Forming trifluoromethylmetallates: competition between decarboxylation and C-F bond activation of group 11 trifluoroacetate complexes, [CF3CO2ML]-

A combination of gas-phase 3D quadrupole ion trap mass spectrometry experiments and density functional theory (DFT) calculations have been used to examine the mechanism of thermal decomposition of fluorinated coinage metal carboxylates. The precursor anions, [CF3CO2MO2CCF3](-) (M = Cu, Ag and Au), were introduced into the gas-phase via electrospray ionization. Multistage mass spectrometry (MSn) experiments were conducted utilizing collision-induced dissociation, yielding a series of trifluoromethylated organometallic species and fluorides via the loss of CO2, CF2 or CF2CO2. Carboxylate ligand loss was insignificant or absent in all cases. DFT calculations were carried out on a range of potentially competing fragmentation pathways for [CF3CO2MO2CCF3](-), [CF3CO2MCF3](-) and [CF3CO2MF](-). These shed light on possible products and mechanisms for loss of CF2CO2, namely, concerted or step-wise loss of CO2 and CF2 and a CF2CO2 lactone pathway. The lactone pathway was found to be higher in energy in all cases. In addition, the possibility of forming [CF3MCF3](-) and [CF3MF](-), via decarboxylation is discussed. For the first time the novel fluoride complexes [FMF](-), M = Cu, Ag and Au have been experimentally observed. Finally, the decomposition reactions of [CF3CO2ML](-) (where L = CF3 and CF3CO2) and [CH3CO2ML](-) (where L = CH3 and CH3CO2) are compared.