Structure of the Decamethyl Titanocene Cation, a Metallocene with Two Agostic C−H Bonds, and Its Interaction with Fluorocarbons^†

The tetraphenylborate salt of the decamethyl titanocene cation, [Cp*2Ti][BPh4] (1, Cp* = C5Me5), was prepared by reaction of Cp*2TiH with [Cp2Fe][BPh4] and by reaction of Cp*2TiMe with [PhNMe2H][BPh4]. The crystal structure of 1 shows that the Cp*2Ti cation has a bent metallocene structure with agostic interactions with the metal center of two adjacent methyl groups on one of the Cp* ligands. Compound 1 reacts readily with THF to give the adduct [Cp*2Ti(THF)][BPh4] (2). In fluorobenzene, 1 forms the η-fluorobenzene adduct [Cp*2Ti(η1-FC6H5)][BPh4] (3), which was structurally characterized. In contrast to the thermal stability of 3, addition of α,α,α-trifluorotoluene to either 1 or 2 results in C−F activation to give Cp*2TiF2 and PhCF2CF2Ph as the main products. This reactivity toward benzylic C−F bonds is also reflected in the reactivity toward the fluorinated borate anions [B(C6F5)4]- and {B(3,5-(CF3)2C6H3]4}-: reaction of Cp*2TiMe with their [PhNMe2H]+ salts results in a stable complex for the former anion, whereas rapid C−F activation is observed for the latter.