Non-isothermal studies of adduct molecules of metallic halides with oxo-compounds in solid state.IV

Non-isothermal studies of some adduct molecules of metallic halides with di-isopropyl ether as the type MX₂(DIPE), in solid state, were carried out with a derivatograph, where M Mn(II), Co(II), Ni(II) or Cu(II), XCl^? or Br^?. DIPE  di-isopropyl ether and y = 0.2–1. These adduct molecules lost di-isopropyl ether in single or multiple steps upon heating. Thermally stable intermediate products were isolated and characterised by elemental analysis and IR spectral measurement. The activation energy for each step of decomposition of the adduct was evaluated from the analysis of TG, DTG and DTA curves of the respective derivatogram. The enthalpy change was evaluated from the DTA peak area and the order of reaction was found to be unity for each step of decomposition. Thermal parameters for the above adducts were compared with the adducts of other oxo-compounds like dioxan, tetrahydrofuran and ethylene glycol dimethyl ether.     

1H, 13C and 29Si NMR study of α- and β-silylstyrenes and their adducts with dichlorocarbene

¹H, ¹³C and ²⁹Si NMR spectra for the α- and β-silylstyrenes (E)-PhCHCHSiR₃ (I) and PhC(SiR₃)CH₂ (II) (R = Cl, Me, Ph), and those for some dichlorocarbene adducts of I and II (R = Me, Ph), were examined. From the ¹³C NMR data, the phenyl substituent in the molecules I and II enhances the electronic effects of the organosilicon substituent at Cα, and weakens these effects on the C_α resonance. The degree to which polarization of the vinyl CC bond is polarized increases with increased electron-withdrawing properties of substituent R in the SiR₃ group in compounds I and II, and correlates with the reduced reactivity of the bond toward electrophilic dichlorocarbene. Several long-range coupling constants (CC) in the molecules I, II and in their adducts with :CCl₂ were measured. The estimated CC is a useful aid for the study of electronic effects in organosilicon compounds.     

Ungesättigte silicium- und germaniumverbindungen: XVI. Stabilisierung des labilen silaethens Me2SiC(SiMe3)2 durch adduktbildung mit donoren. Reaktivität von Me2SiMe3)2 · NME3

Silaethene Me₂SiC(SiMe₃)₃ (1), unstable at −100°C with regard to dimerization, forms an adduct Me₂SiC(SiMe₃)₂ · NMe₃ (1 and NME, and can, therefore, serve as a source of 1. With 1 as an intermediate, the adduct 3 reacts with butadiene, cyclopentadiene, 2,3-dimethylbutadine, Ph₂CNSiMe₃, ^tBuN₃, isobutene or acetone giving either cycloadducts or ene reaction products. Adduct 3 reacts with ROH (R = H, Me, ^tBu, Ph) to yield insertion products, probably by way of a proton adduct of 3, but not via 1. Other donors (D) of which NMe₃ is an example form adducts 1 · D, producing a new class of silicon compounds. As the Lewis basicity of D, relative to 1, decreases (F⁻ ρ NMe₃ ρ NEt₃ ρ Br⁻ ρ THF), the resistance to decomposition of the adducts 1 · D to the dimer of 1 and D also decreases.     

Morpholine adducts of Co, Ni, and Mn benzoylacetonates: isostructurality and C–H···O hydrogen bonding

Morpholine adducts of nickel(II), cobalt(II), and manganese(II) benzoylacetonates, as well as a morpholine solvate of manganese(II) benzoylacetonate, were prepared and characterized by X-ray diffraction and thermal analysis. All four compounds crystallize in the P2₁/c space group with two complex molecules per unit cell. The morpholine solvate, along with the two adduct molecules, also contains four solvent morpholine molecules in the unit cell. The non-solvate compounds are isostructural, with crystal structures comprising 2D networks formed by C–H···O hydrogen bonding between phenyl rings and morpholine oxygen atoms. The topology of these networks can be described as intersecting C₂²(24) chains forming R₄⁴(48) rings. Networks with the same topology are also present in the solvate, but they are heavily distorted due to the presence of solvent morpholine molecules. Thermogravimetric analysis shows similar behavior of the non-solvate compounds upon thermal decomposition, with three degradation steps which can be related to gradual loss of morpholine molecules and subsequent overall decomposition. Decomposition of the solvate also proceeds in several steps, the first of which can be related to loss of solvent morpholine molecules and the further steps are analogous to those in the non-solvate compounds.     

