Molecular halides EXn can act as Lewis acids through E or as Lewis bases through the terminal halogen atoms. Therefore, two different halide E'Ym and EXn can form short life dimers with halogen bridges, that can dissociate into different monomers. The process ultimately leads to a redistribution of the halogen atoms X and Y between two atoms, E and E ', generating the most stable mixture of products possible. The reaction may also occur between a halide and a compound of hydrogen (H/X exchange). See examples.
This reaction occurs through a binuclear species with double halogen bridge.
This reaction is an example of synthesis of fluoride from other halides compounds. The likely mechanism begins with the addition of HF to SiCl4. In this scheme it is assumed that the mechanism involves a state of transition of four centers in which the formation of the Si-F and H-Cl and the breakage of the Si-Cl and H-F bonds are concerted. If there is no perfect synchrony and dominates the approach of hydrogen form HF, the first addition would be close to a proton transfer.