Vanadium chemistry of o-mercaptophenol. Part IV. Construction of heterobinuclear complexes via the synthon [V(mp)3]2− (mp = o-mercaptophenolato dianion). Syntheses and structures of (BzMe3N)2[V(mp)3] · MeCN · 1/2 MeOH and V–Co complexes

The mononuclear complex (BzMe₃N)₂[V(mp)₃] · MeCN · 1/2 MeOH (1) (mp = o-SC₆H₄O^2–) obtained by reacting VCl₃ with Na₂mp in the presence of BzMe₃NBr contains the synthon [V(mp)₃]^2–. Further reaction with Co₂(CO)₈ gave [V(mp)₃Co(Py)2(MeCN)] · 2MeCN (2) and [V(mp)₃Co(DMF)₃] (3), depending on the recrystallization conditions. The coordination geometry of the V atoms in all these complexes lies between an octahedron and a trigonal prism. Upon formation of (2) and (3), the terminal oxo atoms of mp become 2-O bridges between V and Co, while the latter atom is also octahedral.     

Thermal properties of ternary systems: The calculation of the standard enthalpy of solution for compounds in binary mixtures

An equation free of fitting parameters is proposed for calculating the standard heats of solution for compounds in nonaqueous binary mixtures. The parameters of the equation are the standard heats of solution of a compound in the components of the mixed solvent. Nonlinear ΔH ⁰(x) trends are reconstructed for solutions of water in i-PrOH + MeOH and MeCN + MeOH, t-BuOH in MeCN + MeOH, squalane in CHCl₃ + CCl₄ and C₆H₆ + CHCl₃, and hexadecane in MeOH + i-Pr₂O and in mixtures of butyl acetate, ethyl acetate, and 1,4-dioxane with 1-octanol. The standard heats of solutions are calculated for water in alcohol + alcohol, alcohol + aprotic solvent, and aprotic solvent + aprotic solvent mixtures     

The preparation and characterization of mono- and bis-chelated cadmium(II) complexes of the di-2-pyridylketone Schiff base of S-methyldithiocarbazate (Hdpksme) and the X-ray crystal structure of the [Cd(dpksme)2] · 0.5 MeOH complex

New cadmium(II) complexes of empirical formulae, [Cd(dpksme)X] (dpksme = anionic form of the Schiff base; X = NCS^–, Cl^–, I^–) and [Cd(dpksme)₂] · 0.5MeOH, respectively have been prepared and characterized. The mono-ligated cadmium(II) complexes, [Cd(dpksme)X] are four-coordinate and tetrahedral but the bis-ligand complex, [Cd(dpksme)₂] · 0.5MeOH is six-coordinate and octahedral. The crystal and molecular structure of [Cd(dpksme)₂] · 0.5MeOH has been determined by X-ray diffraction. The complex has a distorted mer-octahedral structure in which the ligands are coordinated as uninegatively charged tridentate chelating agents via the pyridine nitrogen atoms, the azomethine nitrogen atoms and the thiolate sulfur atoms. The distortion from regular octahedral geometry is ascribed to the restricted bite angles of the ligands. The Schiff base and its cadmium(II) complexes exhibit mild antibacterial activities against Shigella dysenteriae, Bacillus cereus, Staphylococcus aureus and Escherichia coli. They are also mildly fungitoxic against the phytopathogenic fungi, Alternaria alternata and Macrophomina phaseolina.     

Seven-coordinate rhenium(III) complexes of 1-(2-pyridylazo)-2-naphtholate: X-ray studies,spectroscopic characterization and DFT calculations

The reactions of [ReX₃(MeCN)(PPh₃)₂] (X = Cl or Br) with 1-(2-pyridylazo)-2-naphthol (HPAN) have been examined and the [ReBr(PAN)₂] · 2CHCl₃ (1) and [ReCl(PAN)₂] (2) complexes have been obtained. The both complexes have been structurally and spectroscopically characterized, and compound 1 has been additionally studied by magnetic measurements. The magnetic behavior is characteristic of mononuclear seven-coordinated Re(III) complex with d⁴ low-spin configuration, which gives diamagnetic ground state.     

Redox reactions involving rhenium and uranium hexafluorides,a convenient synthesis of β-uranium pentafluoride

Rhenium and uranium hexafluorides oxidise elemental iodine in iodine pentafluoride at ambient temperature to give the I₂⁺ cation. With UF₆ an additional reaction occurs to give β-uranium pentafluoride as one product, β-UF₅ is soluble in acetonitrile without disproportionation and is also formed from the reduction of UF₆ by MeCN. Copper, cadmium, and thallium metals are oxidised by ReF₆ in MeCN giving Cu^I, Cd^II, and Tl^I hexafluororhenates(V) but the reactions are complicated by reaction between ReF₆ and the solvent.     

