nonlinear fitting of quasi‐reversible direct‐current polarograms were combined with the existing rigorous treatment and refinement of polarographic data to establish reliable metal/ligand models and accurate stability constants for the lead(II)/glycine/OH^? and lead(II)/sarcosine/OH^? systems (sarcosine = N‐methylglycine). In the case of glycine, the complexes [M(HL)], [ML], [ML₂], and [ML₃] were identified, and their stability constants (as log β) were established to be 10.51 ± 0.06, 4.58 ± 0.02, 7.19 ± 0.10, and 9.27 ± 0.02, respectively, the complex [ML₃] being reported here for the first time (Table 2). The system with sarcosine involving [M(HL)], [ML], [ML₂], [ML₃], and [ML₂(OH)₂], with the stability constants (as log β) 11.01 ± 0.04, 4.18 ± 0.03, 7.23 ± 0.03, 9.1 ± 0.3, and 15.97 ± 0.07, respectively, is reported for the first time (Table 3). The log K₁ value for Pb^II with sarcosine is a fraction of a log unit smaller when compared with the Pb^II complex with glycine, in agreement with the literature data for Cu^II, Ni^II, and Zn^II showing the same trend for these two ligands. The proposed nonlinear curve‐fitting operations expand the applicability of polarography to study reliably and conveniently quasi‐reversible, on the polarographic time scale, metal/ligand systems (systems with involved heterogeneous kinetics).     

Synthesis and characterization of a complex salt and heterobimetallic coordination polymers of 1-benzoyl-1-cyanoethylene-2,2-dithiolate

The complex salt (NBu₄ⁿ)₂ [Cu(bcd)₂] and heterobimetallic coordination polymers MM′(bcd)₂ [M=2Ag^I, Cd^II, Hg^II or Pb^II; M′=Ni^II or Cu^II; bcd²⁻=1-benzoyl-1-cyanoethylene-2,2-dithiolate] have been synthesized from the reaction of Na₂[M′(bcd)₂] generated in situ with NBu₄ⁿBr or metal salts MX₂ [X=MeCO₂⁻, NO₃⁻, Cl⁻ or SO₄²⁻]. The complexes were characterized by elemental analyses, molar conductance, magnetic susceptibility, i.r., n.m.r., electronic and e.s.r. spectra and solid-state conductivity measurements. The MCu(bcd)₂ polymers are diamagnetic, suggesting strongly antiferromagnetically coupled Cu^II ions. The conductivities of the pressed pellets of the compounds are very small and they do not show semiconducting behaviour in the considered temperature range.*Presented at the 10th Symposium on Modern Trends in Inorganic Chemistry (MTIC-X), December 15–17, 2003, Indian Institute of Technology, Mumbai, India.     

trans-Bis(3-aminoflavone-κ2N,O)bis(perchlorato-κO)copper(II), a new potential antitumour agent

The title compound, trans-bis(3-amino-2-phenyl-4H-1-benzopyran-4-one-κ²N,O⁴)bis(perchlorato-κO)copper(II), [Cu(ClO₄)₂(C₁₅H₁₁NO₂)₂], is composed of mononuclear units wherein the central Cu^II cation occupies a crystallographic inversion centre. The cation is coordinated by two bidentate 3-aminoflavone ligands occupying the equatorial sites and by two perchlorate anions in the apical positions, thereby giving rise to a markedly elongated octahedral coordination geometry. Two symmetry-related intermolecular N—H...O hydrogen bonds link the molecules into chains of rings running parallel to the [100] direction, while intramolecular N—H...O hydrogen bonds help to determine the orientation of the apical perchlorate anions.     

MII-N-diisopropoxythiophosphorylthiobenzamide complexing processes in M2[Fe(CN)6]-gelatin-immobilized matrices (M = Co,Ni, Cu)

Complexing processes in M^II-N-diisopropoxythiophosphorylthiobenzamide binary systems (M = Co, Ni, Cu) in metal(II) hexacyanoferrate(II) gelatin-immobilized matrices upon contact with aqueous–alkaline (pH = 12.0 ± 0.1) solutions of organic compounds have been studied. It has been shown that, in Co^II and Cu^II, the initial act of complexing involves destruction of the Co^II and Cu^II hexacyanoferrates(II) by OH^– ions, leading to formation of the corresponding hydroxides which react with the ligand indicated. In the both systems, successive addition of two ligand molecules per M(OH)₂ fragment occurs and [MB(OH)(OH₂)] and [MB₂] coordination compounds are formed (B^–-a singly deprotonated ligand form). In the Ni^II-N-diisopropoxythiophosphorylthiobenzamide system, the formation of three complexes, (Ni₂BOH)₂[Fe(CN)₆], [NiB(OH)(OH₂)] and [NiB₂] occurs.     

