Defluorination of perfluoropropene using Cp*2ZrH2 and Cp2ZrHF: a mechanism investigation from a joint experimental-theoretical perspective.
Cp*(2)ZrH(2) (1) (Cp* = pentamethylcyclopentadienyl) reacts with perfluoropropene (2) to give Cp*(2)ZrHF (3) and hydrodefluorinated products under very mild conditions. Initial C-F bond activation occurs selectively at the vinylic terminal position of the olefin to exchange fluorine for hydrogen. Subsequent hydrodefluorination leads to the formation of the n-propylhydride complex Cp*(2)ZrH(CH(2)CH(2)CH(3)), which can be cleaved with dihydrogen to give propane and 1. A theoretical study of the reaction of Cp*(2)ZrH(2) (Cp* = cyclopentadienyl) and CF(2)[double bond]CF(CF(3)) has been undertaken. Several mechanisms have been examined in detail using DFT(B3PW91) calculations and are discussed for this H/F exchange: (a) internal olefin insertion/beta-fluoride elimination, (b) external olefin insertion/beta-fluoride elimination, and (c) F/H metathesis from either an inside or outside approach. Of these, the first case is found to be energetically preferred. Selective defluorination at the terminal carbon has been shown to be favored over defluorination at the substituted and allylic carbons.
Clot
Eric
E
Laboratoire de Structure et Dynamique des Systèmes Moléculaires et Solides (UMR 5636), Case Courrier 14, Université Montpellier 2, 34095 Montpellier Cedex 5, France.
Mégret
Claire
C
Kraft
Bradley M
BM
Eisenstein
Odile
O
Jones
William D
WD