Paolo Pertici

An Ru-based catalytic membrane reactor for dry reforming of methane : its catalytic performance compared with tubular packed bed reactors

The methane reforming with CO2 seems to be a promising reaction system useful to reduce the greenhouse contribution of both gases into the atmosphere. On this basis, and considering the potentiality of this reaction system, the dry reforming reaction has been carried out in an Ru-based ceramic tubular membrane reactor, in which two Ru depositions have been performed using the co-condensation technique. Experimental results in terms of CH4 and CO2 conversion versus temperature during time are presented, as well as product selectivity and carbon deposition. These experiments have also been carried out using a traditional reactor. A comparison with literature data regarding dry reforming reaction is also provided. Experimental evidence points out a good catalyst activity for the methane dry reforming reaction, confirming the potentiality of a catalytic membrane applied to the reaction system.

(η6-Cyclohepta-1,3,5-triene)(η4-cycloocta-1,5-diene)iron(0) complex as attractive precursor in catalysis

The catalytic activity of the complex Fe(η6-CHT)(η4-COD), (CHT=1,3,5-cycloheptatriene; COD=1,5-cyclooctadiene), 1, has been evaluated in some reference reactions such as the hydroformylation of 1-hexene and styrene and the cyclotrimerisation of a wide range of terminal and internal acetylenes. The title complex has been found to be a convenient catalytic precursor and it resulted more active than other iron catalysts in the investigated reactions.

1-Hexene rhodium-catalyzed hydroformylation at partial substrate conversion: influence of reaction parameters on the chemoselectivtty and regioselectivity

Abstract The influence of the reaction parameters (temperature, gas pressure) on the chemo- and regioselectivity of 1-hexene hydroformylation in the presence of Rh4(CO)12 as catalytic precursor has been investigated at partial and complete conversion. Both chemo- and regioselectivity are independent of the substrate conversion until 1-hexene is present in the reaction mixture. Chemoselectivity to aldehydes is complete at room temperature, while at higher temperatures it decreases with decreasing pressure and increasing temperature as a consequence of 1-hexene isomerization to (E)- and (Z)-2-hexenes. Similar amounts of heptanal and 2-methylhexanal are obtained at room temperature. At higher temperature and partial substrate conversion, only 1-hexene is converted to aldehydes; the regioselectivity towards the linear isomer increases from 4% at room temperature to 48% at 120 °C and is not affected by the gas pressure. Differing behaviours of the linear and branched alkyl metal intermediates towards the β-hydride elimination under the reaction conditions account for the influence of the reaction parameters on the chemo- and regioselectivity in 1-alkene hydroformylation.

Hydrosilylation of aromatic nitriles promoted by solvated rhodium atom-derived catalysts

Abstract Rhodium metal particles, isolated as supported or unsupported powder starting from mesitylene solvated rhodium atoms, catalyse the hydrosilylation of aromatic nitriles to N , N -disilylamines in high conversion at 100°C. Different hydrosilanes (HSiMe 3 , HSi(OEt) 3 ) can be employed. In the case of cinnamonitrile, the chemoselectivity of the reaction to 2-trimethylsilyl-3-phenylpropionitrile and ( E )- and ( Z )-1-di(trimethylsilyl)amino-3-phenyl-1-propene is strongly dependent on the reaction temperature. The commercial rhodium on γ-Al 2 O 3 catalyst is considerably less active and selective than the analogous catalyst prepared via Metal Vapour Synthesis (MVS) probably owing to the different dimension and distribution of the metal particles in the two samples as shown by HRTEM analysis.

Supported ruthenium nanoparticles on polyorganophosphazenes: preparation, structural and catalytic studies

Abstract Supported Ru nanoparticles on a number of polyorganophosphazenes were prepared and tested for the hydrogenation of unsaturated compounds. The complex Ru(η6-cycloocta-1,3,5-triene)(η4-cycloocta-1,5-diene) was found to be a suitable precursor to deposit metallic nanoparticles on polyorganophosphazenes; upon the removal of cycloolefin ligands under hydrogen atmosphere, highly dispersed metal particles on the polymeric support can be obtained. Ru on polydimethylphosphazene was found to be an active catalyst for the hydrogenation of a wide range of unsaturated substrates (olefins, carbonyl compounds and aromatic compounds) under mild conditions. Polyorganophosphazenes are interesting in their ability to act as either soluble or insoluble catalyst supports, depending upon the dispersing liquid; thus, it is possible to operate in heterogeneous phase as well as in homogeneous phase. The reaction in homogeneous phase can be performed in environmental-friendly solvents such as alcohols and water. The catalyst exhibits high stability towards agglomeration. No significant change in the ruthenium nanoparticles surface as well as catalyst activity was observed.

