Room-temperature catalytic hydrodefluorination of pentafluoro-pyridine by zirconocene fluoro complexes and diisobutylaluminumhydride

Mixtures consisting of zirconocene difluorides Cp′2ZrF2Cp′2ZrF2 (Cp′ = substituted or nonsubstituted η5-cyclopentadienyl) as pre-catalysts and diisobutylaluminumhydride i-Bu2AlH as activator were found to be active catalysts in the room-temperature hydrodefluorination (HDF) of fluorinated pyridines. Evaluation of these systems established rac-(ebthi)ZrF2 (1) and Cp2ZrF2 (3) together with i-Bu2AlH as active catalysts in the room-temperature hydrodefluorination (HDF) of pentafluoro-pyridine. The active species for the conversion were the actually formed hydrides [rac-(ebthi)ZrH(μ-H)]2 (2) and [Cp2ZrH(μ-H)]2 (4). The results we obtained (rt, 24 h, turn over number 67) showed a significantly better performance compared to other investigations published before for this HDF reaction.

Mixtures of the zirconocene fluorides rac-(ebthi)ZrF2 or Cp2ZrF2 as pre-catalysts together with i-Bu2AlH as activator are a new system for active catalysts in the room-temperature hydrodefluorination (HDF) of pentafluoro-pyridine under formation of the 2,3,5,6-tetrafluoro-pyridine. The active species for the conversion were the actually formed zirconocene hydrides [rac-(ebthi)ZrH(μ-H)]2 and [Cp2ZrH(μ-H)]2. The results, we obtained (rt, 24 h, turn over number 67), showed a significantly better performance compared to other investigations published before for this HDF reaction with pentafluoro-pyridine. Figure optionsDownload as PowerPoint slide