Infrared Spectra of MF2, MF2+, MF4-, MF3, and M2F6 Molecules (M = Sc, Y, La) in Solid Argon

Reactions of laser-ablated Sc, Y and La atoms with F, in excess argon gave new absorptions in the M-F stretching region, which are assigned to metal fluoride neutral species MF2 and MF3 and ions MF2+ and MF4-. Dibridged MF3 dimers, M2F6, were also identified through terminal M-F and bridge M-F-M stretching modes. Density functional theory (DFT) calculations substantiated the experimental assignments. Mulliken and natural charge distributions indicate significant electron transfer from metal d orbitals to F ligands that increase from Sc to La, suggesting that strong participation of La 5d orbital hybridization drives the F-La-F bond angle below 120 degrees.