Pedro Aguirre

Modulating the luminescence of an iridium(III) complex incorporating a di(2-picolyl)anilino-appended bipyridine ligand with Zn2+ cations

A novel iridium complex incorporating a di(2-picolyl)anilino-appended bipyridine ligand was synthesized and its optical properties studied. The presence of Zn2+ ions specifically perturbs the excited state, giving rise to a blue-shifted absorption and emission, and a shorter luminescence lifetime.

Lewis super-acid catalyzed cyclizations: a new route to fragrance compounds.

This review deals with the application of Lewis super acids such as AlIII, InIII, and SnIV triflates and triflimidates as catalysts in the synthesis of fragrance materials. Novel catalytic reactions involving CC and Cheteroatom bond‐forming reactions, as well as cycloisomerization processes are presented. In particular, SnIV and AlIII triflates were employed as catalysts in the selective cyclization of unsaturated alcohols to cyclic ethers, as well as in the cyclization of unsaturated carboxylic acids to lactones. The addition of thiols and thioacids to non‐activated olefins, both in intra‐ and intermolecular versions, was efficiently catalyzed by InIII derivatives. SnIV Triflimidates catalyzed the cycloisomerization of highly substituted 1,6‐dienes to gem‐dimethyl‐substituted cyclohexanes bearing an isopropylidene substituent. The hydroformylation of these unsaturated substrates, catalyzed by a RhI complex with a bulky phosphite ligand, selectively afforded the corresponding linear aldehydes. The olfactory evaluation of selected heterocycles, carbocycles, and aldehydes synthesized is also discussed.

RUTHENIUM (II) COMPLEXES IN CATALYTIC OXIDATION

Abstract Ruthenium (II) complexes of the type RuL(CO)2Cl2, [RuL(CO)2L− 2]2+ and [RuL(CO)2Cl L′]+ [L = bipyridine (bpy), phenanthroline (phen), biquinoline (biq) and L′ = pyridine (py), 4-chloropyridine (Cl-py), 4-methoxypyridine (MeO-py)] were synthesized from [Ru(CO)2Cl2]n and L, to produce the intermediate RuL(CO)2Cl2 followed by hydrolysis and reaction with L′. The catalytic activity of these complexes in epoxidation of olefins with iodosylbenzene under ambient conditions was investigated. A possible mechanism of these reactions, explaining the effects of the ligands on the reaction was explored. At least one carbonyl ligand remained bound to the metal through the reaction. The formation of an oxo intermediate was inferred from spectroscopic detection of bridged oxygen Ru—O—Ru and Ru=O species.

Complexes with heterocyclic nitrogen ligands—III. Cationic rhodium(I) derivatives and applications in catalysis☆

Abstract The preparation and spectroscopic properties of mononuclear cationic complexes of rhodium(I) coordinated to the diolefin 2,5-norbornadiene (NBD) and to the heterocyclic nitrogen ligands 6,7-dihydrodipyrido-[2,3-b:3′,2′-j]-1,10-phenanthroline ( 2-4N ), 7,8-dihydro-6H-cyclohepta-[2,1-b:3,4-b]-di-1,8-naphthyridine ( 3–4N ) and 2,2′-bi-(3-methyl)1,8-naphthyridine ( Me-4N ) are described. The complexes show the characteristic intraligand bands of the ligands and an electronic low energy band insensitive to solvent changes and of low intensity, which may be assigned to a ligand field band. The NMR properties agreed with the IR results showing the equivalence of the two naphthyridine fragments in the complexes. Electrochemically all the complexes display two reductions and one oxidation waves, in the potential region from +1.5 to −2.4 V vs Fc + /Fc. The water gas shift reaction (WGSR) and the selective reduction of nitrobenzene to aniline under WGSR conditions are effectively catalysed by these complexes.

Kinetics of the Water Gas Shift Reaction Catalyzed by [Rh(COD)(4-Picoline)2]PF6 Immobilized On Poly(4-vinylpyridine)

Estudios cineticos de la reaccion de desplazamiento del gas de agua se llevaron a cabo en presencia del complejo [Rh(COD)(4-picolina)2]PF6, (COD = 1,5-ciclooctadieno) como catalizador, inmovilizado en poli(4-vinilpiridina) entrecruzado con 2% de divinilbenceno en contacto con una mezcla de 80% de 2-etoxietanol acuoso. El complejo de rodio fue anclado a los grupos piridinicos del polimero organico. Los analisis de los resultados de los estudios cineticos muestran que la reaccion en el sistema heterogenizado sigue una dependencia de primer orden con respecto a la presion de monoxido de carbono, una dependencia no lineal con respecto a la concentracion de rodio total y muestra una curva de Arrhenius segmentada. Estos resultados son discutidos en terminos de un posible mecanismo

AMINOCARBONYLATION REACTION USING PALLADIUM COMPLEXES CONTAINING PHOSPHORUS-NITROGEN LIGANDS AS CATALYSTS

The catalytic activities of palladium complexes containing phosphorus-nitrogen ligands is reported. The catalysts studied showed high activities in the aminocarbonylation of aryl iodides. The palladium complexes reported activities between 100% and 58% in the aminocarbonylation reaction. The reactions are very selective for the double carbonylative amination of aryl halides. The major product is N,N-diethyl-α-oxo benzeneacetamide (96/4). The reaction was made under mild conditions of temperature and carbon monoxide pressure.