Studies on 2-acetylthiophene-2-furoylhydrazone complexes of 3d-bivalent metal ions

Summary Metal(II) complexes of 2-acetylthiophene-2-furoylhydrazone (HL) of the types [VO(HL)SO₄], [Cu(HL)₂Cl₂(H₂O)], [M(HL)₂Cl₂] [M=Co^II, Ni^II, or Zn^II] and [ML₂(H₂O)₂] [M=Co^II, Ni^II, Cu^II or Zn^II] have been prepared and characterized on the basis of elemental analyses, molar conductance, magnetic susceptibility, visible, e.s.r. and i.r. spectral studies. The bonding and stereochemistry of the complexes are discussed.     

Azidocuprate(II). Die Kristallstruktur von (PPh4)2[Cu2(N3)6]

Azidocuprates(II). Crystal Structure of (PPh₄)₂[Cu₂(N₃)₆] (PPh₄)₂[Cu(N₃)₄] and (PPh₄)₂[Cu₂(N₃)₆], which is already known, are prepared from the corresponding chloro cuprates and excess silver azide in dichloro methane suspension. The azido cuprates form nonexplosive brown crystals of low sensitivity to moisture and are characterized by i.r. spectroscopy. (PPh₄)₂[Cu₂(N₃)₆] was submitted to a X-ray crystallographic structural analysis (4284 observed, independent reflexions, R = 0.034). The compound crystallizes triclinic in the space group P1 with one formula unit per unit cell. The lattice parameters are a = 1047.4 pm; b = 1131.1 pm; c = 1179.4 pm; α = 101.26°; β = 109.31°; γ = 103.42°. The compound consists of PPh₄^⊕ cations and centrosymmetric anions [Cu₂(N₃)₆]^2?, which meet D_2h-symmetry fairly well. In the anions the copper atoms are linked to a planar Cu₂N₂ four-membered ring by the N α atoms of two azide groups. The other azido ligands are bonded terminally and complete coordination number 4 at the Cu atoms which show planar geometry.     

ZnII and CuII complexes generated from 5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione

A new 1,3,4‐oxadiazole‐containing bispyridyl ligand, namely 5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione (L), has been used to create the novel complexes tetranitratobis{μ‐5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione}zinc(II), [Zn₂(NO₃)₄(C₁₄H₁₂N₄OS)₂], (I), and catena‐poly[[[dinitratocopper(II)]‐bis{μ‐5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione}] nitrate acetonitrile sesquisolvate dichloromethane sesquisolvate], {[Cu(NO₃)(C₁₄H₁₂N₄OS)₂]NO₃·1.5CH₃CN·1.5CH₂Cl₂}_n, (II). Compound (I) presents a distorted rectangular centrosymmetric Zn₂L₂ ring (dimensions 9.56 × 7.06 Å), where each Zn^II centre lies in a {ZnN₂O₄} coordination environment. These binuclear zinc metallocycles are linked into a two‐dimensional network through nonclassical C—H...O hydrogen bonds. The resulting sheets lie parallel to the ac plane. Compound (II), which crystallizes as a nonmerohedral twin, is a coordination polymer with double chains of Cu^II centres linked by bridging L ligands, propagating parallel to the crystallographic a axis. The Cu^II centres adopt a distorted square‐pyramidal CuN₄O coordination environment with apical O atoms. The chains in (II) are interlinked via two kinds of π–π stacking interactions along [01]. In addition, the structure of (II) contains channels parallel to the crystallographic a direction. The guest components in these channels consist of dichloromethane and acetonitrile solvent molecules and uncoordinated nitrate anions.     

Poly[tetraamminecopper(II) bis[tris(μ2‐cyanido‐κ2C,N)dicuprate(I)]]: a unique CuI–CuII mixed‐valence complex containing anionic cuprous cyanide layers and [Cu(NH3)4]2+ cations

The title compound, {[Cu(NH₃)₄][Cu(CN)₃]₂}_n, features a Cu^I–Cu^II mixed‐valence CuCN framework based on {[Cu₂(CN)₃]⁻}_n anionic layers and [Cu(NH₃)₄]²⁺ cations. The asymmetric unit contains two different Cu^I ions and one Cu^II ion which lies on a centre of inversion. Each Cu^I ion is coordinated to three cyanide ligands with a distorted trigonal–planar geometry, while the Cu^II ion is ligated by four ammine ligands, with a distorted square‐planar coordination geometry. The interlinkage between Cu^I ions and cyanide bridges produces a honeycomb‐like {[Cu₂(CN)₃]⁻}_n anionic layer containing 18‐membered planar [Cu(CN)]₆ metallocycles. A [Cu(NH₃)₄]²⁺ cation fills each metallocyclic cavity within pairs of exactly superimposed {[Cu₂(CN)₃]⁻}_n anionic layers, but there are no cations between the layers of adjacent pairs, which are offset. Pairs of N—H...N hydrogen‐bonding interactions link the N—H groups of the ammine ligands to the N atoms of cyanide ligands.     

