The thermal decomposition of transition-metal complexes containing heterocyclic ligands: 3. Substituted pyridine complexes of cobalt

Enthalpies of the overall decomposition reactions CoX₂L₂(c) → CoX₂(c)+2L(g) and of the intermediate stepwise loss of ligand, L, where X is Cl or Br, and L is 3-chloropyridine, 3-bromopyridine, 2-chloropyridine, 2-bromopyridine, or 2-methoxypyridine have been measured by use of a differential scanning calorimeter. Enthalpies of sublimation of CoCl₂(3-chloropyridine)₂, CoBr₂(3-chloropyridine)₂, CoCl₂(3-bromopyridine)₂, CoCl₂(2-chloropyridine)₂, CoCl₂(2-bromopyridine)₂, CoBr₂(2-bromopyridine)₂, CoCl₂(2-methylpyridine)₂ and CoBr₂(2-methylpyridine)₂ have been determined. Values of the cobalt-nitrogen bond dissociation energies have been calculated. Specific heats of a number of the complexes are reported.     

The thermal decomposition of transition-metal complexes containing heterocyclic ligands: I. Benzothiazole complexes

Enthalpies of the decomposition reactions MX₂L₂(c)→MX₂(c) + 2L (g), where M is Mn, Co, Ni, Cu, or Cd, X is Cl and/or Br, and L is benzothiazole or 2-methyl-benzothiazole have been measured by use of a differential scanning calorimeter. Specific heats and enthalpies of sublimation of some of the complexes have been obtained.     

Synergic effect of palladium-based bimetallic catalysts for the hydrogenation of nitroaromatics

Bimetallic catalysts, PdCl₂-MX_n and PdCl₂(PhCN)₂-Mx_n (MX_n=FeCl₃, Fe(acac)₃, Co(OAc)₂, CoCl₂, Co(acac)₂, NiCl₂, Ni(OAc)₂, RuCl₃, Cu(OAc)₂, CuCl₂), exhibit remarkable synergic effect which can obviously increase the activity of the monometallic Pd catalyst for the hydrogenation of nitroaromatics, whereas MX_n alone is not catalytically active under the same reaction conditions.     

The preparation and spectral properties of the new ‘mixed’ complexes [MI2(CO)3(py)L] (M = Mo and W; L = PPh3, AsPh3 and SbPh3)

Abstract

Seven-coordinate complexes of molybdenum(II) and tungsten(II) have become increasingly important as homogeneous catalysts. For example, the complexes [MX₂(CO)₃L₂] (M = Mo and W; X = Cl and Br; L = PPh₃ and AsPh₃) have been shown to be catalysts for the ring-opening polymerisation of norbornene.¹ Although a wide variety of complexes of the type [MX₂(CO)₃L₂] (M = Mo and W; X = Cl, Br and I; L = nitrogen, phosphorus, arsenic and antimony donor ligands)² have been reported, until now no examples of the mixed complexes [MX₂(CO)₃(py)L] have been prepared. In this communication we wish to describe the synthesis of the new mixed pyridine/L compounds [MI₂(CO)₃(py)L] (M = Mo and W; L = PPh₃, AsPh₃ and SbPh₃).     

Preface

Abstract

The FT-IR and Raman spectra of eight new complexes of formula ML₂Ni(CN)₄ (where M = Mn, Fe, Co, Ni, Cu or Cd and L = 2-chloropyridine; M = Ni or Cd and L = 2-bromopyridine) are reported. The spectroscopic results indicate that the complexes have structures consisting of corrugated polymeric layers of [M-Ni(CN)₄]∞ with 2-substituted pyridine molecules bound directly to the metal (M). For a given ligand (2-Clpy or 2-Brpy) the effects of metal-ligand bond formation on the ligand modes are examined. Metal-ligand bond strengths of the halo-derivatives of pyridine (L = 2-Clpy or 2-Brpy), inferred by the effects on frequency shifts of certain ligand modes, have also been compared.     

New Gilman-type lithium cuprate from a copper(II) salt: synthesis and deprotonative cupration of aromatics

Deprotonative cupration of aromatics including heterocycles (anisole, 1,4-dimethoxybenzene, thiophene, furan, 2-fluoropyridine, 2-chloropyridine, 2-bromopyridine, and 2,4-dimethoxypyrimidine) was realized in tetrahydrofuran at room temperature using the Gilman-type amido-cuprate (TMP)₂CuLi in situ prepared from CuCl₂·TMEDA through successive addition of 1 equiv of butyllithium and 2 equiv of LiTMP. The intermediate lithium (hetero)arylcuprates were evidenced by trapping with iodine, allyl bromide, methyl iodide, and benzoyl chlorides, the latter giving the best results. Symmetrical dimers were also prepared from lithium azine and diazine cuprates using nitrobenzene as an oxidative agent.     

