Metal Azolate/Carboxylate Frameworks as Catalysts in Oxidative and C-C Coupling Reactions.
The five metal azolate/carboxylate (MAC) compounds [Cd(dmpzc)(DMF)(H2O)] (Cd-dmpzc), [Pd(H2dmpzc)2Cl2] (Pd-dmpzc), [Cu(Hdmpzc)2] (Cu-dmpzc), [Zn4O(dmpzc)3]·Solv (Zn-dmpzc·S), and [Co4O(dmpzc)3]·Solv (Co-dmpzc·S) were isolated by coupling 3,5-dimethyl-1H-pyrazol-4-carboxylic acid (H2dmpzc) to cadmium(II), palladium(II), copper(II), zinc(II), and cobalt(II) salts. While Cd-dmpzc and Pd-dmpzc had never been prepared in the past, for Cu-dmpzc, Zn-dmpzc·S, and Co-dmpzc·S we optimized alternative synthetic paths that, in the case of the copper(II) and cobalt(II) derivatives, are faster and grant higher yields than the previously reported ones. The crystal structure details were determined ab initio (Cd-dmpzc and Pd-dmpzc) or refined (Cu-dmpzc, Zn-dmpzc·S, and Co-dmpzc·S) by means of powder X-ray diffraction (PXRD). While Cd-dmpzc is a nonporous 3D MAC framework, Pd-dmpzc shows a 3D hybrid coordination/hydrogen-bonded network, in which Pd(H2dmpzc)2Cl2 monomers are present. The thermal behavior of the five MAC compounds was investigated by coupling thermal analysis to variable-temperature PXRD. Their catalytic activity was assessed in oxidative and C-C coupling reactions, with the copper(II) and cadmium(II) derivatives being the first nonporous MAC frameworks to be tested as catalysts. Cu-dmpzc is the most active catalyst in the partial oxidation of cyclohexane by tert-butyl hydroperoxide in acetonitrile (yields up to 12% after 9 h) and is remarkably active in the solvent-free microwave-assisted oxidation of 1-phenylethanol to acetophenone (yields up to 99% at 120 °C in only 0.5 h). On the other hand, activated Zn-dmpzc·S (Zn-dmpzc) is the most active catalyst in the Henry C-C coupling reaction of aromatic aldehydes with nitroethane, showing appreciable diastereoselectivity toward the syn-nitroalkanol isomer (syn:anti selectivity up to 79:21).
Department of Chemistry, Physics and Environment, Faculty of Sciences and Environment, "Dunarea de Jos" University of Galati , 111 Domneasca Street, 800201 Galati, Romania.
Aurel
A
Tăbăcaru
School of Pharmacy, Chemistry Section, University of Camerino , Via S. Agostino 1, 62032 Camerino, Italy.
Nertil
N
Xhaferaj
Chemical Engineering Department, Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa , R. Conselheiro Emídio Navarro, 1959-007 Lisboa, Portugal.|Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa , Avenida Rovisco Pais, 1049-001 Lisboa, Portugal.
Luísa M D R S
LM
Martins
Chemical Engineering Department, Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa , R. Conselheiro Emídio Navarro, 1959-007 Lisboa, Portugal.|Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa , Avenida Rovisco Pais, 1049-001 Lisboa, Portugal.
Elisabete C B A
EC
Alegria
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa , Avenida Rovisco Pais, 1049-001 Lisboa, Portugal.
Rogério S
RS
Chay
Dipartimento di Scienza e Alta Tecnologia, Università dell'Insubria , Via Valleggio 11, 22100 Como, Italy.|ID22 High-Resolution Powder-Diffraction Beamline, European Synchrotron Radiation Facility , CS 40220, 38043 Grenoble Cedex 9, France.
Carlotta
C
Giacobbe
National Taras Shevchenko University of Kyiv , Volodimirska Strasse 64, 01033 Kyiv, Ukraine.
Konstantin V
KV
Domasevitch
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa , Avenida Rovisco Pais, 1049-001 Lisboa, Portugal.
Armando J L
AJ
Pombeiro
Dipartimento di Scienza e Alta Tecnologia, Università dell'Insubria , Via Valleggio 11, 22100 Como, Italy.
Simona
S
Galli
School of Pharmacy, Chemistry Section, University of Camerino , Via S. Agostino 1, 62032 Camerino, Italy.
Claudio
C
Pettinari