Derivatographic studies on dehydration of salt hydrates and their deuterium oxide analogues. VI

Non-isothermal studies of the dehydration of double salt hydrates of the type K₂AB₄·M(II)SO₄·6H₂O where AB₄BeF^2?₄ or SeO^2?₄ and M(II)Mg(II), Co(II), Ni(II), Cu(II) or Zn(II) and their D₂O analogues were carried out. Thermal parameters like activation energy, order of reaction, enthalpy change, etc., for each step of dehydration were evaluated from the analysis of TG, DTA and DTG curves. These parameters were compared with the corresponding double sulphate, i.e., K₂SO₄·M(II)SO₄·6H₂O and their D₂O analogues. The role of divalent cation on the thermal properties of dehydration of the salt hydrates and also the effect on the thermal properties due to deuteration were discussed. The order of reaction was always found unity. The values of ΔH were within ～11-～19 kcal mol^?1     

Succinct Synthesis of Bosentan Utilizing Glycol Mono-THP Ether

A concise synthetic method for bosentan, a nonpeptide orally active dual endothelin (ET-1_A/B) receptor antagonist used for the treatment of pulmonary artery hypertension (PAH), was developed. We developed a new succinct synthetic route for bosentan by employing an acid-labile tetrahydropyran (THP)–protected glycol. THP group is advantageous over the previously known protection groups used in bosentan synthesis in that it provides a clean and quantitative deprotection. Bosentan was constructed via two parallel reaction pathways, yet the better product yield was obtained from a pathway via 6. Deprotection of THP ether was achieved under a mild acidic condition to afford bosentan.     

Derivatographic studies on dehydration of salt hydrates and their deuterium oxide analogues. III

Dehydration of double salt hydrates of the type M(I)₂SO₄·M(II)SO₄·6H₂O where M(I)Rb(I) and M(II)Mg(II), Mn(II), Co(II), Ni(II), Zn(II) and Cu(II) has been studied by derivatograph. Thermal parameters like activation energy, order of reaction, enthalpy change etc. for each step of dehydration have been evaluated from the analyses of TG, DTA and DTG curves and these parameters are compared with corresponding salt hydrates of the NH₄ and K(I) series. These double salt hydrates are deuterated and studied similarly. Activation energies for the first step of dehydration of these salt hydrates increase with the increase of second ionisation potential of the central metal except for Mg. The nature of dehydration changes in the cases of double salt hydrates of Mg(II) and Ni(II) on deuteration. The order of reaction for each case of dehydration has been found to be unity. The enthalpy change per mole of water varies from 11.4 to 17 kcal.     

Thermal Behaviour of Metal Complexes of 6-(2-Pyridylazo)-3-acetamidophenol

The present work aims chiefly to study the thermal behaviour of complex compounds with general formula: [M(HL)xH₂O](A)yH₂O (where HL=C₁₃H₁₁N₄O₂=6-(2-pyridylazo)-3-acetamidophenol (PAAP), M=Cu(II), Zn(II), Cd(II) and Fe(III) x=1, 3; y=2, 5) while A=CH₃COO^– (Ac), Cl₂. The second formula is [M(H₂L)xH₂O]Cl₂yH₂O, (where H ₂ L=C₁₃H₁₂N₄O₂ (PAAP), M=Ni(II), Co(II) x=3; y=4, 6). The compounds were identified by elemental analysis, FT-IR spectra and TG/DTG,DTA methods. It was found that during the thermal decomposition of complex compounds water molecules of crystallization are released in the first step. In the next step the pyrolysis of organic ligand takes place. Metal oxide remained as a solid product of the thermal decomposition. Mass spectroscopy has been used for the determination of the thermal decomposition on the intermediate products. It was found that the thermal stability of the studied compounds increases as the ionic radii decreases. The activation energy E, the entropy change S ^*, the enthalpy H ^* change and Gibbs free energy change G ^* were calculated from TG curve.This revised version was published online in November 2005 with corrections to the Cover Date.     

