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.

本研究报道了首个可分离的二氟卡宾镍配合物（NiP₂[P(OMe)₃](=CF₂)；其中P₂代表Ph₂P(CH₂)₂PPh₂，该配合物含2个P(OMe)₃配体），此类配合物同时也是形式上为d¹⁰电子构型的金属氟卡宾配合物的唯一已知实例。这类[Ni⁰]=CF₂配合物可与四氟乙烯（TFE）反应，生成罕见的全氟金属环丁烷配合物[NiP₂(κ²-CF₂CF₂CF₂⁻)]，该类反应与氟烯烃复分解及聚合反应具有潜在关联。初步动力学实验结果表明，新型[Ni]=CF₂化合物与四氟乙烯的反应速率显著快于此前报道的[Co]=CF₂对应配合物的同类反应。进一步研究发现，向配合物2中加入四氟乙烯的过程为解离过程，这与[Co]=CF₂配合物以缔合方式与四氟乙烯反应的特性截然相反。最后，本文还对[NiP₂(κ²-CF₂CF₂CF₂⁻)]（其中P₂ = Ph₂P(CH₂)₂PPh₂）的初步反应活性进行了描述。