LAUSR

The AlF2(O2S) and SiF2(O2S) complexes with bidentately coordinated sulfur dioxide ligands were prepared via the reactions of aluminum and silicon atoms with SO2F2 under UV-vis irradiation in cryogenic matrixes. The products were identified by infrared spectroscopy as well as DFT frequency calculations, and nonplanar C2v structures with the SO2 ligand bound to Al/Si via two oxygen atoms were established. In spite of the similarity in geometric structures, the electronic structures of AlF2(O2S) and SiF2(O2S) are completely different. The longer S-O bond length and the lower O-S-O stretching vibrational frequencies of SiF2(O2S) in comparison to those of AlF2(O2S) indicate that SiF2(O2S) possesses a singlet SO22--like ligand while the SO2 ligand is better described as SO2- in AlF2(O2S), which is further confirmed by bonding and population analysis. Linear correlations were established between the experimental O-S-O stretching frequencies and calculated S-O bond lengths of SO2, AlF2(O2S), and SiF2(O2S), suggesting that the S-O bond is gradually activated when SO2 is coordinated to AlF2 and SiF2.