Metal Heptafluoroisopropyl (M-hfip) Complexes for Use as hfip Transfer Agents

Abstract

New coinage-metal heptafluoroisopropyl (LnM-hfip) complexes are synthesized from the metal fluoride and inexpensive hexafluoropropene (M = Ag, Cu; L = PPh3, 2,2,6,6-tetramethylpiperidine (Htmp)). Reaction of the silver Htmp complex with a Ni dibromide complex led to efficient hfip transfer to afford L2NiBr(hfip) (L = 2-ethylpyridine). Treatment of the Ni-hfip complex with ZnPh2 gave the corresponding L2NiPh(hfip) complexes, which were investigated for reductive elimination of PhCF(CF3)2. Although the desired reductive elimination proved unsuccessful, addition of carbon monoxide to L2NiPh(hfip) effected an efficient heptafluoroisopropyl carbonylative cross-coupling. Further, while the silver complex does not undergo hfip transfer to organic electrophiles, the copper complex (phen)(PPh3)Cu(hfip) (3b) effectively transfers the hfip unit to various substrates. We investigated the scope of 3b with acid chlorides toward the synthesis of perfluoroisopropyl aryl ketones. Additionally, reaction conditions for hfip transfer to p-fluorobenzyl bromide and p-fluorobenzaldehyde were identified. As a bonus, 3b was easily generated on a gram scale using commercially available copper hydride by taking advantage of a rapid hydrodefluorination to generate “Cu–F” in situ. Aspects of the observed reactivity are supported by DFT calculations.