Copper(II)-Mediated Iodination of 1-Nitroso-2-naphthol

The 3-Iodo-1-nitrosonaphthalene-2-ol (I-NON) was obtained by the copper(II)-mediated iodination of 1-nitroso-2-naphthol (NON). The suitable reactants and optimized reaction conditions, providing 94% NMR yield of I-NON, included the usage of Cu(OAc)₂·H₂O and 1:2:8 Cu^II/NON/I₂ molar ratio between the reactants. The obtained I-NON was characterized by elemental analyses (C, H, N), high-resolution ESI⁺-MS, ¹H and ¹³C{¹H} NMR, FTIR, UV-vis spectroscopy, TGA, and X-ray crystallography (XRD). The copper(II) complexes bearing deprotonated I-NON were prepared as follows: cis-[Cu(I-NON–H)(I-NON)](I₃) (1) was obtained by the reaction between Cu(NON-H)₂ and I₂ in CHCl₃/MeOH, while trans-[Cu(I-NON–H)₂] (2) was synthesized from I-NON and Cu(OAc)₂ in MeOH. Crystals of trans-[Cu(I-NON–H)₂(THF)₂] (3) and trans-[Cu(I-NON–H)₂(Py)₂] (4) were precipitated from solutions of 2 in CHCl₃/THF and Py/CHCl₃/MeOH mixtures, respectively. The structures of 1 and 3–4 were additionally verified by X-ray crystallography. The characteristic feature of the structures of 1 and 3 is the presence of intermolecular halogen bonds with the involvement of the iodine center of the metal-bound deprotonated I-NON. The nature of the I···I and I···O contacts in the structures of 1 and 3, correspondingly, were studied theoretically at the DFT (PBE0-D3BJ) level using the QTAIM, ESP, ELF, NBO, and IGM methods.     

Transition metal complexes with thiosemicarbazide-based ligands,Part II,Synthesis and characterisation of nickel(II), cobalt(II), manganese(II) and zinc(II) complexes with the pentadentate ligand, 2,6-diacetylpyridine bis(S-methylisothiosemicarbazone)

Summary The reaction of warm alcoholic solutions of acetates of Co^II, Mn^II, Zn^II and Ni^II with 2, 6-diacetylpyridine andS-methylisothiosemicarbazide hydrogen iodide yielded the complexes: [Co(H₂L)I₂]·H₂O, [Mn(H₂L)(MeOH)₂]I₂, [Zn(H₂L)(MeOH)I]I and [Ni(HL)]I, (H₂L=the pentadentate pentaaza-ligand 2, 6-diacetylpyridine bis(S-methylisothiosemicarbazone)). The reaction of methanolic solutions of [Ni(HL)]I and NH₄NCS or LiOAc.2H₂O, give [Ni(HL)]NCS and NiL, respectively. For the complexes of Co^II, Mn^II and Zn^II, a pentagonal bipyramidal configuration is proposed, with H₂L in the equatorial plane and two unidentate ligands (I and/or MeOH) in the axial positions. The complexes [Ni(HL)]X (X=I or NCS) and NiL probably have monomeric five- and dimeric six-coordinate structures, respectively, in which only the chelate ligand is involved in coordination.     

Nickel(II) hexamethyleneiminedithiocarbamate complexes with triphenylphosphine or tributylphosphine

A series of square-planar nickel(II) hexamethylenedithiocarbamate complexes with heterogeneous coordination spheres of composition [NiX(hmidtc)Y] · nCHCl₃ [X = Cl, Br, I or NCS; hmi = C₆H₁₂, dtc = S₂CN^–; Y = PPh₃ or PBu₃, n = 0,1] have been synthesized and characterized by elemental analyses, i.r. and u.v.–v.i.s. spectroscopy, magnetochemical and conductivity measurements, and by thermal analysis. X-ray structures of [NiCl(hmidtc)(PPh₃)] · CHCl₃ and [NiBr(hmidtc)(PPh₃)] · CHCl₃ have been determined.     