Versatile polystyrene—ruthenium hydrogenation catalysts

Abstract Polymer—ruthenium complexes have been prepared by reacting (η 6 -cyclo-octa-1,3,5,-triene) (η 4 -cyclo-octa-1,5-diene)ruthenium(0),[(η 6 -cyclo-octa-1,3,5-triene) (COT); (η 4 -cyclo-octa-1,5-diene) (COD)] with polystyrene under hydrogen atmosphere at room temperature. Elemental analysis, i.r. and mass spectra show that in the above polymer—metal complexes the two cyclo-olefinic ligands, initially present in Ru(COT)(COD), are displaced by the phenyl rings of the polystyrene. Under the same conditions Ru(COT) (COD) reacts with 1, 3-diphenylpropane(DPP) to give, in addition to Ru(η 6 -DPP) (COD), an insoluble product (DPP-Ru 2 ) displaying similar structural properties to the heterogeneous polystyrene complexes. These polystyrene—ruthenium complexes exhibit catalytic activity under rather mild conditions (25-80°C, p H 2 = 50 atm) for the hydrogenation of unsaturated substrates such as olefins, aromatic hydrocarbons, ketones, oximes, and nitro derivatives. Aliphatic and aromatic nitriles can also be converted into amino derivatives at 120 - 140 °C and 50 atm of hydrogen. Experiments carried out with nitrobenzene have shown that the nitro group can be selectively hydrogenated depending on reaction conditions. Insolubility in reaction medium, stability under reaction conditions, and easy separability from products allow re-use of these catalytic systems without appreciable loss of activity.

Preparation and resolution of chiral areneruthenium(II) complexes

Abstract The synthesis of the chiral complexes [RuCl 2 (η n6 -C 6 H 5 CHMeR) 2 ], (R = Et, 1 , t Bu, 2 ), is reported. 1 was prepared from RuCl 3 ·3H 2 O and 1-(2-butyl)- 1,4-cyclohexadiene, whereas 2 was obtained starting from [Ru(η 6 -naphthalene)(η 4 -COD)] (COD = 1,5-cyclooctadiene) and 2,2-dimethyl-3-phenylbutane, which gives [Ru(η 6 -C 6 H 5 CHMe t Bu)(η 4 -COD)] and subsequent reaction with HCl. Complexes 1 and 2 react with (+)-neomenthyldiphenylphosphine (NMDPP) to give monomeric diastereomers [RuCl 2 (η 6 -C 6 H 5 CHMeEt)(NMDPP)] ( 3a , 3b ), and [RuCl 2 (η 6 C 6 H 5 CHMe t Bu)(NMDPP)], ( 4a , 4b ), which were separated by HPLC. The structure of compound 3a was solved by Patterson and Fourier techniques and refined by full-matrix least-squares analysis to R = 0.053, R w = 0.061. The arene is η 6 -bonded to the ruthenium with the phosphorus and the two chlorine atoms arranged as a three legs piano stool. The absolute configuration of the chiral centre of the aromatic ligand in 3a is R . The monomeric diastereomers 3a , 3b , 4a and 4b , were reconverted into their dimeric precursors ( R,R )- 1a , ( S,S )- 1b , ( R,R )- 2a and ( S,S )- 2b as pure enantiomers. The CD spectra of ( R,R )- 1a and ( S,S )- 2b are also reported.

(η6-Cycloocta-1,3,5-Triene)(η4-Cycloocta-1,5-Diene) Ruthenium (0) in the Development of Ruthenium Chemistry

Abstract The simple preparative route to the zero valent (η6-cycloocta-1,3,5-triene) (η4-cycloocta-1,5-diene)ruthenium complex, by reacting RuCl3·3H2O with cycloocta-1,5-diene in the presence of zinc powder, stimulated extensive studies on the chemistry of this compound. Its relevance and versatility as starting material in the preparation of new Ru complexes and as catalytic precursor in organic synthesis are reviewed and discussed.

A simple preparation for (η6-arene)(η4-cyclo-octa-1,5-diene)ruthenium-(0) complexes and their conversion into the corresponding arene–dichlororuthenium(II) complexes

A series of (η6-arene)(η4-cyclo-octa-1, 5-diene)ruthenium(0) complexes have been readily prepared by reaction of (η4-cyclo-octa-1,5-diene)(η6-cyclo-octa-1, 3, 5-triene)ruthenium(0) with arene compounds, under 1 atm H2[arene = C6H6, CH3 C6H5, 1, 4-Me2C6H4, 1,3,5-Me3C6H3, C2H5C6H5, Me2CHC6H5, Et2CHC6H5, C6H5(CH2)3 C6H5,C6H5C6H5, C2H5CH(Me)C6H5, Me2CHCH(Me)C6H5, NH2CH(Me)C6H5, CH3OC6H5, or CH3COC6H5]. These complexes react with aqueous HCI to give in almost quantitative yield the corresponding (η6-arene)-dichlororuthenium(II) complexes.

Arene ligand exchange reactions in (η4-cyclo-octa-1,5-diene)(η6-naphthalene)ruthenium(0): a convenient route to new ruthenium(0) complexes

The reaction of (η4-cyclo-octa-1–5-diene)(η6-cyclo-octa-1,3,5-triene)ruthenium with naphthalene, under H2, affords the complex (η4-cyclo-octa-1,5-diene)(η6-naphthalene)ruthenium which easily undergoes arene exchange reactions in the presence of MeCN.