Coordination compounds of ethylhydrazine and 2,2,2-Trifluoroethylhydrazine; crystal and molecular structure of dichlorotetrakis(2,2,2-Trifluoroethylhydrazine) nickel(II)

Ethylhydrazine (EH) forms the complexes MX₂(EH)₂ (M = Co, Ni; X = Cl; M = Co, X = Br), NiBr₂(EH)₂(H₂O) and MX₂(EH) (M = Zn, Cd; X = Cl; M = Zn, X = Br). Spectroscopic evidence suggests that these all contain bridging hydrazine ligands, the cobalt and nickel complexes containing six coordinated metal atoms while the zinc and cadmium complexes are tetrahedral. 2,2,2-Trifluoroethylhydrazine (TFEH) in contrast, forms six coordinate complexes of the type MX₂(TFEH)₄ (M = Co, Zn, X = Br; M = Co, Ni, X = NCS; M = Ni, X = Cl) for which spectroscopic evidence points to unidentate coordination by the hydrazine. An X-ray crystal structure determination on NiCl₂(TFEH)₄ confirms that the hydrazine bonds to nickel through the NH₂ nitrogen only, in a tetragonal structure with axial chlorine atoms. One bis(TFEH) complex ZnBr₂(TFEH)₂ and one hexakis (TFEH) complex, NiBr₂(TFEH)₆, have also been isolated.     

Nucleophilic substitution of halopyridines by benzenethiolate anion via a radical chain mechanism

2-Halopyridines 1a-d reacted with sodium thiophenoxide in DMF at 80° to afford the ipso-substitution products. The following relative order of reactivity was observed: 2-iodopyridine ( 1a) ∼ 2-bromopyridine ( 1b) ≫ 2-chloropyridine ( 1c ) ∼ 2-fluoropyridine ( 1d ). The reaction of 1b is inhibited by the electron scavenger azobenzene and by the radical scavenger benzoqoquinone. Furthermore, results of the reaction of 3-bromopyridine ( 2b ) serve to rule out pyridyne mechanism. It is reasonable to suggest therefore that the reaction proceeds through the radical chain process containing one electron transfer, that is S_RN1.     

Synthesis and characterization of (pyrazolylethylphosphinite)nickel(II) complexes and catalytic activity towards ethylene oligomerization

Compounds (2‐(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)ethyldiphenylphosphinite ( L1 ), 2‐(3,5‐di‐tert‐butyl‐1H‐pyrazol‐1‐yl)ethyldiphenylphosphinite ( L2 ) , and 2‐(3,5‐diphenyl‐1H‐pyrazol‐1‐yl)ethyldiphenylphosphinite ( L3 ) were prepared using the synthetic routes reported in literature. These compounds were reacted with [NiCl₂(DME)₂] or [NiBr₂(DME)₂] under appropriate reaction conditions to afford six new nickel(II) compounds ([NiCl₂( L1)] ( 1 ), [NiCl₂( L2 )] ( 2 ), [NiCl₂( L3 )] ( 3 ), [NiBr₂( L1 )] ( 4 ), [NiBr₂( L2 )] ( 5 ) and [NiBr₂( L3 )] ( 6 )). The new nickel(II) pre‐catalysts catalyze the oligomerization of ethylene, in the presence of ethylaluminium dichloride as co‐catalyst, to produce butenes, hexenes, octenes and higher carbon chain ethylene oligomers with very little Friedel‐Crafts alkylation products when the reactions were run in toluene.     

Verdampfung von Kupfer(II)chlorid und Struktur des Dampfes untersucht mit UV./VIS.- und Raman-Spektroskopie

The vapour pressure of CuCl₂ and the dimerization of CuCl₂(g) have been investigated by optical spectroscopy in the range 420–650°C, p = 0.5-5 atm. The enthalpy of dimerization of CuCl₂(g) was determined by visible and by Raman spectroscopy and good agreement was found (?154 kJmol^?1 and ?143 kJmol^?1). CuCl₂(g) shows two totally symmetric Raman modes (373 and 127 cm^?1) indicating that, at least at elevated temperatures, CuCl₂(g) is not a linear molecule. The optical spectra of Cu₂Cl₄(g) and CuLCl₅(g) (L ? Ga, In) are very similar supporting a CuCl₃-chromophor in both cases. The formerly proposed structure of CuL₂Cl₈(g) (L ? Al, Ga) contains bridging and terminal chlorides, structural elements also present in Cu₂Cl₄(g). In agreement with the proposed structure v is identical in Cu₂Cl₄(g) and CuL₂Cl₈(g), while V is at lower energies (20–30 cm^?1) in CuL₂Cl₈(g) than in Cu₂Cl₄(g).     