Cyclic ligands with fixed coordination geometry. Part 7 Cationic copper(I) complexes of composition [Cu(Vn3S3)L]+-CF3SO 3 - (Vn3S3=5,10, 15-trithia-cyclo-triveratrylene,L=CO,CH3OH)

Summary Copper(I) trifluoromethanesulphonate and 5, 10, 15-trithia-cyclo-triveratrylene (Vn₃S₃, 3) react with CO in CHCl₃ as solvent to yield a carbonyl complex which can be crystallised from EtOH in a CO atmosphere giving the complex [Cu(Vn₃S₃)(CO)]O₃SCF₃·0.5 EtOH (8), which was characterised by av(CO) absorption band at 2140 cm^–1 indicating a weak back donation of copper(I). When (8) is heated in MeOH in an N₂ atmosphere, complex [Cu(Vn₃S₃)(CH₃OH)]O₃SCF₃·MeOH (15) is formed. X-ray analysis of (15) reveals a distorted tetrahedral coordination of the copper(I) ion with a strongly bonded methanol ligand (Cu–O 198 pm, Cu–S 229 pm).     

Crystal packing effects within [Mn3O] single-molecule magnets: Controlling intermolecular antiferromagnetic interactions

The reactions of 2-hydroxyphenylethanone oxime (Me-H₂salox) and (2-hydroxy-phenyl)-phenyl-methanone oxime (Ph-H₂salox) with Mn(ClO₄)₂·6H₂O in MeOH afford trinuclear manganese complexes of [Mn₃O(Me-salox)₃(MeOH)₃(ClO₄)]·MeOH (1·MeOH) and [Mn₃O(Ph-salox)₃(MeOH)₃(ClO₄)]·2MeOH (2·2MeOH), respectively. X-ray analysis shows that both complexes contain a manganese triangle core, [Mn^III₃O]⁷⁺. The structural distortion from the twisting of the oxime ligands dominates the ferromagnetic interactions within the three Mn ions in both compounds and results in an S = 6 ground state. The frequency dependence of out-of-phase signals in the alternating current (AC) magnetic susceptibility measurements and the temperature-dependent and sweep-rate-dependent hysteresis loops are indicative of single-molecule magnet behavior. Moreover, both complexes show step-wise magnetization, indicating the occurrence of quantum tunneling of magnetization (QTM). Interestingly, a tail to tail arrangement in the crystal packing of complex 1·MeOH results in strong intermolecular H-bonding interactions and leads to the exchange-bias effect from the antiferromagnetic interaction between the adjacent Mn₃ molecules. In contract, QTM steps of complex 2·2MeOH show an absence of the exchange-bias effect due to a weak intermolecular interaction from a head to tail arrangement.     

Heteroligand Cobalt(III) Complexes with Triethanolamine and Aminoacetic Acid

Heteroligand cobalt(III) chelates with triethanolamine and glycine, [Co(HTetm)GlyH₂O] · 2H₂O (I) and [Co(HTetm)GlyNH₃] · 2H₂O (II) (H₃Tetm is N(C₂H₄OH)₃ and HGly is glycine), were synthesized. The acidity constants of complex I were determined at an ionic strength of 0.1. The reactions of I with alcoholic solutions of acids, ammonia, and ammonium nitrate were studied. Binuclear complexes were obtained upon the interaction of I and II with CoCl₂ · 6H₂O. The complexes were characterized using UV–VIS (in aqueous and alcoholic solutions) and IR (in the solid state) spectroscopy. The ¹³C NMR spectra of solutions of Iand II were recorded. The plausible structures of the complexes are discussed.     

Can Serendipity Still Hold Any Surprises in the Coordination Chemistry of Mixed-Donor Macrocyclic ligands? The Case Study of Pyridine-Containing 12-Membered Macrocycles and Platinum Group Metal ions PdII,PtII, and RhIII

This study investigates the coordination chemistry of the tetradentate pyridine-containing 12-membered macrocycles L¹-L³ towards Platinum Group metal ions Pd^II, Pt^II, and Rh^III. The reactions between the chloride salts of these metal ions and the three ligands in MeCN/H₂O or MeOH/H₂O (1:1 v/v) are shown, and the isolated solid compounds are characterized, where possible, by mass spectroscopy and ¹H- and ¹³C-NMR spectroscopic measurements. Structural characterization of the 1:1 metal-to-ligand complexes [Pd(L¹)Cl]₂[Pd₂Cl₆], [Pt(L¹)Cl](BF₄), [Rh(L¹)Cl₂](PF₆), and [Rh(L³)Cl₂](BF₄)·MeCN shows the coordinated macrocyclic ligands adopting a folded conformation, and occupying four coordination sites of a distorted square-based pyramidal and octahedral coordination environment for the Pd^II/Pt^II, and Rh^III complexes, respectively. The remaining coordination site(s) are occupied by chlorido ligands. The reaction of L₃ with PtCl₂ in MeCN/H₂O gave by serendipity the complex [Pt(L³)(μ-1,3-MeCONH)PtCl(MeCN)](BF₄)₂·H₂O, in which two metal centers are bridged by an amidate ligand at a Pt1-Pt2 distance of 2.5798(3) Å and feature one square-planar and one octahedral coordination environment. Density Functional Theory (DFT) calculations, which utilize the broken symmetry approach (DFT-BS), indicate a singlet d⁸-d⁸ Pt^II-Pt^II ground-state nature for this compound, rather than the alleged d⁹-d⁷ Pt^I-Pt^III mixed-valence character reported for related dinuclear Pt-complexes.     

