Reactive properties of phosphine complexes of some transition metals in ethylene carbonylation

Catalystic properties of Group VIII transition metals and Cu, Ag, Au and Hg compounds in diethylketon synthesis from ethylene, carbon monoxide and hydrogen in concentrated aqueous solutions of trifluoroacetic acid containing triphenylphosphine have been examined in mild conditions (70°C, 1 bar). It has been established that under these conditions, in addition to Pd axcetate, a noticeable activity in diethylketone synthesis is observed only for Pt and Rh compounds.

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VIII , Cu, Ag, Au Hg , , , (70°C, 1 ). , Pd Pt Rh .

     

Porphyrin complexes of the period 6 main group and late transition metals

Metalloporphyrin complexes of the period six metals gold, mercury, thallium, lead and bismuth are often overlooked in favour of their lighter congeners. These complexes exhibit unusual coordination geometries, prominently featuring the metal centre residing out the porphyrin plane. Not only are these compounds chemically interesting, but several applications for these complexes are beginning to emerge. Gold and bismuth porphyrins have medicinal applications including novel chemotherapeutics and sensitizers for α-radiotherapy, while gold porphyrins have applications in materials chemistry and catalysis. This perspective serves to highlight trends in the synthesis and structure of these heavy metal complexes as well as illustrate the considerations necessary for rationally designing elaborate porphyrin architectures.     

Norbornadiene complexes of transition metals

Conclusions Correlations were established between the stereochemistry of 2-(-carbinol)norbornadiene complexes of rhodium and their mass spectra.This study is also communication 30 from the series Mass Spectrometry of Transition Metal- Complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2701–2703, December, 1982.     

New bimetallic complexes of late transition metals involving pyrazole-bridged bis N-heterocyclic carbene ligands

Bimetallic Ni, Rh, and Ir complexes of pyrazolate biscarbene containing bulky substituents have been synthesized and characterized by X-ray crystallography; the Ni complex dimerizes to a highly congested L(2)Ni(2) structure, whereas the corresponding Rh and Ir complexes form bimetallic LM(2) structures.     

Thermal investigations of cefadroxil complexes with transition metals

The cefadroxil (Cef) complexes with transition divalent metals of the formula MCef·nH₂O (where n=2 for M=Cu²⁺, Ni²⁺, Zn²⁺ and n=3 for Co²⁺) and CdCef_1.5·4H₂O were prepared and characterized by elemental and infrared spectra. The thermal analysis of the investigated complexes in air atmosphere was carried out by means of simultaneous TG-DSC technique. During heating in air they lose bound water molecules and then decompose to oxides: Co₃O₄, NiO, CuO, ZnO and CdO. The CdCef_1.5·4H₂O complex forms probably an intermediate product Cd₂OSO₄. The combined TG-FTIR technique was employed to study of decomposition pathway of the investigated complexes. The first mass loss step is the water loss of the complexes. Next, decomposition of cefadroxil ligand occurs with evolution of CO₂ and NH₃. At slightly higher temperature COS is observed according to decomposition of cephem ring. Additionally, as decomposition gaseous products: HCN, HNCO (HOCN), H₂CNH, CO, SO₂, hydrocarbons and carbonyl compounds were observed. The formation of metal sulfates is postulated as solid intermediate product of decomposition in the argon atmosphere. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and characterization of new complexes of some divalent transition metals with 2-acetyl-pyridyl-isonicotinoylhydrazone

Ten new mononuclear complexes having general formulae [ML₂](ClO₄)₂, M = Cu(II), Co(II), Ni(II), Mn(II) and Zn(II), [ML₂](SO₄), M = Co(II), Ni(II) and [ML₂(H₂O)₂](SO₄), M = Cu(II), Mn(II) and Zn(II), L = 2-acetyl-pyridyl-isonicotinoylhydrazone have been synthesized and characterized based on elemental analyses, IR spectroscopy, UV–Vis–NIR, EPR, as well as thermal analysis and determination of molar conductivity and magnetic moments. The structures of [CoL₂](ClO₄)₂ are accomplished by single crystal X-ray diffraction. The coordination sphere is formed by two N, N, O tridentates 2-acetyl-pyridyl-isonicotinoylhydrazone ligands, or by two N, O bidentate 2-acetyl-pyridyl-isonicotinoylhydrazone and two water molecules. Biological activity studies reveal a moderate activity of complexes against gram-negative and gram-positive bacteria.     