New nickel(II) chloride-morpholine complexes

The compounds [NiCl₂(Morph)₃(H₂O)₂] and [NiCl₂(Morph)₃] have been prepared by treating NiCl₂·6H₂O with morpholine (Mo     

Co-ordination compounds of glyoxal bis(dimethylhydrazone)

Complexes derived from glyoxal bis(dimethylhydrazone) (GDMH) have been prepared and characterised; they are of the general types MX₂(GDMH) (M  Co, Zn, Cd; X  Cl, Br and M  Zn, X  SCN) and MX₂(GDMH)₂ (M  Co, Ni; X  SCN). In all the complexes the ligand is chelating;MX₂(GDMH) are tetrahedral monomers while MX₂(GDMH)₂ contain six co-ordinated metal atoms. The ligand is monoprotonated in mineral acids and the salts [GDMH₂][CoBr₄] and [GDMH₂]PdBr₄ have been isolated from acidic solution.     

Evaluation of the antimicrobial activity of some chloro complexes of imidazole-2-carbaldehyde semicarbazone: X-ray crystal structure of cis-NiCl2(H2L)(H2O)

Some first row transition metal(II) complexes of imidazole-2-carbaldehyde semicarbazone (H₂L) have been synthesised and characterised. Single crystal X-ray diffraction studies have revealed the molecular structure of the neutral complex NiCl₂(H₂L)(H₂O). This latter complex shows a pseudo-octahedral geometry, with both chloride ions displaying a cis disposition. The asymmetry of this complex allows the formation of two enantiomers in the racemic crystal structure. The non-deprotonated semicarbazone ligand behaves as an N,N,O-donor, through the imidazole and imine N atoms and the O_keto atom. The coordinative behaviour of H₂L in CuCl₂(H₂L)(H₂O), ZnCl₂(H₂L)₂·0.5EtOH and CoCl₂(H₂L)₂·0.5H₂O is reported as only N,O-donor. The antimicrobial activity of the semicarbazone ligand and its metal complexes has been tested against some representative bacteria and fungi. A moderate inhibitory activity of the cobalt complex was detected towards the assayed phytopathogenic fungi Alternariatenuis and Sclerotinia minor (MIC 50 μg/mL).     

Thermodynamic properties of transition metals in aqueous solution: 1. The enthalpies of dilution of some aqueous transition metal chloride solutions at 25°C

Enthalpies of dilution H _D of aqueous solutions of the transition metal chlorides CdCl₂, CoCl₂, CuCl₂, MnCl₂, and NiCl₂ were measured from 1.0 molal to dilute solution at 25°C. The apparent molal enthalpy equations of Pitzer were then fit to the resulting H _D data and the parameters for these equations are presented. The heat of dilution data for CdCl₂ and CuCl₂ were in good agreement with results by other workers.     

Cobalt(II), nickel(II), copper(II) and copper(I) complexes of 2-mercapto-5-methyl-1,3,4-thiadiazole and 2,5-bis(methylmercapto)-1,3,4-thiadiazole

Summary Some cobalt(II), nickel(II), copper(II) and copper(I) complexes of 2-mercapto-5-methyl-1,3,4-thiadiazole (mttz) and 2,5-bis(methylmercapto)-1,3,4-thiadiazole (bmttz) have been prepared and studied by conductometric and magnetochemical methods and by electronic and i. r. spectroscopy. The complexes CoX₂ · 2L (L=mttz, X=Cl, Br or I; L=bmttz, X=Br or I), CoCl₂ · bmttz are pseudotetrahedral, and the complexes NiX₂ · mttz (X=Cl or Br), NiCl₂ · 1.3 bmttz, NiBr₂ · 1.5 bmttz are pseudooctahedral. The complex Co₃(OAc)₂ · 4(mttz-H) · 2H₂O has an undefinite constitution. The polynuclear complexes CuCl₂ · 1.3 mttz and CuBr₂ · 1.2 mttz contain presumably pseudotetrahedral chromophores, the chloride having a subnormal magnetic moment. The CuX₂ · 2 bmttz (X=Cl, Br or NO₃) complexes have a six coordination with bridging ligand molecules. In the CuX · 2 mttz (X=Cl, Br or ClO₄) complexes the anions are coordinated, while in the CuClO₄ · 2 bmttz complex the perchlorate anion is ionically bonded.     

Bestimmung von freier Essigs?ure neben Metallsalzen durch automatische Acidimetrie

Zusammenfassung Bei Verwendung einer automatisch arbeitenden potentiometrischen Apparatur (Titrator TTT 1c + Titrigraph SBR 2c, Radiometer) kann freie Essigsäure in Anwesenheit von Metallsalzen mit ausreichender Genauigkeit zur Untersuchung von Essigsäuresolvaten, wie z. B. NiCl₂·0,5 CH₃COOH, CuCl₂·0,5 CH₃COOH, PbCl(CH₃COO)·CH₃COOH, bestimmt werden.