Influence of intermolecular hydrogen bonding on magnetic properties of mononuclear cobalt and nickel pivalates with amidine ligands

The magnetic properties of the mononuclear cobalt(ii) amidine complex Co(Me₃CCOO)₂{H₂N(C₅H₃N)NH(MeC=NH} (1) having a tetrahedral structure and its solvate 1·HOOCCMe₃·0.5C₆H₆ (1a) are substantially different. Complex 1 possesses ferromagnetic properties and exhibits residual magnetization at liquid-helium temperatures, whereas solvate 1a and the octahedral amidine complex Ni(Me₃CCOO)₂{H₂N(C₅H₃N)NH(MeC=NH}·MeCN (3·MeCN) show antiferromagnetic properties. Apparently, this is associated with the difference in the type of intermolecular nonbonded interactions in the crystals of 1, 1a, and 3·MeCN, which form channels for spin-spin exchange. The tetrahedral isostructural mononuclear complexes ML₂ (M = Co (5), Ni (6), L is N-tosyl-2,5-dimethyl-8-aminoquinoline) were synthesized. These complexes exhibit antiferromagnetic properties.     

Oxo-tricyano complexes of molybdenum(IV) with salicylaldehydehydrazone

[Mo(CN)₄O(H₂O)]^2– reacts with hydrazine and salicylaldehyde in aqueous solution to give [Mo(CN)₃O(salhy)]^2– (Hsalhy = salicylaldehydehydrazone), isolated as green (Ph₄P)₂[Mo(CN)₃O(salhy)] · 6H₂O. In CHCl₃, the product converts within seconds into (Ph₄P)₂[Mo(CN)₃O(salhy)] · H₂O · 2CHCl₃ yielding microcrystals having a metallic golden sheen. The complexes were characterised by elemental analysis, t.g. and d.t.a., u.v.–vis. absorption, i.r., ¹H-n.m.r. spectroscopy and by magnetic susceptibility measurements. The visible spectra in various solvents are dominated by the metal-to-ligand charge-transfer bands with absorption maxima linearly dependent on the Reichardt E _T parameter. In halogenated alkanes, the unusual hipsochromic band shift is interpreted in terms of possibile solvent bonding to the metal centre. Cyclic voltammetry indicates that the salt undergoes reversible one electron oxidation with E _1/2 = –0.473 V in DMSO versus ferrocene.     

Peripheral and non-peripheral-designed multifunctional phthalocyanines; synthesis, electrochemistry, spectroelectrochemistry and metal ion binding studies

A novel type of ionophore ligands, 3′-(2,3-dihydroxypropylthio)-phthalonitrile and 4′(2,3-dihydroxypropylthio)-phthalonitrile, and their α- and β-tetrasubstituted metallo phthalocyanines, (MPc), (M = Zn^II, Co^II, Mn^IIICl, Fe^IIIAc, Cu^II) have been prepared and fully characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR, and MS (ESI and Maldi-TOF). The complexes are soluble in both polar and non-polar solvents, such as MeOH and EtOH, THF, CHCl₃ and CH₂Cl₂. The spectroscopic properties of the complexes are affected strongly by the electron-donating sulfanyl units on the periphery of the phthalocyanines. The cation binding properties of the complexes, for example using Ag^I and Pd^II, were evaluated by UV-Vis spectroscopy and the results show the formation of polynuclear phthalocyanine complexes. Functional donors on the periphery of the zinc and copper complexes coordinate to Ag^I and Pd^II to give ca. a 2:1 metal-phthalocyanine complex binding ratio for the concentration of 2.5 × 10⁻⁵ M (Pc) and 1.0 × 10⁻³ M (Metal ions). Voltammetric and in-situ spectroelectrochemical studies were performed to characterize the redox behavior of the complexes. An in-situ electrocolorimetric method was applied to investigate the colors of the electro-generated anionic and cationic forms of the complexes.     

