Well-defined alkylpalladium complexes with pyridine-carboxylate ligands as catalysts for the aerobic oxidation of alcohols

Neophylpalladium complexes of the type [Pd(CH(2)CMe(2)Ph)(N-O)(L)], where N-O is picolinate or a related bidentate, monoanionic ligand (6-methylpyridine-2-carboxylate, quinoline-2-carboxylate, 2-pyridylacetate or pyridine-2-sulfonate) and L is pyridine or a pyridine derivative, efficiently catalyze the oxidation of a range of aliphatic, benzylic and allylic alcohols with oxygen, without requiring any additives. A versatile method is described which allows the synthesis of the above-mentioned complexes with a minimum synthetic effort from readily available materials. Comparison of the rates of oxidation of 1-phenylethanol with different catalysts reveals the influence of the structure of the bidentate N-O chelate and the monodentate ligand L on the catalytic performance of these complexesGobierno de España CTQ2009-11721Junta de Andalucía FQM627

Palladium(II) carboxylates and palladium(I) carbonyl carboxylate complexes as catalysts for olefin cyclopropanation with ethyl diazoacetate

Palladium(I) carbonyl carboxylate complexes [Pd(μ-CO)(μ-RCO2)]n (R = Me, n = 4; R = CMe3, n = 6) and the corresponding palladium(II) carboxylates (acetate and pivalate) catalyze the cyclopropanation of olefins with ethyl diazoacetate. The performance of these catalysts is similar in terms of selectivity and cyclopropane yields, regardless of the oxidation state of the metal center. However the rates of the cyclopropanation reactions are significantly higher for the acetate based catalysts than for the pivalate derivatives, which suggests that the main catalytic species are carboxylate containing palladium complexes. Kinetic measurements show that reaction rates are independent of the olefin concentration when these are 1-hexene or styrene, but norbornene exerts an inhibitory effect. In spite of this, competition experiments indicate that the cyclopropanation of styrene is 2.2 times as favorable as that of 1-hexene for any of the four catalysts. These observations indicate that while the rate-determining formation of the intermediate palladium carbenoid species is controlled by the catalyst structure, this is followed by a rapid and less specific cyclopropanation step that is not affected by the nature of the carboxylategroups present in the catalyst. An independent test using a 1:1 benzene/cyclohexane mixture of solvents showed that the transfer of ethoxycarbonylcarbene (:C(CO2Et)H) to these molecules is unselective (relative rate of benzene/cyclohexane functionalization ≈1.8, independent of the catalyst). This result can be interpreted as an indication of the involvement of free ethoxycarbonylcarbene in the carbene transfer step.Russian Foundation for Basic Research 2008RU0055/09-03-91284Junta de Andalucía P06-FQM-0170

Procedimiento de oxidación de alcoholes con oxígeno en presencia de un catalizador homogéneo de paladio

Procedimiento de oxidación de un alcohol con oxígeno en presencia de un catalizador homogéneo, caracterizado porque dicho catalizador homogéneo es un complejo de paladio de fórmula I, o un dímero de éste de formula II, ****IMAGEN**** donde: D-(E)n-X es un ligando de naturaleza bidentada y monoaniónica, donde D es un grupo donador de un par de electrones de tipo dativo, X es un grupo donador covalente no dativo que porta carga aniónica, E es un grupo espaciador y n es un valor seleccionado del grupo que consiste en 0 y 1; Rsi es un ligando aniónico dador de 2 electrones que se enlaza al metal a través de, un único enlace de tipo σ que se selecciona del grupo que consiste en alquilo, arilo, alcóxido, fenóxido, acilo e iminoacilo; y L es un ligando dador de dos electrones neutro que se selecciona dentro del grupo que consiste en una base nitrogenada heterocíclica, un derivado de fósforo III, una base nitrogenada acíclica y un carbeno heterocíclico. Así como los complejos de fórmula I y II y sus procedimientos de obtención.Peer reviewedConsejo Superior de Investigaciones Científicas (España)A1 Solicitud de patente con informe sobre el estado de la técnic

Well-defined alkylpalladium complexes with pyridine-carboxylate ligands as catalysts for the aerobic oxidation of alcohols

Neophylpalladium complexes of the type [Pd(CH(2)CMe(2)Ph)(N-O)(L)], where N-O is picolinate or a related bidentate, monoanionic ligand (6-methylpyridine-2-carboxylate, quinoline-2-carboxylate, 2-pyridylacetate or pyridine-2-sulfonate) and L is pyridine or a pyridine derivative, efficiently catalyze the oxidation of a range of aliphatic, benzylic and allylic alcohols with oxygen, without requiring any additives. A versatile method is described which allows the synthesis of the above-mentioned complexes with a minimum synthetic effort from readily available materials. Comparison of the rates of oxidation of 1-phenylethanol with different catalysts reveals the influence of the structure of the bidentate N-O chelate and the monodentate ligand L on the catalytic performance of these complexesPeer reviewe

Palladium(II) carboxylates and palladium(I) carbonyl carboxylate complexes as catalysts for olefin cyclopropanation with ethyl diazoacetate

8 páginas, 2 figuras, 3 tablas, 4 esquemas.Palladium(I) carbonyl carboxylate complexes [Pd(μ-CO)(μ-RCO2)]n (R = Me, n = 4; R = CMe3, n = 6) and the corresponding palladium(II) carboxylates (acetate and pivalate) catalyze the cyclopropanation of olefins with ethyl diazoacetate. The performance of these catalysts is similar in terms of selectivity and cyclopropane yields, regardless of the oxidation state of the metal center. However the rates of the cyclopropanation reactions are significantly higher for the acetate based catalysts than for the pivalate derivatives, which suggests that the main catalytic species are carboxylate containing palladium complexes. Kinetic measurements show that reaction rates are independent of the olefin concentration when these are 1-hexene or styrene, but norbornene exerts an inhibitory effect. In spite of this, competition experiments indicate that the cyclopropanation of styrene is 2.2 times as favorable as that of 1-hexene for any of the four catalysts. These observations indicate that while the rate-determining formation of the intermediate palladium carbenoid species is controlled by the catalyst structure, this is followed by a rapid and less specific cyclopropanation step that is not affected by the nature of the carboxylategroups present in the catalyst. An independent test using a 1:1 benzene/cyclohexane mixture of solvents showed that the transfer of ethoxycarbonylcarbene (:C(CO2Et)H) to these molecules is unselective (relative rate of benzene/cyclohexane functionalization ≈1.8, independent of the catalyst). This result can be interpreted as an indication of the involvement of free ethoxycarbonylcarbene in the carbene transfer step.Financial support by CSIC and the Russian Foundation for Basic Research (Project 2008RU0055/09-03-91284) is gratefully acknowledged. We also thank the Junta de Andalucía (Project P06-FQM-01704) for additional support.Peer reviewe

Gold(III) Complexation in the Presence of the Macropolyhedral Hydridoborate Cluster [B20H18]2−

Gold(III) complexation with the octadecahydrido-eicosaborate anion [B20H18]2− was studied for the first time. It was found that when gold(III) complexes [Au(L)Cl2]BF4 (L = bipy, phen) reacted with [B20H18]2−, complexes [Au(L)Cl2]2[B20H18] were isolated. The compounds consisted of a cationic gold(III) complex [Au(L)Cl2]+ and the hydridoborate cluster as a counterion. X-ray diffraction studies revealed weak B–H...Au interactions for both compounds. Note that more reactive anions [BnHn]2− (n = 10, 12) in similar reactions with gold(III) complexes resulted in gold mirror reactions