Polymerization of hex-1-ene initiated by diimine complexes of nickel and palladium

The effect of monomer concentration, reaction temperature and initiator structure on the activity, molar mass, branching and thermal properties of poly(hex-1-ene)s was investigated for the polymerization of hex-1-ene initiated by four α-diimine complexes of nickel and palladium. Hex-1-ene polymerization exhibits an apparent negative kinetic order with respect to monomer concentration. Polymerization of hex-1-ene initiated by MAO activated 1,4-bis(2,6-diisopropylphenyl)acenaphtenediiminenickel(II) dibromide (1a/MAO) proceeds in living-like fashion not only at sub-zero temperatures but even at 20 °C. However, molar masses of the polymers are higher than predicted values in agreement with an initiator efficiency lower than one.     

Polymerization catalysis with transition metal amidinate and related complexes

Applications of transition metal amidinate [RC(NR′)₂], guanidinate and amidopyridine complexes to olefin coordination polymerization are reviewed. In addition, the use of complexes, featuring closely related ligands, such as phosphonamide or iminophosphonamide [R₂P(NR′)₂], in olefin polymerization is highlighted. Some of these complexes have also been investigated in the stereoregular polymerization of styrene and conjugated dienes, whereas more recent work has focused on controlled ring-opening polymerization of lactones and lactides.     

Polymer derived non-oxide ceramics modified with late transition metals

This tutorial review highlights the methods for the preparation of metal modified precursor derived ceramics (PDCs) and concentrates on the rare non-oxide systems enhanced with late transition metals. In addition to the main synthetic strategies for modified SiC and SiCN ceramics, an overview of the morphologies, structures and compositions of both, ceramic materials and metal (nano) particles, is presented. Potential magnetic and catalytic applications have been discussed for the so manufactured metal containing non-oxide ceramics.     

Vibrational spectra of complexes of norbornadiene with transition metals

Russian Chemical Bulletin -     

Thermodecomposition ofo-benzoquinone complexes of transition metals

Thermodecomposition of 3,5- and 3,6-di-tert-butyl-o-benzoquinone complexes of Cu, Fe, Co, Cr, Mo, and W has been investigated in the solid phase by the thermogravimetric method. The relative stability of a series of complexes has been determined from the temperatures at which their decomposition begins. Detachment of a neutral electron-donor ligand takes place in the first stage. Detachment of ano-quinone ligand and decomposition of theo-benzoquinone formed occur in the next stage. Thermodecomposition of Fe, Co, Cr, Mo, and W complexes gives oxides or carbides, while copper complexes decompose to pure metal.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 327–329, February, 1994.     

Dihydrogen complexes of the transition metals

Summary The binding and activation of dihydrogen by simple transition metal complexes is of fundamental importance in processes as diverse as the homogeneous or heterogeneous hydrogenation of unsaturated organic molecules⁽¹⁾ and understanding how metalloenzymes such as nitrogenase⁽²⁾ and the hydrogenases⁽³⁾ work at the atomic level.Simple consideration of the oxidative-addition of dihydrogen to a coordinatively-unsaturated complex {or its reverse (reductive-elimination)} reveals that the reactions are compelled to proceed via a dihydrogen complex as shown in Equation (1). However until recently it was considered that the dihydrogen complex had only a fleeting existence. Although there had been some reports in the literature such as that by Ashworth and Singleton⁽⁴⁾ that the formally Ru^IV trihydride, [RuH₃(PMe₂Ph₂]⁺ was better formulated as the Ru¹¹ species [RuH(H₂)(PMe₂Ph)₂]⁺, these could not be substantiated. In 1984, though, Kubas showed that the apparently innocuous complex [WH₂(CO)₃(PPr ₃ ⁱ )₂] contained the side-on bonded dihydrogen molecule, established unambiguously by x-ray, and neutron crystallography and spectroscopy⁽⁵⁾. In this highlight the current status of dihydrogen complexes, their structure, identification and in particular their reactivity will be discussed.     

