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How a Thermally Unstable Metal Hydrido Complex Can Yield High Catalytic Activity Even at Elevated Temperatures
Author(s) -
Ehm Christian,
Krüger Juliane,
Lentz Dieter
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201601641
Subject(s) - silanes , catalysis , dissociation (chemistry) , chemistry , hydride , metal , photochemistry , electron paramagnetic resonance , bond dissociation energy , yield (engineering) , kinetic energy , inorganic chemistry , medicinal chemistry , organic chemistry , materials science , silane , metallurgy , physics , nuclear magnetic resonance , quantum mechanics
Despite their instability in ethereal solvents, organotitanium hydride catalysts are successfully employed in catalysis at moderate to high temperatures (110 °C), even in the presence of alcohols. It is shown computationally (bond dissociation energy (BDE) analysis and energetic profile for regeneration) and experimentally (EPR studies and kinetic studies), with the specific example of hydrodefluorination (HDF), that despite the long standing belief, regeneration of Ti−H bonds from Ti−F bonds using silanes is endergonic. The resulting low concentration of Ti−H species is crucial for the catalytic stability of those systems. The resting state in the catalysis is a Ti−F species. The most promising silanes for regeneration are not the ones that have the strongest Si−F bond, but the ones that show the largest difference in Si−F and Si−H BDEs.