Infrared Spectra of Matrix-Isolated Antimony and Arsenic Pentafluorides

The infrared spectra of SbF₅ and AsF₅ suspended in argon and neon matrices have been recorded between 4000 and 100 cm⁻¹. The spectra of SbF₅ and AsF₅ are radically different and show that monomeric SbF₅ belongs to symmetry group $C_{\text{4υ}}$ rather than to group $D_{\text{3h}}$ . The spectral effects induced by forming solid SbF₅ from the monomers are understood in terms of associations through Sb–F–Sb fluorine bridge bonds. The behavior is compared with that observed previously for SF₄. No evidence for fluorine bridging occurs with AsF₅.