The first examples of a new class of main group metallacycles, stibathiolanes, have been synthesized via transmetalation from zirconocene metallacycles. The X-ray crystal structures of three 1-halostibathiolanes have been determined and the compounds found to be polymeric in the crystalline state. Physical and spectroscopic data indicate that the compounds are monomeric in hydrocarbon solution but that they undergo rapid-reversible halide-exchange reactions. A consequence of one of these exchange reactions is the inversion of stereochemistry at antimony. The processes have been investigated by using a variety of NMR and crossover experiments. The proposed intermediate for the inversion of stereochemistry at the metal center is supported by the solid-state structures of the compounds in which the proposed connectivity of the intermediate is crystallographically established.