| Autor: |
Giffin KA; Department of Chemistry and Biomolecular Sciences and Centre for Catalysis Research and Innovation, University of Ottawa , 30 Marie Curie, Ottawa, Ontario K1N 6N5, Canada., Pua LA; Department of Chemistry and Biomolecular Sciences and Centre for Catalysis Research and Innovation, University of Ottawa , 30 Marie Curie, Ottawa, Ontario K1N 6N5, Canada., Piotrkowski S; Department of Chemistry and Biomolecular Sciences and Centre for Catalysis Research and Innovation, University of Ottawa , 30 Marie Curie, Ottawa, Ontario K1N 6N5, Canada., Gabidullin BM; Department of Chemistry and Biomolecular Sciences and Centre for Catalysis Research and Innovation, University of Ottawa , 30 Marie Curie, Ottawa, Ontario K1N 6N5, Canada., Korobkov I; Department of Chemistry and Biomolecular Sciences and Centre for Catalysis Research and Innovation, University of Ottawa , 30 Marie Curie, Ottawa, Ontario K1N 6N5, Canada., Hughes RP; Department of Chemistry, Dartmouth College , 6128 Burke Laboratories, Hanover, New Hampshire 03755, United States., Baker RT; Department of Chemistry and Biomolecular Sciences and Centre for Catalysis Research and Innovation, University of Ottawa , 30 Marie Curie, Ottawa, Ontario K1N 6N5, Canada. |
| Abstrakt: |
Treatment of Ni(0) complexes 1a-e with sub-atmospheric pressures of trifluoroethylene (TrFE) affords hydrofluoronickelacyclopentanes L 2 Ni(C 4 F 6 H 2 ) 2a-e (L = PPh 3 , P(O-o-tol) 3 , PPh 2 Me, PPhMe 2 , PMe 3 ). Fluorine NMR analysis of 2a-e demonstrates predominant formation of three (of the possible six) isomers upon oxidative cycloaddition of TrFE: the cis and trans head-tail isomers and the trans head-head isomer, where the CHF group is defined as the TrFE "head". The respective ratios of L 2 Ni(C 4 F 6 H 2 ) isomers are influenced by the nature of L, with smaller phosphines favoring the thermodynamically preferred (from DFT calculations) trans head-head isomer (cf. 50% with PMe 3 ) and the largest affording small amounts of the tail-tail isomers. Lewis and Brønsted acids induce a surprising double C-F bond activation in 2c-d, affording small functionalized hydrofluoroalkenes. Interestingly, varying the acid employed dictates the organic product obtained from the head-tail isomers: BF 3 ·OEt 2 is selective for 1,1,2,3-tetrafluorocyclobutene, whereas Me 3 SiOTf and N,N-dimethylanilinium bromide yield (Z,E)-1,1,3,4-tetrafluorobutadiene as the major fluorinated product. Reaction intermediates were isolated, and possible pathways are discussed. |
