Gas-phase reactions of transition-metal ions with hexafluorobenzene: Room-temperature kinetics and periodicities in reactivity

An inductively coupled plasma (ICP) selected-ion flow tube tandem mass spectrometer has been employed in a systematic survey of room-temperature reactions Of C6F6 with 29 transition-metal ions. The atomic ions were produced at ca. 5500 K in an ICP source and were allowed to decay radiatively and to thermalize by collisions with Ar and He atoms prior to reaction, although for some atomic ions, this quenching may be incomplete. Rate coefficients and product distributions were measured for the reactions of first-row atomic ions from Sc+ to Zn+, of second-row atomic ions from Y+ to Cd+ (excluding Tc+), and of third-row atomic ions from La+ to Hg+. Marked differences were observed for reactivities of early and late transition metal cations with regard to both the reaction efficiency and the type of reaction pathway. Remarkable multiple (up to four) fluorine atom abstraction, proceeding close to the collision rate, dominated the chemistry observed with early transition metal cations while simple association of up to two molecules of C6F6 to the metal cation dominated the chemistry of late transition metal cations. Correlations were found between the electronic configuration of the metal cation and the nature of the reaction path and the reaction efficiency. Only the early third-row Hf+, Ta+, and W+ transition-metal ions exhibited some C-C and C-F bond-dissociation channels leading to ring cleavage.