Metal complexes of fenoterol drug

Metal complexes of fenoterol (FEN) drug are prepared and characterized based on elemental analyses, IR, ¹H NMR, magnetic moment, molar conductance, and thermal analyses (TG and DTA) techniques. From the elemental analyses data, the complexes are formed in 1:2 [Metal]:[FEN] ratio and they are proposed to have the general formula [Cu(FEN)₂]·2H₂O; [M(FEN)₂(H₂O)₂]·yH₂O (where M = Mn(II) (y = 2), Co(II) (y = 4), Ni(II) (y = 4), and Zn(II) (y = 0) and [Cr(FEN)₂(H₂O)₂]Cl·H₂O. The molar conductance data reveal that all the metal chelates are non-electrolytes except Cr(III) complex, having 1:1 electrolyte. IR spectra show that FEN is coordinated to the metal ions in a uninegative bidentate manner with ON donor sites of the aliphatic –OH and secondary amine –NH. From the magnetic moment measurements, it is found that the geometrical structures of these complexes are octahedral (Cr(III), Mn(II), Co(II), Ni(II), and Zn(II)) and square planar (Cu(II)). The thermal behavior of these chelates is studied using thermogravimetric and differential thermal analyses (TG and DTA) techniques. The results obtained show that the hydrated complexes lose water molecules of hydration followed immediately by decomposition of the coordinated water and ligand molecules in the successive unseparate steps. The FEN drug, in comparison to its metal complexes is also screened for their antibacterial activity against bacterial species (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Salmonella typhi), Yeasts (Candida albicans and Saccharomyces cervisiae), and Fungi (Aspergillus niger and Aspergillus flavus). The activity data show that the metal complexes have antibacterial activity like that of the parent FEN drug against one or more species.     

Cleavage of iron2-alkenyl and iron2-alkynyl bonds by mercury(II) chloride

Reactions of HgCl₂ with η⁵-C₅H₅Fe(CO)₂R (R  CH₂CHCH₂ and CH₂C(CH₃)CH₂) in THF at 25°C rapidly afford $\text{1}\text{1}$ adducts of the two reactants. These adducts were converted to the corresponding PF₆^? salts, [η⁵-C₅H₅Fe(CO)₂(η²-CH₂C(R)CH₂HgCl)]⁺ PF₆^? (R  H and CH₃), for characterization. Slower reactions with cleavage of the ironcarbon σ bond and elimination of the R group from η⁵-C₅H₅Fe(CO)₂R occur for R  CH₂CHC(CH₃)₂, CH₂CHCHC₆H₅, and CH₂CCC₆H₅. Both elimination and $\text{1}\text{1}$ adduct formation are observed when R  CH₂CHCHCH₃. The kinetics of the cleavage reactions are presented and possible mechanisms for both cleavage and $\text{1}\text{1}$ adduct formation are discussed.     

Synthesis and Thermal Analysis of 2,2′-bipyridine Divalent Transition Metal Hexachloroplumbates

Several complex salts of the general formula [M(II) (bipy)_x(H₂O)_y]PbCl₆ (where x=2–3, y=0–2 and M=Mn(II), Fe(II), Ni(II), Co(II), Cu(II), Zn(II), Cd(II) and Hg(II)) were synthesized and investigated by DTA, TG and DTG. Some of the decomposition products were identified by IR spectroscopy and other methods. The compounds decompose with the liberation of water (in the case of hydrates), chlorine (sometimes causing chlorination of organic fragments), organic molecules (sometimes chlorinated) and sometimes hydrogen chloride. The residues comprise metal(II) chlorides and PbCl₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

Preparation of η2-acetylene- and η1-vinylidene-manganese complexes from p-diethynylbenzene and cymantrene. X-ray crystal and molecular structure of Cp(OC)2MnCCHC6H4CBrCH2

Cp(OC)₂Mn(THF) reacts with p-diethynylbenzene (Deb), yielding Cp(OC)₂Mn(Deb) (I) and [Cp(OC)₂Mn]₂(Deb) (II) with the η²-acetylene coordination of Deb (to both Mn atoms in II). Under the action of PhLi, I and II are isomerized into Cp(OC)₂MnCCHC₆H₄CCH (III) and [Cp(OC)₂MnCCH]₂C₆H₄ (VI). Treatment of I with PhLi, LiBr and an excess of HCl in ether, as well as direct interaction of III with LiBr and HCl/Et₂O, gives Cp(OC)₂MnCCHC₆H₄CBrCH₂ (IV), which has been characterized by an X-ray single-crystal diffraction study. III adds PPh₃, yielding a zwitterionic complex, Cp(OC)₂Mn⁻C(P⁺Ph₃)CHC₆H₄CCH (V).     

