Photosensitive Tin Sulfur Dioxide Complexes with Unexpected Bonding Modes.

Infrared spectra of the matrix-isolated Sn(η2 -O2 S), Sn(η2 -OSO), Sn(η2 -O2 S)(η1 -OSO), Sn(η2 -O2 S)2, OSn2 (η2 -SO), and Sn(μ2 -O2 )SnS molecules were observed following laser-ablated Sn atom reactions with SO2 during condensation in solid argon. The assignments for the major vibrational modes were confirmed by appropriate S18 O2 and 34 SO2 isotopic shifts and density functional vibrational frequency calculations (B3LYP and BPW91). Interestingly, the mononuclear complexes are interconvertible; that is, irradiation induces the isomerization of Sn(η2 -O2 S) and Sn(η2 -O2 S)(η1 -OSO) to Sn(η2 -OSO) and Sn(η2 -O2 S)2 , respectively, and vice versa on annealing. However, there is no evidence of isomerization reaction in between the binuclear molecules OSn2 (η2 -SO) and Sn(μ2 -O2 )SnS. Bonding in these products is discussed, and the electronic structure changes associated with different bonding types are revealed, which is crucial for the observed photochemical reactions.