Zh. L. Dykh

Structure and catalytic activity of supported metal complexes. Communication 2. Synthesis of rhodium complexes on silica gel modified by phosphorus- and nitrogen-containing ligands

Conclusions1.Silica gel has been modified by aminophosphine groups and rhodium complexes immobilized on it: [RhCl(COD)]2, RhCl(PPh3)3, and RhCl3. IR spectroscopy was used to follow the formation of aminophosphine groups on the surface of the silica gel as the γ-aminopropyl silica reacted with the Ph2PCl.2.Using IR spectroscopy and GLC it has been shown that bonding of [RhCl(COD)]2 on a γ-aminopropyl-containing silica gel proceeds without replacement, while on the γ-aminophosphino-propyl-containing silica gel, the cyclooctadiene ligand is replaced. When complexes become bound to the latter support, the rhodium atom coordinates through the phosphorus atom of the aminophosphine group; the extent to which the nitrogen participates depends on the identity of the type of compounds immobilized.3.The activity and selectivity exhibited by the catalysts obtained in the conversion of the allylbenzene depends on the nature of the bonded ligand and the starting complex, the degree of ligand exchange, and the properties of the solvent.

Structure and catalytic activity of metallocomplexes immobilized on carriers

Mono-, bi-, and trinuclear Ru complexes with various ligands immobilized on the surface of silica gels modified with γ-aminopropyl, formamide, sulfide, cyano, or mercapto groups, catalyze hydrodehalogenation ofp-bromotoluene by the transfer of hydrogen from NaBH4 in 2-propanol both in an Ar atmosphere and in air. The structures of the heterogenized metallocomplex catalysts prepared (the nature of the ligand environment, the oxidation number of the central atom) were studied by IR and XP spectroscopy. The immobilized binuclear RuII,III tetraacetate, which retains the structure of the original complex, exhibits higher catalytic activity in the hydrogenolysis ofp-bromotoluene than heterogenized mononuclear systems.

Structure and catalytic activity of metal complexes fixed on carriers. Hydrodehalogenation of p-bromotoluene with chemically bonded hydrogen, catalyzed by immobilized rhodium(II) complexes

The structure of Rh(II) complexes with vigorous ligands immobilized on γ-aminopropyl-containing silicagel (γ-AMPS) and polymers containing 3(5)-methyl-pyrazole and imidazole groups, was investigated. It was shown by IR spectroscopy that the ligand surroundings are maintained after application only for the Rh(II) acetate complex. For the acetonitrile and hexafluoroacetylacetonate complexes there is a replacement of the ligands by amino groups of the carrier. [Rh2(O2CCH3)4] is significantly more active than other metal complexes immobilized on γ-AMPS in the hydrodehalogenation of p-bromotoluene by transfer of hydrogen from NaBH4 and propanol-2.

Structure and catalytic activity of metal complexes on carriers 3. Rhodium complexes on modified polymers and their catalytic properties in the reduction of nitrobenzene by chemically bound hydrogen

Heterogenized catalysts based on rhodium complexes attached to polymers modified by the groups 3(5)-methylpyrazole, imidazole and benzimidazole have been synthesized. The process of their formation has been investigated by IR, UV, and EPR spectroscopy. Results have been obtained for the catalytic activity of the complexes in the hydrogenation of nitrobenzene by hydrogen transfer from propan-2-ol and NaBH4.

IR spectra of catalysts and adsorbed molecules. 33. Formation of nickel-complex catalysts on various mineral supports

Conclusions1.The process of formation of nickel-complex catalysts from nickel carbonyl Ni(CO)4 and an allyl halide, C3H5X, on the surface of mineral oxide supports (Al203, Si02 and MgO) was investigated. The strong effect of the support on complexing was demonstrated a bis-π-allyl nickel halide is formed on Al203, together with other complexes on Si02, but not on MgO.2.The bis-π-allyl nickel complex is stabilized on the surface of the Al203 by reaction with coordination-unsaturated aluminum ions and surface OH groups. Ni(CO)4 and C3H5X react on the surface of SiO2 with formation of several types of complexes: monomeric and dimeric forms of π-allyl nickel halide and a complex of nickel and vinyl acetyl halide.3.Dehydrohalogenation of C3H3X with formation of allene and a hydrocarbon halide takes place on the surface of MgO in the reaction of Ni(OH)4 and C3H5X: The hydrocarbon halide reacts with the basic surface of the MgO with liberation of water; under the effect of the Ni(CO)4 and the MgO, the C3H5X yields diallyl, which forms a π-complex with nickel.

