C–F bond activation of trifluoroethanol and trifluoroacetic acid catalysed by the dimolybdate anion, [Mo2O6(F)]−

Two gas-phase catalytic cycles involving C–F bond activation of trifluoroethanol and trifluoroacetic acid were detected by multistage mass spectrometry experiments. A binuclear dimolybdate centre [Mo 2 O 6 (F)] − acts as the catalyst in each cycle. The first cycle, entered via the reaction of [Mo 2 O 6 (OH)] − with trifluoroethanol and elimination of water to form [Mo 2 O 6 (OCH 2 CF 3 )] − , proceeds via four steps: (1) oxidation of the alkoxo ligand and its elimination as aldehyde; (2) reaction of [Mo 2 O 5 (OH)] − with trifluoroethanol and elimination of water to form [Mo 2 O 5 (OCH 2 CF 3 )]; (3) decomposition of the alkoxo ligand via loss of 1,1 difluoroethene; and (4) reaction of [Mo 2 O 6 (F)] − with a second equivalent of trifluoroethanol to regenerate Mo 2 O 6 (OCH 2 CF 3 )] − . Steps (2) and (3) do not occur at room temperature and require collisional activation to proceed. The second cycle is entered via the reaction of [Mo 2 O 6 (OH)] − with trifluoroacetic acid and elimination of water to form [Mo 2 O 6 (O 2 CCF 3 )] − and involves two steps only: (1) fluoride transfer to a molybdenum centre to form [Mo 2 O 6 (F)] − ; (2) reaction of [Mo 2 O 6 (F)] − with trifluoroacetic acid and loss of water to regenerate [Mo 2 O 6 (O 2 CCF 3 )] − . Comparisons are made with the chemistry of [Mo 2 O 6 (OH)] − reacting with acetic acid.