Refractory Metal-Containing Polymers and Nanocomposites: Preparation and Properties

Summary: Novel polymers containing refractory metal in the main chain or side chains can be prepared. An attractive approach is polymerization of the Hf (Ta, Nb)-monomers with (meth)acrylate, fumarate or monomethylmethacrylate ethyleneglycol groups, synthesized for the first time in this study. New types of hafnium (tantalum, niobium)-containing nanocomposites are prepared by combining polymer synthesis and controlled thermolysis. The composition and structure of the synthesized metal-containing precursors and thermolysis products are determined by elemental analysis, IR and ¹H-NMR spectroscopies, X-ray diffraction and TEM analysis.     

Preparation and reactivity of metal-containing monomers. 12. Metallochelate monomers based on N-(2-pyridyl)methylacrylamide

Metallochelate monomers have been synthesized on the basis of N-(2-pyridyl)methylacrylamide. On the basis of data obtained by IR and UV spectroscopy and magnetochemistry, it is concluded that the metal ion has an octahedral configuration in the compounds obtained. The diffuse reflection spectra indicate that the metal-ligand bond in the chromium(III) complex is covalent in character, with a 0.375 degree of covalency.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2474–2477, November, 1989.     

Photochemistry of cyclohexene oxide radical cations in freonic matrices at 77 K

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Synthesis, structure, and catalytic properties of polymer-immobilized rhodium clusters

Immobilized Rh₆ clusters (cyclohexene hydrogenation catalysts) were prepared by the polymer-analogous transformations or copolymerization of cluster-containing monomers and characterized. Intermediates formed in the course of a catalytic reaction were studied using IR spectroscopy, XPS, and atomic force microscopy. It was found that the relative intensity of a low-energy line in the Rh3d _5/2 spectrum of the initial polymer-immobilized cluster in the XPS spectrum of Rh₆ increased in the course of hydrogenation. The catalytic activity of the immobilized complex changed symbatically with both the number of Rh atoms bound to the H(CO) group and the number of Rh atoms, the charge on which was greater than that in the parent cluster. Some experimental evidence was obtained in favor of the hypothesis of cluster fragmentation in the course of hydrogenation with the formation of highly active, most likely, nanosized particles, which are true catalysts, in low concentrations. The surface of macrocomplex particles after hydrogenation became more homogeneous and hydrophilic; this fact is also indicative of an increase in the concentration of polar functional groups in surface layers. This was likely due to Rh-Rh bond cleavage in the polymer-immobilized cluster.     

Preparation and reactivity of metal-containing monomers

Starting with the trinuclear clusters, M₃(CO)₁₂ (where M=Os or Ru), Os₃(CO)₁₁(NCCH₃), Os₃(CO)₁₀(NCCH₃)₂, and (-H)Os₃(-OR)(CO)₁₀ (where R=H or Ph), and polyfunctional organic compounds containing vinyl or allyl groups, a number of cluster monomeric complexes have been synthesized containing ligands with an uncoordinated C=C bond,viz.: (-H)Os₃(-4-Vpy)(CO)₁₀, (-H)Os₃(-O₂CCH=CH₂)(CO)₁₀, (-H)Os₃(-OCNHCH₂CH=CH₂)(CO)₁₀, and (-H)M₃(-SCH₂CH=CH₂)(CO)₁₀. The (-H)Os₃(-4-Vpy)(PPh₃)(CO)₉ complex was investigated by X-ray diffraction analysis.For part 30, seeRuss. Chem. Bull., 1993,42, 1016.Vpy is the vinylpyridine ligand.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1293–1298, July, 1993.     

Synthesis and reactivity of metal-containing monomers 49. Synthesis and structure of low-valence transition metal acrylates and their polymers

The methods for synthesis of Cu¹⁺, Fe²⁺, Cr²⁺, and V³⁺ acrylates were elaborated. The compounds obtained were characterized by elemental analyses, data of IR, X-ray photoelectron, and Mössbauer spectroscopy, magnetochemistry, and mass spectrometry. Polymeric products were obtained by liquid-phase radical polymerization of metal acrylates. Changes in the electronic state of the ions and their nearest ligand environment during polymerization were observed.     

Preparation and reactivity of metal-containing monomers. 17. Spatial and electronic structure of complexes of cobalt nitrate and chloride with acrylamide

We have investigated the spatial and electronic structure of the complexes [Co(AAm)₄(H₂O)₂](NO₃)₂ and Co(AAm)₄Cl₂ by electronic spectroscopy. The complex of cobalt nitrate with acrylamide (AAm) has a pseudooctahedral structure in the crystalline state and in organic solvents, and the metal-ligand bonds are covalent to a significant degree. For the complex of cobalt chloride with AAm, a change in the spatial structure is characteristic upon going from the crystal (tegragonally distorted octahedron) to the solution (tetrahedron). For a Co(AAm)₄Cl₂ single crystal, we determined the sequence of the energy levels with the ground-state⁴A_2g-term. The high values of the McClure parameters, taking into account the contributions of the ligands to the and bonds, are evidence for coordination of the acrylamide through the oxygen atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1319–1323, June, 1990.