authors |
Neves, P; Gago, S; Balula, SS; Lopes, AD; Valente, AA; Cunha-Silva, L; Paz, FAA; Pillinger, M; Rocha, J; Silva, CM; Goncalves, IS |
nationality |
International |
journal |
INORGANIC CHEMISTRY |
keywords |
BOND-VALENCE PARAMETERS; CRYSTAL-STRUCTURE; TRIS(PYRAZOLYL)METHANE LIGANDS; OLEFIN EPOXIDATION; WATER CLUSTER; FRAMEWORK; COORDINATION; FUNCTIONALITY; CHEMISTRY; NETWORKS |
abstract |
The complex [MoO2Cl{HC(3,5-Me(2)pz)(3)}]BF4 (1) (HC(3,5-Me(2)pz)(3) = tris(3,5-dimethyl-1-pyrazolyl)methane) has been prepared and examined as a catalyst for epoxidation of olefins at 55 degrees C using tert-butyl hydroperoxide (TBHP) as the oxidant. For reaction of cis-cyclooctene, epoxycyclooctane is obtained quantitatively within 5 h when water is rigorously excluded from the reaction mixture. Increasing amounts of water in the reaction mixture lead to lower activities (without affecting product selectivity) and transformation of 1 into the trioxidomolybdenum(VI) complex [{HC(3,5-Me(2)pz)(3)}MoO3] (4). Complex 4 was isolated as a microcrystalline solid by refluxing a suspension of 1 in water. The powder X-ray diffraction pattern of 4 can be indexed in the orthorhombic Pnma system, with a = 16.7349(5) angstrom, b = 13.6380(4) angstrom, and c = 7.8513(3) angstrom. Treatment of 1 in dichloromethane with excess TBHP led to isolation of the symmetrical [Mo2O4(mu(2)-O){HC(3,5-Me(2)pz)(3)}(2)}(BF4)(2) (2) and unsymmetrical [Mo2O3(O-2)(2)(mu(2)-O)(H2O){HC(3,5-Me(2)pz)(3)}] (3) oxido-bridged dimers, which were characterized by single-crystal X-ray diffraction. Complex 2 displays the well-known (Mo2O5)(2+) bridging structure where each dioxidomolybdenum(VI) center is coordinated to three N atoms of the organic ligand and one mu(2)-bridging O atom. The unusual complex 3 comprises dioxido and oxidodiperoxo molybdenum(VI) centers linked by a mu(2)-bridging O atom, with the former center being coordinated to the tridentate N-ligand. The dinuclear complexes exhibit a similar catalytic performance to that found for mononuclear 1. For complexes 1 and 2 use of the ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate and N-butyl-3-methylpyridinium tetrafluoroborate as solvents allowed the complexes to be completely dissolved, and in each case the catalyst and IL could be recycled and reused without loss of activity. |
publisher |
AMER CHEMICAL SOC |
issn |
0020-1669 |
year published |
2011 |
volume |
50 |
issue |
8 |
beginning page |
3490 |
ending page |
3500 |
digital object identifier (doi) |
10.1021/ic102456z |
web of science category |
Chemistry, Inorganic & Nuclear |
subject category |
Chemistry |
unique article identifier |
WOS:000290457700042
|
ciceco authors
impact metrics
journal analysis (jcr 2019):
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journal impact factor |
4.825 |
5 year journal impact factor |
4.501 |
category normalized journal impact factor percentile |
92.222 |
dimensions (citation analysis):
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altmetrics (social interaction):
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