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Summary Using an automatically working potentiometric apparatus (Titrator TTT 1c + Titrigraph SBR 2c, Radiometer) free acetic acid can be determined in presence of metal salts with sufficient exactness to analyze acetic acid solvates, i.e. NiCl₂·0.5 CH₃COOH, CuCl₂·0.5 CH₃COOH, PbCl(CH₃COO)·CH₃COOH.

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Die Verfasser danken der Deutschen Forschungsgemeinschaft und der Wissenschaftlichen Gesellschaft des Saarlandes e.V. für die Förderung dieser Untersuchungen durch Sachmittel.     

The thermal decomposition of transition-metal complexes containing heterocyclic ligands: 2.Benzoxazole complexes

Enthalpies of the overall decomposition reactions

and of the intermediate reactions involving stepwise loss of ligand, L, where M is Mn, Co, Ni, Cu, or Cd, X is Cl or Br, and L is benzoxazole, 2-methylbenzoxazole, or 2,5-dimethylbenzoxazole have been measured by use of a differential scanning calorimeter. Specific heats of CoCl₂(2-methylbenzoxazole)₂, and CoBr₂(2-methylbenzoxazole)₂ are reported together with enthalpies of sublimation of CoCl₂(2-methylbenzoxazole)₂, CoBr₂(2-methyl-benzoxazole)₂, CoCl₂(2,5-dimethylbenzoxazole)₂ and CoBr₂(2,5-dimethylbenzoxazole)₂. Enthalpies of decomposition of benzoxazole complexes are found to be greater than those of the corresponding pyridine complexes, but less than those of the analogous benzothiazole complexes. However, the mean bond dissociation energies of the cobalt—nitrogen and cobalt—oxygen bonds in these complexes are all in the region 33±2 kcal mol^?.     

The synthesis and characterization of a new (E,E)-dioxime containing 18-membered dithiadiazadioxamacrocyclic moieties and its mononuclear complexes

A new (E,E)-dioxime, (21Z,22Z)-6,7,9,10,12,13-hexahydro-16H- benzo[h][1,4,7,16,10,13][1, 4,7,16,10,13]dioxadithiadiazacyclooctadecine-21,22(20H,23H)-dione dioxime (H ₂ L) has been synthesized by reacting cyanogen-di-N-oxide (2) with (2-{[2-(2-{2-[(7-aminocyclohepta-1,4,6-trien-1-yl)thio]ethoxy}ethoxy)ethyl]thio}phenyl)amine. Mononuclear complexes of this ligand have been synthesized by reacting the vic-dioxime (H₂L) with CuCl₂, NiCl₂.6H₂O and CoCl₂.6H₂O respectively. The BF₂⁺ capped Ni(II) and Co(III) complexes of the dioxime have been synthesized from. The new compounds were characterized by a combination of elemental analysis, ¹H- and ¹³C-n.m.r, I.R. and m.s. spectral data.     

Contacted Ion Pairs in Aqueous CuCl2 by the Combination of Ratio Spectra,Difference Spectra,Second Order Difference Spectra in the UV-Visible Spectra

The microstructure of aqueous CuCl₂ has been studied through lots of technologies for many years; however, it remains a controversial subject. In this study, a new spectroscopic method has been proposed to analyze the UV-visible spectra of thin film of CuCl₂/H₂O solutions at different concentrations. This method is the combination of ratio spectra, difference spectra and second order difference spectra. By using this method, two new bands at ~230 and ~380 nm are obviously observed. The bands are assigned as the contacted ion pairs[CuCl₃(H₂O)_n]^- or[CuCl₄(H₂O)_n]^2-, which demonstrates that ion pairs exist in the CuCl₂/H₂O solution. Such finding agrees with the recent theoretical spectra obtained by time-dependent density functional theory. Furthermore, the populations of the contacted ion pairs are discussed. This study not only offers the direct spectroscopic evidence of[CuCl₃(H₂O)_n]^- or[CuCl₄(H₂O)_n]^2- in aqueous CuCl₂, but also suggests that the spectroscopic analysis method is powerful to extract the weak bands in a strong overlapping spectrum.     

Über 1,2-Phenylenoxothio-3d-Element-Verbindungen

On 1,2-Phenyleneoxothio 3d-Element Compounds MnCl₂, NiCl₂, CoCl₂, and CuCl₂ react with o-mercaptophenol in molar ratio 1:1 in methanol in presence of stoichiometric amounts of triethylamine giving the methanol adducts of 1, 2-phenyleneoxothio-3d-element compounds. By ligand exchange reactions the amine complexes are accessible. Ligand-free 1, 2-phenyleneoxothio-3d-element compounds are described too. The magnetic, spectroscopic, and thermal behaviours of these compounds have been investigated.