Novel tricarbonyl rhenium complexes of 5,8-quinolinedione derivatives - Synthesis, spectroscopic characterisation, X-ray structure and DFT calculations

The molecular structure of 7-acetamido-2-methyl-quinoline-5,8-dione has been determined and the reactivity of 7-acetamido-2-methyl-quinoline-5,8-dione (1) and 6-acetamido-2-methyl-quinoline-5,8-dione (2) towards Re(CO)₅Cl has been examined. Two novel tricarbonyl rhenium complexes, fac-[Re(CO)₃(7-acetamido-2-methyl-quinoline-5,8-dione)Cl]·CHCl₃ (3·CHCl₃) and fac-[Re(CO)₃(6-acetamido-2-methyl-quinoline-5,8-dione)Cl]₂·CHCl₃ (4·CHCl₃), have been synthesized and characterized spectroscopically and structurally. The electronic spectrum of 3 was investigated at the TDDFT level employing B3LYP functional in combination with LANL2DZ.     

Crystal Structure of Monoprotonated Ni(II) Nitrilotriacetate Tetrahydrate

A Ni(II) complex of the composition Ni(HNta) · 4H₂O (I) was synthesized. Its structure was found to consist of neutral mononuclear [Ni(HNta)(H₂O)₃] complexes and crystallization water molecules. The Ni atom has octahedral surrounding and is coordinated to tridentate-chelate HNta^2– ligand through the N atom and O atoms of two deprotonated acetate groups and through the O atoms of three water molecules. The structure of I was compared with those of the Zn(HNta) · 4H₂O and Co(HNta) · 4H₂O complexes isostructural to I. Thermogravimetric method showed that the decomposition of compound I occurs through several successive stages of dehydration, deaquation, decarboxylation, and the formation of inorganic residue.     

Synthesis,characterization and reactivity of thiolate-bridged cobalt-iron and ruthenium-iron complexes

Thiolate-bridged hetero-bimetallic complexes [Cp*M（Me CN）N₂S₂Fe Cl][PF₆]（2, M = Ru; 3, M = Co, Cp*= η⁵-C₅Me₅, N₂S₂= N,N’-dimethyl-3,6-diazanonane-1,8-dithiolate） were prepared by self-assembly of dimer [N₂S₂Fe]₂ with mononuclear precursor [Cp*Ru（MeCN）₃][PF₆] or [Cp*Co（Me CN）₃][PF₆]₂ in the presence of CHCl₃ as a...     

Cyclovoltammetric and spectroscopic characterization of optically active cobalt(II) and copper(II) complexes with the Schiff base derived from (N,N′)-(1R,2R)-(−)-cyclohexylenediamine and 2-hydroxyacetophenone

The Schiff base prepared by reacting (–)-(1R,2R)-1,2-cyclohexanediamine with 2-hydroxyacetophenone was used as a ligand for Co^II and Cu^II. The coordination compounds were studied by u.v.–vis. absorption and by circular dichroism (c.d.) spectroscopy in solution. The complexes are four-coordinated in a slightly distorted square planar symmetry. The distortion from planarity is a main factor influencing the chiral surroundings of the metal ion. The d–d and c.t. transitions are consistent with the observed distortion, which arises from intramolecular interactions between the methyl groups attached to the Schiff base imine carbon and hydrogen atoms of the cyclohexane ring. The electrochemical properties of the Co^II and Cu^II complexes were observed in MeCN but investigations revealed weaker oxygen activation than of Co^II analogue with salicylaldehyde. The Cu^II complex is reduced in H₂O to Cu^I which disproportionates to Cu^II and Cu⁰.     

Calorimetric study of phase transitions in the thiourea 1,1,2,2-tetrachloroethane clathrate compound

Heat capacities of the thiourea clathrate compound of 1,1,2,2-tetrachloroethane, {(NH₂)₂CS}₃(CHCl₂)₂, were measured at temperatures between 13 and 330 K. Two phase transitions were found. The enthalpy and entropy changes of the transition are 5940 J·mol^–1 and 28.1 JK^–1· mol^–1 for the one occurring at 224 K and 2756 J·mol^–1 and 11.3 JK^–1·mol^–1 for the other at 248 K. It is concluded from the transition entropy values that the guest molecules are orientionally disordered nearly to the same extent as in the neat liquid.Contribution No. 56 from the Microcalorimetry Research Center