학술논문
Polynuclear Gold(I) Catalysts: When One Gold(I) is not Enough
Document Type
Dissertation/Thesis
Author
Source
TDX (Tesis Doctorals en Xarxa)
Subject
Language
English
Abstract
La investigación de nuestro grupo se centra en la invención de nuevos métodos sintéticos usando catalizadores de oro electrófilos. En un intento de aumentar la electrofilia de los complejos de oro(I) decidimos usar fosfinas orto-boronadas como ligandos ambifílicos. Tras la abstracción de halógeno del complejo neutro de oro(I) obtuvimos el primer clúster Au6(I) con ligandos aromáticos geminalmente diaurados, que muestran actividad catalítica en la ciclación de eninos. Dos clústeres adicionales con sustituyentes ciclohexil y 2-furil han sido sintetizados, con la idea de lograr un mayor entendimiento de la influencia de las propiedades electrónicas de la fosfina en la reactividad. Nuestro siguiente enfoque para aumentar la electrofilia de oro(I) fue la aplicación del ligando 2,6-bis(difenilfosfino)piridina como estrategia para obtener complejos polinucleares de oro(I) que presenten interacciones aurofílicas. Como resultado, se encontró que el complejo linear tetranuclear de oro(I) obtenido no solo catalizaba transformaciones de 1,6-eninos sino también activaba acetona y 1,3-dicetonas para formar complejos de oro(I) y enolatos con una geometría rectangular para los centros de oro(I). Además, en la ausencia de acetona o 1,3-dicetonas observamos hidrólisis de los grupos nitrilo que dieron lugar a la formación de nuevos complejos pentanucleares heterometálicos. Estos complejos mostraron una actividad catalítica excelente en la carbonilación de aminas primarias para formar ureas (intermedios en la síntesis de pesticidas, fertilizantes, tintes y complejos farmacéuticos) bajo condiciones suaves de reacción. Cuando la síntesis del complejo linear tetranuclear de oro(I) se realizó en la ausencia de acetonitrilo, se obtuvo un nuevo complejo de Au8 plano y con forma de anillo. Esto representa un importante descubrimiento en la química del oro, abriendo la posibilidad de entender catálisis en superficies de oro a nivel molecular. En el futuro, las propiedades catalíticas de los complejos de oro(I) polinucleares únicos y con diversas formas presentados aquí serán investigados en mayor detalle.
Research in our group focuses on the invention of new synthetic methods using electrophilic gold catalysts. In an attempt to enhance the electrophilicity of the cationic phosphine gold(I) complexes we decided to use ortho-boronatephosphines as ambiphilic ligands. After abstraction of the halogen from the neutral gold(I) complex we obtained the first hexaauriocluster Au6(I) with geminally diaurated aromatic ring ligands, which shows catalytic activity in the cyclization of enynes. Two additional hexanuclear gold clusters bearing cyclohexyl and 2-furyl substituents on the phosphorus atom have been synthesized, aiming for a better understanding of the influence of the phosphine’s electronic properties in the reactivity of the gold(I) clusters. Our next approach to enhance the electrophilicity of the gold(I) center was the application of the 2,6-bis(diphenylphosphino)pyridine as a strategy to obtain polynuclear gold(I) complexes featuring aurophilic interactions. As a result, linear tetranuclear gold(I) complex was found not only to catalyze different skeletal transformations of enynes but also to activate acetone and 1,3-diketones to form tetranuclear enolate gold(I) complexes with a rectangular geometry of the gold(I) centers in the presence of a mild base. Moreover, in the absence of acetone or 1,3-diketones we observed nitrile hydrolysis that lead to the formation of new pentanuclear heterometallic complexes in good yields. These complexes showed moderate to excellent catalytic activity in the carbonylation of primary amines to ureas (intermediates in the synthesis of pesticides, fertilizers, dyes and pharmaceutical compounds) under mild conditions. When the synthesis of linear tetranuclear gold(I) complex was performed in the absence of acetonitrile, an unprecedented planar ring-shaped Au8 complex was obtained. This represents an important breakthrough in gold chemistry, opening the possibility of understanding catalysis on gold surfaces at the molecular level. In the future, the catalytic properties of the unique and multi-shaped polynuclear gold(I) complexes presented herein will be further investigated.
Research in our group focuses on the invention of new synthetic methods using electrophilic gold catalysts. In an attempt to enhance the electrophilicity of the cationic phosphine gold(I) complexes we decided to use ortho-boronatephosphines as ambiphilic ligands. After abstraction of the halogen from the neutral gold(I) complex we obtained the first hexaauriocluster Au6(I) with geminally diaurated aromatic ring ligands, which shows catalytic activity in the cyclization of enynes. Two additional hexanuclear gold clusters bearing cyclohexyl and 2-furyl substituents on the phosphorus atom have been synthesized, aiming for a better understanding of the influence of the phosphine’s electronic properties in the reactivity of the gold(I) clusters. Our next approach to enhance the electrophilicity of the gold(I) center was the application of the 2,6-bis(diphenylphosphino)pyridine as a strategy to obtain polynuclear gold(I) complexes featuring aurophilic interactions. As a result, linear tetranuclear gold(I) complex was found not only to catalyze different skeletal transformations of enynes but also to activate acetone and 1,3-diketones to form tetranuclear enolate gold(I) complexes with a rectangular geometry of the gold(I) centers in the presence of a mild base. Moreover, in the absence of acetone or 1,3-diketones we observed nitrile hydrolysis that lead to the formation of new pentanuclear heterometallic complexes in good yields. These complexes showed moderate to excellent catalytic activity in the carbonylation of primary amines to ureas (intermediates in the synthesis of pesticides, fertilizers, dyes and pharmaceutical compounds) under mild conditions. When the synthesis of linear tetranuclear gold(I) complex was performed in the absence of acetonitrile, an unprecedented planar ring-shaped Au8 complex was obtained. This represents an important breakthrough in gold chemistry, opening the possibility of understanding catalysis on gold surfaces at the molecular level. In the future, the catalytic properties of the unique and multi-shaped polynuclear gold(I) complexes presented herein will be further investigated.