Tetraoxotetraamide macrocyclic complexes

A new class of 16- and 17-membered tetraamide macrocyclic complexes, [ML¹X₂] and [ML²X₂] [M = Mn^II, Co^II, Ni^II, Cu^II or Zn^II; X = NO₃ or Cl], have been prepared by the template reaction of anthranilic acid, 1,2-diaminoethane or 1,3-diaminopropane and succinic acid in 2:1:1 molar ratio. The stoichiometries and coordination modes of the complexes have been deduced from physicochemical and spectroscopic measurements. This revised version was published online in June 2006 with corrections to the Cover Date.     

Bis(N-octylsalicylideniminato-N,O)copper(II)

In the title compound, [Cu(C₁₅H₂₂NO)₂], the Cu^II cation lies on a centre of symmetry. The coordination geometry about the Cu^II ion is a parallelogram, formed by the N₂O₂ donor set of the two bidentate long alkane chain Schiff base imine–phenol ligands. The Cu—N and Cu—O distances are 2.009 (3) and 1.888 (3) Å, respectively.     

Metal(II) complexes and metal(II) salts ofN-carbamoylpyrazole: N,O and N,N coordination

Summary Several new coordination compounds are reported withN-carbamoylpyrazole (Hcpz) as the ligand;viz. M(cpz)₂ where M = Cu^II and Ni^II; M(Hcpz)Cl₂ where M = Mn^II, Co^II, Cu^II, Zn^II and Cd^II; M(Hcpz)₂Cl₂ Where M = Fe^II, Co^II and Ni^II: M(Hcpz)₃(BF₄)₂ where M = Fe^II, Co^II, Ni^II, Zn^II and Cd^II; and Cu(Hcpz)₂(BF₄)₂. In the salts, Hcpz is coordinated through the nitrogen atoms of the pyrazole ring and the nitrogen atom of the carbamoyl group. In the Hcpz complexes, coordination takes place through the nitrogen atom of the pyrazole ring and the oxygen atom of the carbamoyl group.     

The coordination chemistry ofN,N′-ethylenebis(2-acetylpyridine imine) andN,N′-ethylenebis(2-benzoylpyridine imine); two potentially tetradentate ligands containing four nitrogen atoms

Summary New complexes of the general formulae [ML_A(H₂O)₂]-Cl₂ (M=Ni or Cu), [ML_AX₂] (M=Co or Cu; X=Cl or Br), [NiL_ABr₂]·H₂O, [ML_A] [MCl₄] (M=Pd or Pt), [NiL_B(H₂O)₂]Cl₂·2H₂O, [ML_BCl₂] (M=Co, Ni, Cu, Pd or Pt; X=Cl or Br) and [ML_B] [MCl₄] (M=Pd or Pt), where L_A=N,N-ethylenebis(2-acetylpyridine imine) and L_B=N, N-ethylenebis(2-benzoylpyridine imine), have been isolated. The complexes were characterized by elemental analyses, conductivity measurements, t.g./d.t.g. methods, magnetic susceptibilities and spectroscopic (i.r., far-i.r., ligand field,¹Hn.m.r.) studies. Monomeric pseudo-octahedral stereochemistries for the Co^II, Ni^II and Cu^II complexes andcis square planar structures for the compounds [ML_BX₂] (M=Pd or Pt; X=Cl or Br) are assigned in the solid state. The molecules L_A and L_B behave as tetradentate chelate ligands in the Co^II, Ni^II, Cu^II and Magnus-type Pd^II and Pt^II complexes, bonding through both the pyridine and methine nitrogen atoms. A bidentateN-methine coordination of the Schiff base L_B is assigned in the [ML_BX₂] complexes (M=Pd or Pt; X=Cl or Br). The anomalous magnetic moment values of the Co^II complexes are discussed.     

The weakly coordinating perchlorate group in bis(N,N′‐dimethylethylenediamine‐κ2N,N′)bis(perchlorato‐κO)copper(II) studied at 100, 250 and 400 K

The crystal structure of the title compound, [Cu(ClO₄)₂(C₄H₁₂N₂)₂], (I), is reported at 100, 250 and 400 K. The Cu^II cation in this complex is coordinated in a distorted octahedral mode characteristic of Jahn–Teller systems. The coordination of the perchlorate ligands via longer, and presumably weaker, axial Cu—O distances varies significantly as a function of temperature. One of the Cu—O distances increases between 100 and 250 K, and one of the Cu—O—Cl angles expands between 250 and 400 K. At all temperatures, the complex forms a two‐dimensional N—H...O hydrogen‐bond network in the (001) plane.