| Sumario: | The ionic metallocene complexes [CpM][BPh] (Cp = CMe) of the trivalent 3d metals Sc, Ti, and V were synthesized and structurally characterized. For M = Sc, the anion interacts weakly with the metal center through one of the phenyl groups, but for M = Ti and V, the cations are naked. They each contain one strongly distorted Cp ligand, with one (V) or two (Ti) agostic C-H...M interactions involving the CpMe groups. For Sc and Ti, these Lewis acidic species react with fluorobenzene and 1,2-difluorobenzene to yield [CpM(F-FCH)][BPh] (M = Sc, n = 2; M = Ti, n = 1) and [CpM(F-1,2 FCH)][BPh], the first examples of ,F-fluorobenzene and ,²F-1 ,2-difluorobenzene adducts of transition metals. With the perfluorinated anion [B(CF)]-, both Sc and Ti form [CpM(²FC6F5)B(C6F5)3] contact ion pairs. The nature of the metal-fluoroarene interaction was studied by density functional theory (DFT) calculations and by comparison with the corresponding tetrahydrofuran (THF) adducts and was found to be predominantly electrostatic for all metals studied.
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