IR spectra of catalysts and adsorbed molecules. 39. Acid and catalytic properties of pentasils modified with platinum, chromium, and zinc

It was shown that when platinum is incorporated in pentasil (HZSM), the concentration of L sites increases by ∼2 times with no change in the number of B sites; in Pt-Cr-containing catalysts, the concentration of L sites passes through a maximum with a 0.72% concentration of Cr, and the number of OH groups and B sites decreases. The concentration of B sites decreases and the concentration of L sites increases in samples simultaneously promoted with Pt, Cr, and Zn. In conditions of aromatization of lower alkanes on Pt-Cr-containing catalysts, the concentration of OH groups and B sites decreases, while the concentration of L sites increases. Incorporation of platinum in HZSM increases the aromatizing activity with respect to methane, and additional incorporation of chromium and zinc increases the yield of aromatic hydrocarbons from ethane and propane also.

Properties of pentasil-containing catalysts in hydrocarbon conversions 6. Formation of condensation products during aromatization of propane on pentasils modified by zinc and gallium

Condensation products (CP) formation during the aromatization of propane on pentasils modified by Zn and Ga (1–5%) has been studied by IR spectroscopy, and thermal and chemical analyses. The amount of CP increases with increasing Zn concentration but falls with increasing Ga concentration in the catalyst. CP are formed both in the channels and on the exterior surfaces and are of an aromatic nature. Coking occurs to a greater extent and the CP are more dehydrogenated for Zn-containing samples than for those containing Ga. A relationship has been noted between the processes of formation of condensed aromatic hydrocarbons, CP, and methane.

Study of the catalytic properties of pentasil-containing composites in transformation of hydrocarbons 4. Formation of products of condensation during oligomerization and aromatization of ethylene on the pentasil-aluminum oxide system

The process of formation of products of condensation (PC) during oligomerization (280°C) and aromatization (500°C) of ethylene in the presence of H-pentasil (HTsVM)-γ-Al2O3 was studied by IR spectroscopy, DTA, DTG, and chemical analysis. The mutual effect of the components of the composite on the formation of PC in aromatization of C2H4 was detected. PC are formed with the participation of acid sites both inside the channels and on the outer surface of the zeolite. Three types of PC were found: linear polyene structures with C/H=0.8 (oligomerization), aromatic structures with C/H=1.5 (aromatization on HTsVM), and crosslinked polyene structures with C/H=2.45 (aromatization on Al2O3). The composition and structure of the PC formed on HTsVM during transformations of ethylene are a function of the molecular-sieve properties of the pentasil and the experimental conditions.

IR spectra of catalysts and adsorbed molecules. 38. Zinc-containing pentasils: Acid properties and transformations of ethane

Conclusions1.The Zn-pentasil system was studied by IR spectroscopy based on adsorption of pyridine. It was shown that zinc ions enter cation-exchange sites which are strong B sites. The Zn-HTsVM system is characterized in the general case by the presence of two types of B sites (strongly and weakly acid) and three types of L sites (lattice, Zn2+ in cation-exchange sites, and Zn2+ in the composition of the excess ZnO phase or cluster).2.The catalytic activity of HTsVM and Zn-HTsVM was studied in reactions of transformation of ethane. The aromatizing activity increases on addition of Zn2+ and attains the maximum with total exchange of protons in the cation-exchange sites for Zn2+. The Zn2+ ions not entering cation-exchange sites drive side reactions of methane formation and condensation.

Structure and catalytic activity of metal complexes immobilized on supports. Part 1. The synthesis of palladium complexes on silica gel, modified by aldiminopropylheteryl groups, and their properties

Conclusions1.Based on silica gel containing a γ-aminopropyl group and α-, Β-, and γ-aldehydes of the heterocyclic series supports having graft aldimine groups and their stable complexes with palladium have been obtained.2.It has been established by IR spectroscopy that the hydroxyl coating of silica gel is almost completely replaced by functional groups of ligands combined with the surface.