Influence of the Diphosphine Coordinated to Molybdenum and Tungsten Triangular M3S4 Cluster Hydrides in the Catalytic Hydrodefluorination of Pentafluoropyridine

Hydrido molybdenum and tungsten(IV) cluster cations of formula [M 3 S 4 H 3 (dppe) 3 ] + (dppe = 1,2-(bis)dimethylphosphinoethane), [ Mo-1 ] + (M = Mo) and [ W-1 ] + (M = W), have been isolated by reacting their halide precursors with borohydride. Synthetic procedures have been optimized by appropri...

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Bibliographic Details
Published in:Journal of cluster science 2015-01, Vol.26 (1), p.199-209
Main Authors: Alfonso, Carmina, Beltrán, Tomás F., Feliz, Marta, Llusar, Rosa
Format: Article
Language:English
Subjects:
Catalysis
Catalysts
Cesium fluorides
Chemistry
Chemistry and Materials Science
Clusters
Fluorides
Fluorine
Hydrogen
Inorganic Chemistry
Ligands
Molybdenum
Nanochemistry
Nitrogen
Original Paper
Physical Chemistry
Single crystals
Solvents
Substitution reactions
Tungsten
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Summary:Hydrido molybdenum and tungsten(IV) cluster cations of formula [M 3 S 4 H 3 (dppe) 3 ] + (dppe = 1,2-(bis)dimethylphosphinoethane), [ Mo-1 ] + (M = Mo) and [ W-1 ] + (M = W), have been isolated by reacting their halide precursors with borohydride. Synthetic procedures have been optimized by appropriate choice of the solvent. Furthermore, [M 3 S 4 F 3 (dppe) 3 ] + fluorido cluster complexes, [ Mo-2 ] + (M = Mo) and [ W-2 ] + (M = W) have been prepared through halogen substitution reactions using an excess of cesium fluoride. The structures of [ Mo-1 ] + and [ Mo-2 ] + have been determined by single crystal X-ray diffraction experiments. These [ M-1 ] + hydrido and [ M-2 ] + fluorido clusters have been used as catalysts and precatalysts, respectively, in the catalytic hydrodefluorination (HDF) of pentafluoropyridine using HSiMe 2 Ph as hydrogen source. The reaction proceeds under microwave and reflux conditions to selectively afford 2,3,5,6-tetrafluoropyridine. The [ W-1 ] + hydrido cluster is the most efficient catalyst with turnover numbers of 124, while the [ Mo-1 ] + hydrido cluster reacts faster. Fluorido [ Mo-2 ] + and [ W-2 ] + complexes provide lower yields and turnover numbers. In general, the molybdenum and tungsten [ M-1 ] + and [ M-2 ] + diphosphino complexes are more efficient than their dmpe (1,2-(bis)dimethylphosphinoethano) analogues and activate pentafluoropyridine under softer conditions. Graphical Abstract
ISSN:1040-7278
1572-8862
DOI:10.1007/s10876-014-0733-1