Dissecting transmetalation reactions at the molecular level: C-B versus F-B bond activation in phenyltrifluoroborate silver complexes.

The gas-phase unimolecular reactions of the silver(i) complex [Ag(PhBF)], formed via electrospray ionisation mass spectrometry of solutions containing the phenyltrifluoroborate salt and AgNO, are examined. Upon collision induced dissociation (CID) three major reaction channels were observed for [Ag(PhBF)]: Ph group transfer via a transmetalation reaction to yield [PhAg(PhBF)]; F transfer to produce [FAg(PhBF)]; and release of PhBF. The anionic silver product complexes of these reactions, [LAg(PhBF)] (where L = Ph and F), were then mass-selected and subjected to a further stage of CID.

Unimolecular reactivity of organotrifluoroborate anions, RBF , and their alkali metal cluster ions, M(RBF ) (M = Na, K; R = CH , CH CH , CH (CH ) , CH (CH ) , c-C H , C H , C H CH , CH CHCH , CH CH, C H CO).

Rationale: Potassium organotrifluoroborates (RBF K) are important reagents used in organic synthesis. Although mass spectrometry is commonly used to confirm their molecular formulae, the gas-phase fragmentation reactions of organotrifluoroborates and their alkali metal cluster ions have not been previously reported.

Methods: Negative-ion mode electrospray ionization (ESI) together with collision-induced dissociation (CID) using a triple quadrupole mass spectrometer were used to examine the fragmentation pathways for RBF (where R = CH , CH CH , CH (CH ) , CH (CH ) , c-C H , C H , C H CH , CH CHCH , CH CH, C H CO) and M(RBF ) (M = Na, K), while density functional theory (DFT) calculations at the M06/def2-TZVP level were used to examine the structures and energies associated with fragmentation reactions for R = Me and Ph.