Synthesis and reactivity of perfluoroferracyclocarbenes

Abstract The hydrodimerization of C2 fluoroalkenes to saturated C4 hydrofluorocarbons proceeds via hydrogenolysis of M-C bonds in perfluorometallacyclopentanes. In previous work, hydrogenolysis of Fe[κ2-(CF2)4-](CO)4 (1) was shown to yield expected product H(CF2)4H as well as H2CF(CF2)3H, presumably due to Cα-F bond activation. In this work we investigate ligand-substituted analogs of 1 with regard to their propensity to undergo Cα-F bond activation to give perfluoroferracyclocarbenes. Specifically, reaction of 1 with triphos affords Fe=[CF(CF2)3-](F)(triphos) (5) which reacts further with NaBPh4 in acetonitrile to afford {Fe=[CF(CF2)3-](NCMe)(triphos)}+(BPh4)− (6; triphos = bis(2-diphenylphosphinoethyl)-phenylphosphine). In contrast, reaction of 1 with terpy’ followed by Me3SiOTf gives [Fe=[CF(CF2)3-](terpy’)(CO)]+(OTf)− (9; terpy’ = 4′-(4-methylphenyl)-2,2′:6′,2′′-terpyridine; OTf = SO3CF3). While 5 does not react readily with H2, 6 is readily converted to [FeH(triphos)(NCMe)]+(BPh4)− (10) and H2CF(CF2)3H whereas 9 undergoes a complex reaction with H2, affording HF and a mixture of uncharacterized Fe organofluorine complexes.