Sergio A. Moya

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.

Metallic carbonyl complexes containing heterocycles nitrogen ligands: Part VI. Re(I), Mn(I), Mo(0), and W(0) compounds with 4′-phenyl-2,2′:6′,2″-terpyridine☆

Abstract The synthesis and spectroscopic characterization of new transition metal complexes containing the heterocyclic nitrogen ligand 4′-phenyl-2,2′:6′,2″-terpyridine are reported. Complexes of the [XM(CO) 3 (L)] type (M=Re(I), Mn(I), Mo(0), or W(0); X=Br or CO; and L=4′-phenyl-2,2′:6′,2″-terpyridine) were prepared by photosubstitution or by thermolytic reactions. Aspects of the IR, UV–Vis, proton NMR spectra and electrochemistry of the complexes are discussed. Special attention is given to the fact that the heterocyclic nitrogen ligand ph-tpy acts as a bidentate or terdentate chelate in complexes of this type and shows the fluxionality in the coordination. Correlations between redox potentials and spectroscopic measurements indicate the various interactions of the ligand and the metal center, and allow the evaluation of the metal–ligand back-donation.

Soluble ruthenium carbonyl complexes containing new sterically hindered bipyridine ligands

Abstract The synthesis, characterization and reactivity of bipyridyl ruthenium carbonyl complexes of the type Ru(NN)(CO) 2 Cl 2 [where NN = 4,4′- t Bu 2 -2,2′-byy (bpy ∗ , a ); 6,6′-Me 2 -4,4′- t Bu 2 -2,2′-bpy (dmbpy ∗ , b ); 6,6′-Ph 2 -4,4′- t Bu 2 -2,2′-bpy (dpbpy ∗ , c )] is reported together with the synthesis and characterization of Ru(dpphen)(CO) 2 Cl 2 [where dpphen = 2,9-Ph 2 -1, 10-phen, d ]. When NN is bpy ∗ or dmbpy ∗ , the cis -carbonyl, trans -chloro isomer is obtained, whereas when NN is dpbpy ∗ or dpphen the cis -carbonyl, cis -chloro isomer is the predominant product.

Homogeneous reduction of nitrobenzene to aniline under CO/H2O, catalyzed by cis-[Rh(CO)2(amine)2]PF6. The role of the amine effect

Homogeneous catalytic reduction of nitrobenzene to aniline by cis-[Rh(CO)2(amine)2]PF6 (amine = 4-picoline, 3-picoline, 2-picoline, pyridine, 3,5-lutidine or 2,6-lutidine) in aqueous amine 2/8, v/v, P(CO) = 0.9 atm, T = 100°C, [Rh] = 10 mM under water-gas shift reaction conditions is described. The effect of various amines as additives was examined.

Homogeneous catalysis of the water-gas shift reaction by copper complexes in aqueous substituted pyridine solutions

Abstract Homogeneous catalysis of the water-gas shift reaction has been accomplished by the use of solutions of CuCl2 · 2H2O in aqueous pyridine and other substituted pyridine (methyl pyridines or dimethylpyridine) solutions. This system is stable, low active catalyst displaying turnover frequencies for hydrogen production (TF(H2)) of about 6 moles H2 per mole Cu per day for [Cu] = 20 mM, P(CO) = 1.9 atm and T = 120°C.

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.

Rhodium amino complexes [Rh(COD)(Amine)2]PF6 immobilized on poly(4-vinylpyridine) as catalysts in the water gas shift reaction

Catalysts for the water gas shift reaction prepared from Rh(COD)(amine)2 PF6 (COD=1,5-cyclooctadiene, amine=4-picoline, 3-picoline, 2-picoline, pyridine, 3,5-lutidine or 2,6-lutidine) immobilized on poly(4-vinylpyridine) in contact with 80% aqueoux 2-ethoxyethanol for 1×10−4 mol Rh/0.5 g of polymer, P(CO)=0.9 atm at 100 °C, are described. The role of the coordinated amine effect on the catalytic activity was investigated.

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.

Metal carbonyl complexes containing heterocyclic nitrogen ligands: Part IX. MnBr(CO)3(3,3′-R-2,2′-biquinoline) compounds

The fac-MnBr(CO)3(3,3-R-2,2-biquinoline) (R =CH3 and CH3; H and H; CH2CH2 or CH2CH2CH2) compounds were synthesized and characterized. The fac-conformation for the carbonyl complexes was established by IR spectroscopy. Conformational effects were investigated by means of 1 H NMR and UV–Vis spectroscopical and electrochemical properties and these properties were compared with related rhenium compounds.

Water as hydride source in the reduction of nitrobenzene to aniline catalyzed by cis-[Rh(CO)2(2-picoline)2](PF6) in aqueous 2-picoline under CO atmosphere: kinetics study

Abstract The cis-[Rh(CO)2(2-picoline)2](PF6) complex is active for the catalytic reduction of nitrobenzene to aniline in aqueous 2-picoline solution under water gas shift reaction conditions. The catalytic activities for this system were studied as functions of the reaction parameters (P(CO), [Rh]tot, and T). The nitrobenzene reduction rate displays a first-order dependence on CO pressure, P(CO), over the range 0–1.9 atm at 80, 100 and 120°C. The kinetics behavior with respect to P(CO) leads to the proposal that addition of CO to the catalytic species precedes the rate-limiting step. The catalytic activity proved to be non-linear in total rhodium concentration, [Rh]tot, over the range 5–60 mM. This observation was interpreted in terms of the presence of active mononuclear and polynuclear rhodium species in the system, the mononuclear species being the more active for nitrobenzene reduction. In situ FT-IR spectroscopic study confirms the presence of rhodium species with terminal and bridging carbonyls.