Thermal decomposition reactions of metal carboxylato complexes in the solid state. I.: Thermographic and differential thermal studies of metal oxalato,malonato and succinato complexes

Thermal investigation of metal carboxylato complexes of the first transition metals, Mn(II), Fe(II), Fe(III), Co(II), Ni(II) and Cu(II) and non-transition metals like Zn(II) and Cd(II) in the solid state has been carried out under non-isothermal conditions in nitrogen atmosphere by simultaneous TG and DTA. TG and DTA curves inferred that the thermal stability of the complex decreased approximately with the increase of the standard potential of the central metal ion. The thermal parameters like activation energy, E_a, enthalpy change, ΔH, and entropy change, ΔS, corresponding to the dehydration and decomposition of the complexes are determined from TG and DTA curves by standard methods. A linear correlation is found between ΔH and ΔS and E_a and ΔS in dehydration and decomposition processes. DTA curves show an irreversible phase transition for Na₂Mn(mal)₂], Na₂[Cu(mal)₂] and Na₂,[Co(suc)₂] complexes. The residual products in these decomposition processes being a mixture of two oxides, of oxide and carbonate or a mixture of two carbonates.     

Thermal Behaviour of the N-donor Adducts of Metal Saccharinates. II. 1,10-phenanthroline saccharinato complexes of Co(II), Ni(II), Cu(II), Zn(II) and Pb(II)

Adducts of Co(II), Ni(II), Cu(II), Zn(II) and Pb(II) saccharinates with 1,10-phenathroline were synthesized and their thermoanalytical (TG, DTG and DTA) curves in the 20–1000°C temperature interval and static air atmosphere were recorded. The complexes are best represented as M(C₁₂H₈N₂)_x(C₇H₄NO₃S)₂⋅yH₂O (x=2, 2, 2, 2 and 1; y=1, 1, 2, 1 and 2 for M=Co, Ni, Cu, Zn and Pb, respectively). The decomposition of the compounds regularly started with dehydration, followed by loss of the phenanthroline ligand(s). The structures of the Cu and Pb complexes are notably different from other compounds. FTIR spectra of the title compounds in the region of the OH, CO and SO₂ stretching vibrations were also studied. The pronounced similarity of the spectra of Co, Ni and Zn adducts indicates possible isomorphism among them. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dicyclopentadienyl-niobium(iii) and -niobium(iv) complexes

The reduction of (η-C₅H₅)₂NbCl₂ (I) under various conditions gives the dimer (η-C₅H₅)₄Nb₂Cl₃ (II) containing niobium(III) and niobium(IV). Reaction of II with AgClO₄ gives [(η-C₅H₅)₄Nb₂Cl₂]⁺ ClO₄^- (III). FeCl₃ and (C₆F₅)₂ TlBr displace I from II to give (η-C₅H₅)₂Nb(μ-Cl)(μ-X)MY₂, where MFe, XYCl(IV) and MTl, XBr, YC₆F₅ (V). Reactions of I with metal halides MXY₂ give (η-C₅H₅)₂ClNb(μ-Cl)MXY₂ where XYCl, MAl (VI), Fe (VII), Tl (VIII) and XBr, YC₆F₅, MTl (IX). The chemical behaviour of all these compounds is described.     

Reactions of 2,4,6-tripyridyl-1,3,5-s-triazine and its Fe(ii) complex with OH· and eaq-

Summary Pulse radiolysis studies indicated that OH^· and e_aq^- formed adducts with 2,4,6-tripyridyl-1,3,5-s-triazine (tptz). The OH-adduct showed an absorption maximum at 290 nm, while the adduct formed from the attack of e_aq^- and subsequent protonation of the anion, has an absorption maximum at 300 nm. In case of the complex, Fe(tptz)₂²⁺, both OH^· and e_aq^- gave ligand centered adducts. All the adducts decayed by second order dimerization or disproportionation, a disproportionation reaction in case of the complex.     

Ion cyclotron resonance studies of ambident nucleophiles. The reactions of the trimethylsilyl cation with alkenyl ethers and alkoxy ketones

Alkenyl ethers react through oxygen with Me₃Si⁺ to yield intermediates which undergo characteristic fragmentations. In the particular case of allyl ethers, the decomposing adduct undergoes several fragmentations through the allyl substituent via 6-membered transition states. The reaction between Me₃Si⁺ and alkoxy carbonyl derivatives yields both ‘ether’ and ‘keto’ adducts, characterized by their fragmentation patterns. The ‘ether’ adducts formed from Me₃Si⁺ and alkoxy acetones undergo the same basic eliminations as those observed for the allyl ether/Me₃Si⁺ systems.     