REPPE REACTION CATALYZED BY SOLUBLE CARBONYLRHODIUM COMPLEXES

The catalysis of the hydroesterification and hydroformylation-acetalization of 1-hexene by rhodium(I), cis-[Rh(CO)2(amine)2](PF6) complexes (amine = pyridine, 2-picoline, 3-picoline, 4-picoline, 3,5-lutidine or 2,6-lutidine) dissolved in 10 mL of ethanol or 10 mL of 80% aqueous ethanol, 0.4 mL (3 x 10-3 mol) of 1-hexene, [Rh] = 5 x 10-5 mol, 1-hexene/Rh = 64 under P(CO) = 0.9 atm at 100 °C for 4 h, is described in this work. The mayor products are ethyl-heptanoate, heptanal and 1,1-diethoxyheptane coming from the hydroesterification, hydroformylation reactions and the nucleophilic addition reaction of the ethanol over the formed heptanal, respectively. The reaction product distribution depends on the nature of the coordinate amine to the rhodium center

Chiral discrimination in diasteroisomeric systems of cadmium with 1,10-phenanthroline and S-amino acidates

Abstract Δ,Λ-[Cd(phen) 2 (S-aa)] + NO − 3 diastereomeric systems (where phen = 1,10-phenanthroline and S-aa = S -alaninate, S -serinate, S -threoninate, S -prolinate, S -valinate, S -leucinate and S -phenylalaninate) have been prepared in the form of methanolic solutions and characterized by spectral (UV, CD, ORD) and conductance measurements. The CD spectra of these systems in the β′ band region of the diimine ligand exhibit residuary exciton splittings, whose intensities and sign patterns suggest the following decreasing order of [Λ]/[Δ] diastereoisomeric equilibrium constants: S -prol > S -phenala > S -val > 1 > S -ala > S -leu > S -ser > S -threo. The same order is inferred from the ORD data over the range 400–600 nm. Comparison with the selectivities observed for some zinc analogues and the analysis of molecular models suggest that in the cadmium systems the chiral discriminations are governed mainly by a balancing between intramolecular steric repulsion, differential solvation and discriminating ion association. Solvent effects on the optical activity of some cadmium and zinc systems in methanol/n-propanol and methanol/benzene mixtures have also been studied. The corresponding results are discussed in terms of the contributions of the above discriminating forces.

SYNTHESIS, CHARACTERIZATION AND PRELIMINARY CATALYTIC PROPERTIES OF NEW COPPER (I) COMPLEXE [Cu (pyrazolyl)2]X TYPE

AbSTRACT The preparation of tetracoordinated copper (I) complexes with the pyrazolyl heterocyclic nitrogen ligand is reported. The new complexes of [Cu(pyrazolyl) 2 ]X type with X = chloride, bromine, and iodine were characterized by spectroscopic and electrochemical techniques. The results obtained show that the heterocyclic nitrogen ligand is bonded in a bidentate fashion to form monometallic complexes. Exploratory homogeneous catalysis experiments of the water-gas shift reaction (WGSR) have been accomplished by the use of copper complexes in 80 % aqueous 4-picoline solutions. For such systems, formation of H 2 y CO 2 was observed in the initial gas samples. Keywords: Copper Complexes, Heterocyclic Nitrogen Ligand, Pyrazolyl Ligand, WGSR. e-mail: p.aguirre@ciq.uchile.cl INTROduCTION Copper species are widely present in Nature as mono- or multinuclear metal complexes and play a crucial role in different enzymes and catalytic systems, leading to a currently growing interest in the development of new copper models

Synthesis and characterization of ruthenium(II) complexes incorporating 4′-phenyl-terpyridine and triphenylphosphine

The syntheses of two new series of ruthenium(II) complexes incorporating substituted 4′-phenyl-terpyridine, triphenylphosphine, and chloride (A Series) or hydride (B Series) are reported. In both series 4′-phenyl-terpyridine incorporated substituents of varying electronic character at the 4-position: 4′-(4-chlorophenyl)-2,2′ : 6′,2″-terpyridine (ClPh-tpy); 4′-(4-nitrophenyl)-2,2′ : 6′,2″-terpyridine (NO2Ph-tpy) and 4′-(4-methoxyphenyl)-2,2′ : 6′,2″-terpyridine (OMePh-tpy). The complexes have been characterized by elemental analysis and UV–vis, IR, and NMR spectroscopy and their electrochemical properties studied. The substituents on the 4′-phenyl-terpyridine ligand influence the properties of the metal center. For all complexes prepared, λmax of a characteristic low energy band in the UV–vis spectrum was found to move to shorter wavelengths as the solvent polarity increased (a hypsochromic shift). For the B series complexes, the low energy band was broader and undergoes a small shift to lower frequencies as a result of the substitution of chloride by a hydride. The 1H and 31P NMR spectra clearly indicate that the geometry of the 4′-phenyl-terpyridine ligand is meridional in the complexes, with the two triphenylphosphines trans to each other. Upon optimization of the experimental procedures the yields increased to 70% for the B series complexes.