Two new perchlorato complexes. The oxochloro(perchlorato)antimony complexes Sb2Cl6(OH)(O)(ClO4) and Sb8Cl24(O5)(ClO4)6: synthesis, vibrational spectroscopy, and x-ray structural determination of (.mu.-hydroxo)(.mu.-oxo)(perchlorato)bis[trichloroantimony(V)], Sb2Cl6(OH)(O)(ClO4)