Gallium Hydrides and O/N‐Donors as Tunable Systems in C−F Bond Activation

The gallium hydrides (iBu)₂GaH ( 1 a ), LiGaH₄ ( 1 b ) and Me₃N⋅GaH₃ ( 1 c ) hydrodefluorinate vinylic and aromatic C−F bonds when O and N donor molecules are present. 1 b exhibits the highest reactivity. Quantitative conversion to the hydrodefluorination (HDF) products could be observed for hexafluoropropene and 1,1,3,3,3‐pentafluoropropene, 94 % conversion of pentafluoropyridine and 49 % of octafluorotoluene. Whereas for the HDF with 1 b high conversions are observed when catalytic amounts of O donor molecules are added, for 1 a , the addition of N donor molecules lead to higher conversions. The E/Z selectivity of the HDF of 1,1,3,3,3‐pentafluoropropene is donor‐dependent. DFT studies show that HDF proceeds in this case via the gallium hydride dimer–donor species and a hydrometallation/elimination sequence. Selectivities are sensitive to the choice of donor, as the right donor can lead to an on/off switching during catalysis, that is, the hydrometallation step is accelerated by the presence of a donor, but the donor dissociates prior to elimination, allowing the inherently more selective donorless gallium systems to determine the selectivity.