Mechanism of vinylic and allylic carbon-fluorine bond activation of non-perfluorinated olefins using Cp*2ZrH2

CP*2ZrH2 (1) (Cp* = pentamethylcyclopentadienyl) reacts with vinylic carbon-fluorine bonds of CF2=CH2 and 1,1-difluoromethylenecyclohexane (CF2=C6H10) to afford CP*2ZrHF (2) and hydrodefluorinated products. Experimental evidence suggests that an insertion/beta-fluoride elimination mechanism is occurring. Complex 1 reacts with allylic C-F bonds of the olefins, CH2=CHCF3, CH2=CHCF2CF2CF2CF3, and CH2=C(CF3)(2) to give preferentially 2 and CH3-CH=CF2, CH3-CH=CF-CF2CF2CF3, and CF2=C(CF3)(CH3), respectively, by insertion/beta-fluoride elimination. In the reactions of 1 with CH2=CHCF3 and CH2=CHCF2CF2CF2CF3, both primary and secondary alkylzirconium olefin insertion intermediates were observed in the H-1 and F-19 NMR spectra at low temperature. A deuterium labeling study revealed that more than one olefin-dihydride complex is likely to exist prior to olefin insertion. In the presence of excess 1 and H-2, CH2=CHCF3 and CH2=CHCF2CF2CF2CF3 are reduced to propane and (E)-CH3CH2CF=CFCF2CF3, respectively.