Mononuclear iron silanethiolato complexes of the type CpFe(CO)(2)SSiR3, where R = Ph (1a) and Pr-i (1b), were prepared via treatment of [CpFe(CO)(2)(THF)]BF4 with LiSSiPh3.Et2O and (NaSSiPr3)-Pr-i, respectively. The molecular structure of la was determined by X-ray crystallography. Complex la was reacted with 1 equiv of SO2 to give the corresponding O-silyl thiosulfite, CpFe(CO)(2)SS(O)OSiPh3 (2), via 1,2-insertion Of SO2 into the S-Si bond. This reaction models the activation Of SO2 in the homogeneously catalyzed Claus process.