Transition Metal Nitrogen Research Articles

Effect of Interaction between Transition Metal Oxides and Nitrogen Atoms on Thermal Stability of Polybenzoxazine

To investigate the interaction of transition metal oxides with polybenzoxazine and their influence on the thermal degradation mechanism of polybenzoxazine, transition metal oxides Y2O3, La2O3, Pr6O11, and Gd2O3 were added to benzoxazine monomer based on p-cresol and aniline to prepare polybenzoxazine composites. The chemical structures and final polymerization extent of polybenzoxazine and its composites were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and differential scanning colorimetry (DSC). The molecular weights of these cured samples were determined by gel permeation chromatography (GPC). The influence of transition metal oxides on the thermal properties of polybenzoxazine matrix was investigated using dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), thermogravimetric analyzer interfaced with Fourier transform infrared spectroscopy (TG-IR), and (pyrolysis-gas chromatography-mass spectrometry) Py-GC-MS. The results show that transition metal oxides can form coordination interactions with the nitrogen atoms of polybenzoxazine. The coordination interaction can anchor the aniline and make the molecular weights of polybenzoxazine matrix increase, which delays evaporation of aniline during thermal degradation, improves the char yield at 800°C, and increases the glass transition temperatures (Tg) of polybenzoxazine composites.

MNE Nitrido Bridges with Transition Metal Nitrogen Multiple Bonds and E = Phosphorus, Sulfur, and Chlorine

AbstractA compilation is given on new syntheses, properties, and structures of complexes with M≡N—E ↔ M=N=E nitrido bridges with transition metal nitrogen multiple bonds and participation of the main group elements E of phosporus, sulfur, and chlorine.1. MNP: This atomic sequence is realized in phosphoraneiminato complexes with transition metals in high oxidation states and termal bond of the (NPR3—) ligand. A series of new complexes of this type is reported with M = zirconium, hafnium, molybdenum, tungsten, and rhenium, among these the homoleptic species [Hf(NPPh3)4] and [M(NPPh3)4]2+ with M = Mo and W. Therefrom the isolobal complexes [:N≡Mo(NPPh3)3], [:O≡W(NPPh3)3]+, [(O)2Mo(NPPh3)2], and [(O)3Re(NPPh3)] are derived.2. MNS: Adding to compounds with this atomic sequence, new complexes were developed on the basis of the functional ligand groups thionitrosyl (a), dinitridosulphate(II) (b), dinitridosulphate(IV) (c), and cyclothiazeno (d) (cyclo‐3, 5‐dithia‐2, 4, 6‐triazino):magnified image3. MNCl: Novel N‐chloroimido complexes of tungsten are described. [F4W≡N—Cl]4, which is tetrameric according to the IR spectrum, was obtained by direct fluorination from [Cl4W≡N—Cl]2 or, surprisingly, from W(N)Cl3. With acetonitrile the monomeric molecular complex [CH3CN→WF4(≡N—Cl)] is formed. In an unexpected pathway K[F5W≡N—Cl] was obtained from a redox reaction of W(N)Cl3 with trimethylstannyl fluoride in the presence of potassium fluoride. The ionic compound forms double layers with short Cl···F contacts.

Phosphorane−Iminato Complexes of Transition Metals with Heterocubane Structure: A Computational Study

The electronic structure of phosphorane-iminato complexes of transition metals is studied by means of ab initio/DFT methods. Accordingly, the transition metal nitrogen bond is best described as an ionic interaction between a transition metal complex fragment and the strongly polarized NPH3- ligand. By elaborate MCSCF calculations a weak antiferromagnetic coupling of the four transition metal centers in the cubane core is predicted. This coupling can be represented by a simple Heisenberg Hamiltonian.

Electronic Structure of Metallacyclophosphazene and Metallacyclothiazene Complexes.

The electronic structure of metallacyclotriphosphazene complexes with several substituents at the phosphorus atoms and metallacyclothiazene complexes is explored for a variety of transition metal elements using density functional theory methods. Accordingly the metallacyclophosphazenes possess a large HOMO-LUMO energy separation while the metallacyclothiazenes bear stronger open-shell character. In addition our calculations predict the existence of experimentally so far unknown dimetallacyclophosphazenes. All structures show to be highly dynamical. The double bond character of the transition metal nitrogen bond is much less pronounced than in nitrido or imido complexes. For the ring compounds vibrational spectra are reported and compared with experimental data.

Electrochemistry of liquids vs. solids: Polymer electrolytes

The electrochemistry of polymers is reviewed, in comparison with solid or liquid electrolytes. It is shown that the coordination chemistry leading to the formation of conductive complexes is very general with specific interactions (e.g. transition metal-nitrogen). While the transference numbers are still the subject of controversies, a coordination chemistry akin to that of water for PEO or ammonia with PEI exists. Also, the possibility of redox conduction, through microphase separation leads to mixed conductivity (ions + electrons).

