d¹⁰ Nickel Difluorocarbenes and Their Cycloaddition Reactions with Tetrafluoroethylene

We report the first isolable nickel difluorocarbene complexes (NiP2[P­(OMe)3]­(CF2); P2 = Ph2P­(CH2)2PPh2, 2 P­(OMe)3), which are also the only examples of formally d10 metal fluorocarbenes. These [Ni0]CF2 complexes react with tetrafluoroethylene (TFE) to yield the rare perfluorometallacyclobutanes [NiP2(κ2-CF2CF2CF2−)], with potential relevance to fluoroalkene metathesis and polymerization. Preliminary kinetic experiments establish that the reactions of the new [Ni]CF2 compounds with TFE are considerably faster than the analogous reactions of their previously reported [Co]CF2 counterparts. Further, we show that TFE addition to 2 is a dissociative process, in contrast to [Co]CF2, which reacts with TFE in an associative fashion. Finally, the preliminary reactivity of NiP2(κ2-CF2CF2CF2−) (P2 = Ph2P­(CH2)2PPh2) is described.