Transmetalation reactions from Fischer carbene complexes to late transition metals: a DFT study

Transmetalation reactions from chromium(0) Fischer carbene complexes to late-transition-metal complexes (palladium(0), copper(I), and rhodium(I)) have been studied computationally by density functional theory. The computational data were compared with the available experimental data. In this study, the different reaction pathways involving the different metal atoms have been compared with each other in terms of their activation barriers and reaction energies. Although the reaction profiles for the transmetalation reactions to palladium and copper are quite similar, the computed energy values indicate that the process involving palladium as catalyst is more favorable than that involving copper. In contrast to these transformations, which occur via triangular heterobimetallic species, the transmetalation reaction to rhodium leads to a new heterobimetallic species in which a carbonyl ligand is also transferred from the Fischer carbene to the rhodium catalyst. Moreover, the structure and bonding situation of the so far elusive heterobimetallic complexes are briefly discussed.     

Trimellitate complexes of divalent transition metals with hydrazinium cation

New dihydrazinium divalent transition metal trimellitate hydrates of empirical formula (N₂H₅)₂M(Html)₂·nH₂O, where n = 1 for M = Co or Ni, and n = 2 for M = Mn, Zn, or Cd (H₃tml = trimellitic acid), and monohydrazinium cadmium trimellitate, [(N₂H₅)Cd(Html)_1.5·2H₂O] have been prepared and characterized by physico-chemical methods. Electronic spectroscopic, and magnetic moment data suggest that Co and Ni complexes adopt an octahedral geometry. The IR spectra confirm the presence of monodentate carboxylate anion (Δν = ν_asy(COO^?) ? ν_sym(COO^?) > 190 cm^?1) and coordinated N₂H₅ ⁺ ion (ν_N–N 1015 ? 990 cm^?1) in all the complexes. All the complexes undergo endothermic decomposition eliminating CO₂ in the temperature region 200–250 °C, followed by exothermic decomposition (in the range of 500–570 °C) of organic moiety to give the respective metal carbonate as the end products except nickel and cobalt complexes, which leave respective metal oxides. X-ray powder diffraction patterns reveal that Ni and Co complexes are isomorphous as are those of, Zn(II) and Cd(II) of the type, (N₂H₅)₂M(Html)₂·2H₂O.     

Macrocyclic complexes of transition metals with divalent polyaza units

A new series of 14–16-membered hexaazamacrocyclic complexes [ML¹X₂] and [ML²X₂] (M = Co^II, Ni^II, Cu^II and Zn^II; X = Cl or NO₃) have been synthesized by template condensation of phenylenediamine, primary diamines and formaldehyde solution 35% in MeOH and have been characterized by i.r., 1H-n.m.r., e.p.r., and u.v. spectroscopy as well as by magnetic susceptibility and conductivity measurements. An octahedral geometry has been suggested for all the complexes.     

Novel crown-containing porphyrin and its complexes with transition metals

The novel crown-containing porphyrin 5-{4-[(4-hydroxybenzo-15-crown-5)-5-yldiazo]phenyl}-10,15,20-triphenylporphyrin (H₃L) and its transition metal complexes MHL (M = Co(II), Ni(II), Cu(II), and Zn(II)) and AgH₂L were obtained. The compositions and structures of all the compounds were studied by MALDI-TOF mass spectroscopy, electronic absorption and IR spectroscopy. The diamagnetic compounds were additionally characterized by ¹H NMR spectroscopy. It was proved that Co(II), Ni(II), Cu(II), and Zn(II) are coordinated through the pyrrole N atoms, while Ag(I) is coordinated through the hydroxyl O atom and the diazo N atom of H₃L.