resumo
The application field of dichloridodioxidomolybdenum (VI) chelate complexes, which have been intensively investigated as catalysts for liquid-phase olefin epoxidation, is broadened to encompass acid catalysis, in particular, alcoholysis and acetalisation reactions. Complex [MoO2Cl2(L)] (1) with L = 4,4'-di-tert-butyl-2,2'-bipyridine was chosen as (pre)catalyst. Depending on the reaction conditions, 1 either remained structurally intact or was transformed into different metal species, the structures of which were determined on the basis of single-crystal X-ray diffraction, spectroscopic techniques (FT-IR and H-1 NMR), and elemental analysis. The first example of a mixed-ligand complex of the type [MoO2X(OR)(L)] (X = halide) is disclosed. This complex is one of only a handful of complexes known to date that exhibit an all-cis configuration instead of the usual cis-oxido, trans-X, cis-L configuration (X = anionic ligand). Mechanistic considerations of the formation of the metal species are made.
palavras-chave
LEWIS-BASE ADDUCTS; RING-OPENING REACTIONS; MOLYBDENUM(VI) DICHLORIDE DIOXIDE; VALENT OXO-MOLYBDENUM; OLEFIN EPOXIDATION; DIOXOMOLYBDENUM(VI) COMPLEXES; THIOCYANATODIOXOMOLYBDENUM(VI) COMPLEXES; STRUCTURAL-CHARACTERIZATION; CYCLOOCTENE EPOXIDATION; EFFICIENT CATALYSTS
categoria
Chemistry
autores
Gomes, AC; Neves, P; Cunha-Silva, L; Valente, AA; Goncalves, IS; Pillinger, M
nossos autores
Ana Catarina Costa Gomes Alves
Investigador Auxiliar
Anabela Tavares Aguiar Valente
Investigador Principal
Isabel Maria de Sousa Gonçalves
Professor associado
Martyn Pillinger
Investigador Principal
Patrícia dos Santos Neves
Investigador AuxiliarProjectos
Use of molecular containers to modify metallocene-based catalysts (PTDC/QEQ-SUP/1906/2012)
agradecimentos
We acknowledge funding by FEDER (Fundo Europeu de Desenvolvimento Regional) through COMPETE (Programa Operacional Factores de Competitividade). National funding through the FCT (Fundacao para a Ciencia e a Tecnologia) within the project FCOMP-01-0124-FEDER-029779 (FCT ref. PTDC/QEQ-SUP/1906/2012, including the research grant with ref. BPD/UI89/4864/2014 to A. C. G.) is thanked. This work was developed in the scope of the projects CICECO - Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT ref. UID/CTM/50011/2013), and REQUIMTE-LAQV (UID/QUI/50006/2013), financed by national funds through the FCT/MEC and co-financed by FEDER under the PT2020 Partnership Agreement. The FCT and the European Union are acknowledged for post-doctoral grants to A. C. G. (SFRH/BPD/108541/2015) and P. N. (SFRH/BPD/73540/2010) co-funded by MCTES and the European Social Fund through the program POPH of QREN. The FCT and CICECO are acknowledged for financial support toward the purchase of the single-crystal diffractometer.