resumo
The reaction of [MoO2Cl2(pypzEA)] (1) (pypzEA = ethyl[3-(pyridin-2-yl)-1H-pyrazol-1-yl]acetate) with water in a Teflon-lined stainless steel autoclave (100 degrees C) or in an open reflux system leads to the isolation of the molybdenum oxide/pyrazolylpyridine composite material [Mo2O6(HpypzA)] (2; HpypzA = [3-(pyridinium-2-yl)-1H-pyrazol-1-yl]-acetate). The solid state structure of 2 was solved through single crystal and powder X-ray diffraction analyses in conjunction with information derived from FT-IR and C-13 CP MAS NMR spectroscopies and elemental analyses. In the asymmetric unit of 2, two crystallographically distinct Mo6+ centers are bridged by a syn,syn-carboxylate group of HpypzA. The periodic repetition of these units along the a axis of the unit cell leads to the formation of a one-dimensional composite polymer, (1)(infinity)[Mo2O6(HpypzA)]. The outstretched pyrazolylpyridine groups of adjacent polymers interdigitate to form a zipper-like motif, generating strong onset pi-pi contacts between adjacent rings of coordinated HpypzA molecules. The composite oxide 2 is a stable heterogeneous catalyst for liquid-phase olefin epoxidation.
palavras-chave
STATE COORDINATION CHEMISTRY; ORGANIC/INORGANIC HYBRID MATERIAL; HYDROTHERMAL SYNTHESIS; CRYSTAL-STRUCTURES; POLYOXOMOLYBDATE CLUSTERS; CARBOXYLATE COORDINATION; LIGAND INFLUENCES; SUBUNITS; COMPLEXES; CHAINS
categoria
Chemistry
autores
Figueiredo, S; Gomes, AC; Neves, P; Amarante, TR; Paz, FAA; Soares, R; Lopes, AD; Valente, AA; Pillinger, M; Goncalves, IS
nossos autores
Ana Catarina Costa Gomes Alves
Investigador Auxiliar
Anabela Tavares Aguiar Valente
Investigador Principal
Filipe Alexandre Almeida Paz
Investigador Principal
Isabel Maria de Sousa Gonçalves
Professor associado
Martyn Pillinger
Investigador Principal
Patrícia dos Santos Neves
Investigador Auxiliar
Tatiana Ribau Amarante
Investigador Júnioragradecimentos
We are grateful to the Fundacao para a Ciencia e a Tecnologia (FCT), COMPETE, and the European Union for funding through the R&D project No. PDTC/QUI-QUI/098098/2008 (FCOMP-01-0124-FEDER-010785). The FCT is acknowledged for financial support towards the purchase of the single-crystal diffractometer, for Ph.D. grants to S.F. (SFRH/BD/45116/2008) and T.R.A. (SFRH/BD/64224/2009), and for a postdoctoral grant to P.N. (SFRH/BPD/73540/2010). We appreciate the continued support from the Associate Laboratory CICECO (Pest-C/CTM/LA0011/2011).