Electrochemical behaviour and polymerization of rhodium (III) complexes with tertiary phosphines and nitrogen ligands

A rapidly developing field concerned with the creation of new catalytic electrodes involves modification by polymer coatings [l]. An elegant method of electrode modification is the electropolymerization of a suitable monomer, since deposition of insoluble, stable and adherent films of controlled thickness is then possible. Among the numerous chemical functions that could undergo electrochemical polymerization, the pyrrole group is exceptionally convenient for carrying out the coating of electrode surfaces by stable and nonpassifying films containing catalytic centres [2]. In this way, films with a great variety of transition metalnitrogen ligand complexes have been deposited on electrode surfaces for applications in catalysis [2]. Although metal-phosphine complexes display wide-ranging catalytic activity, we are not aware of any report of successful electrode modification by electropolymerization involving such complexes. This may be due to the fact that pyrrole-functionalized metal-phosphine complexes would be difficult to synthesize. In addition, the metal complex must be stable at the positive potential required to polymerize the pyrrole group. In the pursuit of our interest in the preparation of transition metal-based catalytic electrode materials [371, we now report our preliminary electrochemical investigations of [RMCl),(P),(L)]+ and [Rh(HI,(P),(L)]+ complexes (P = PPh, or PPh,Et; L = 2,2’-bipyridine derivative). This paper describes the first example of

On the stable compositions in transition metal-nitrogen phase diagrams

It is explained why there can be no stable nitrogen-rich compounds in transition metal-nitrogen (M-N) binary systems. In addition it is demonstrated how the stability of a given nitride can be described as a function of temperature and pressure. Predictions of the enthalpy are tabulated for all M-N combinations at three compositions (M. 0.67N 0.33, M 0.5N 0.5, M 0.4N 0.6) and are compared with experimental results.

Reactions of transition metal-nitrogen .sigma. bonds. 3. Early transition metal N,N-dimethylcarbamates. Preparation, properties, and carbon dioxide exchange reactions

Reactions of transition metal-nitrogen .sigma. bonds. 3. Early transition metal N,N-dimethylcarbamates. Preparation, properties, and carbon dioxide exchange reactions

Reactions of transition metal-nitrogen .sigma. bonds. 4. Mechanistic studies of carbon dioxide insertion and carbon dioxide exchange reactions involving early transition metal dimethylamido and N,N-dimethylcarbamato compounds

Reactions of transition metal-nitrogen .sigma. bonds. 4. Mechanistic studies of carbon dioxide insertion and carbon dioxide exchange reactions involving early transition metal dimethylamido and N,N-dimethylcarbamato compounds

Organonitrogen groups in metal carbonyl complexes. Part X. Carbonylation studies

A possible mechanism for the carbonylation of amines and other nitrogen-containing molecules, which involves insertion into a transition metal–nitrogen bond, has been tested. Attempts to insert carbon monoxide into such bonds of [M(η5-C5H5)(CO)2X][M = Mo or W; X = N:CR2(R = But or p-tolyl), R2CNCR2(R = Ph, p-tolyl, or p-CF3C6H4), RNC(R′)NR (R = R′= Ph; R = Ph, R′=p-tolyl)], [Mn(CO)4X]{X = RNC(R′)NR (R = R′= Ph)}, and [Fe(π-C5H5)(CO)2(Nph2)], produced [{(η5-C5H5)M(CO)n}2](M = Mo or W, n= 3: M = Fe, n= 2) and/or the binary metal carbonyls. No evidence was obtained for the formation of carbamoyl complexes.

Reactions of transition metal-nitrogen .sigma.-bonds. II. Pentakis(N,N-dimethylcarbamato)niobium(V) and its facile exchange reaction with carbon dioxide

Reactions of transition metal-nitrogen .sigma.-bonds. II. Pentakis(N,N-dimethylcarbamato)niobium(V) and its facile exchange reaction with carbon dioxide

The reactions of organometallic compounds of transition metals with molecular nitrogen and carbon dioxide

A development of organometallic chemistry has revealed wide possibilities for activating various unsaturated and saturated molecules for numerous novel reactions. Many nitrogen fixating systems based on the low-valent transition metal derivatives and reducing agents have been discovered. Depending on the reaction conditions, complexed nitrogen reduction occurs to form either hydrazine derivatives or ammonia. An investigation of the nitrogen fixating systems involving Lewis acids, to regenerate the catalyst, has led to catalytic nitrogen fixation. Nitrogen activated by complex formation with transition metal compounds is capable of insertion reactions into metal—carbon bonds to form organic amines. In this connection the possibility arises of forming amines from the reaction of nitrogen with hydrocarbons in the presence of transition metal compounds. Transition metal nitrogen compounds seem to be intermediates in the 'reverse' reactions as well, i.e. decompositions of nitrogencompounds with nitrogen evolution (Sandmeyer reaction, hydrazine oxidation. etc). Unlike nitrogen, carbon dioxide is rather reactive and undergoes insertion reactions into non-transition metal-carbon boids. Carbon dioxide also appeared to be capable of direct or indirect complex formation with low-valent transition metal compounds (Ru, Rh, Pt, etc.). Investigation of the stability of such complexes permits novel synthetic and catalytic reactions to be found. Thus the formation of Me—H bonds (e.g. in the formic acid decomposition with CO2 evolution) can be utilized for catalytic reduction of olefins and other unsaturated compounds by means of formic acid. When the intermediate carbon dioxide complexes with Me—C bonds (carboxylates) are formed. the competitive reaction occurs, i.e. olefin insertion into Me—H or Me—C bonds with elimination of the respective carboxylic acid. Another interesting reaction, insertion of CO2 into Me—H or Me—C bonds, can follow either 'normal' (formation of a carbon-carbon' bond) or 'reverse' (formation of the metalloacid ester) pathways. A development of organometallic chemistry has provided unusual possibilities for activating various unsaturated and saturated molecules and introducing them into the various reactions. The present lecture deals with the problem of activation by transition 607

Binary transition metal nitrogen compounds; infrared evidence for Ni(N2) x

I. r. evidence suggests that nickel atoms react with nitrogen molecules in low temperature matrices to produce the dinitrogenyls of general formula Ni(N2)x where x is probably 1 or 2.