Complexation of rhodium(II) tetracarboxylates with aliphatic diamines in solution: 1H and 13C NMR and DFT investigations

The complexation of rhodium(II) tetraacetate, tetrakistrifluoroaceate and tetrakisoctanoate with a set of diamines (ethane‐1,diamine, propane‐1,3‐diamine and nonane‐1,9‐diamine) and their N,N′‐dimethyl and N,N,N′,N′‐tetramethyl derivatives in chloroform solution has been investigated by ¹H and ¹³C NMR spectroscopy and density functional theory (DFT) modelling. A combination of two bifunctional reagents, diamines and rhodium(II) tetracarboxylates, yielded insoluble coordination polymers as main products of complexation and various adducts in the solution, being in equilibrium with insoluble material. All diamines initially formed the 2 : 1 (blue), (1 : 1)_n oligomeric (red) and 1 : 2 (red) axial adducts in solution, depending on the reagents' molar ratio. Adducts of primary and secondary diamines decomposed in the presence of ligand excess, the former via unstable equatorial complexes. The complexation of secondary diamines slowed down the inversion at nitrogen atoms in NH(CH₃) functional groups and resulted in the formation of nitrogenous stereogenic centres, detectable by NMR. Axial adducts of tertiary diamines appeared to be relatively stable. The presence of long aliphatic chains in molecules (adducts of nonane‐1,9‐diamines or rhodium(II) tetrakisoctanoate) increased adduct solubility. Hypothetical structures of the equatorial adduct of rhodium(II) tetraacetate with ethane‐1,2‐diamine and their NMR parameters were explored by means of DFT calculations. Copyright © 2013 John Wiley & Sons, Ltd.     

Thermal decomposition reactions of metal carboxylato complexes in the solid state: II. Thermographic and differential thermal studies of metal oxalato,malonato and succinato complexes

The thermal investigations of metal carboxylato complexes of the first transition metals, Mn(II), Fe(II), Fe(III), Co(II), Ni(II) and Cu(II) and non transition metals like Zn(II) and Cd(II) in solid state were carried out under non-isothermal condition in nitrogen atmopshere by thermogravimetric (TG) and differential thermal analyses (DTA) methods. The results of DTA curves inferred that the thermal stability of the complex decreased approximately with the increase of standard potential of the central metal ion. The thermal parameters like activation energy (E_a¹), enthalpy change (ΔH) and entropy change (ΔS) corresponding to deaquation, deammoniation and decomposition processes occurred simultaneously or separately were determined from TG and DTA curves by the standard methods. A linear correlation has been found in the plots of ΔH vs. ΔS and E_a¹ vs. ΔS in deaquation, deammoniation and decomposition processes. An irreversible phase transition was noticed for H₂[Mn(suc)₂] and H₂[Co(suc)₂] complexes in DTA curves. The residual pyrolysed products were metal carbonates.     

Nickel(II) and cerium(IV) ethyleneurea,ethylenethiourea and propyleneurea adducts

The NiCl₂ · 6eu, NiCl₂ · 6etu, Ce(SO₄)₂ · 6pu and Ce(SO₄)₂ · 6etu adducts (eu = ethyleneurea, etu = ethylenethiourea and pu = propyleneurea) were prepared by a solid state procedure, and characterized by C, H and N elemental analysis, i.r. spectroscopy, thermogravimetry (t.g.) and differential scanning calorimetry (d.s.c.). The i.r. results show that eu and pu coordinate through oxygen, whereas etu coordinates through nitrogen. The NiCl₂ · 6eu adduct is green, whereas the NiCl₂ · 6etu adduct is yellow. This fact suggests that the _o separation is larger for the latter adduct. On the other hand, both cerium adducts are white, suggesting that, for pu and etu cerium sulfate adducts, a ligand-to-metal charge-transfer promotes the reduction of Ce^IV to Ce^III. The t.g. thermal stability sequences are: etu > pu > eu and Ni > Ce. Cerium adducts release the six ligand molecules in a single mass loss step, suggesting that all ligand molecules are in equivalent coordinative positions (same bond length and strength). On the other hand, nickel adducts exhibit three mass loss steps in the thermal degradation (release of ligand molecules) process. This suggests that, for these compounds, there are three distinct coordinative positions, with distinct bond lengths and strengths, probably due to the Jahn–Teller effect. All four adducts melt before the onset of thermal degradation, with etu adducts exhibiting the higher melting temperatures and melting enthalpies, as a consequence of stronger intermolecular forces.