is prepared by chlorination of Mo metal but also chlorination of . The unstable hexachloride  is not produced in this way.
 is reduced by acetonitrile to afford an orange acetonitrile complex, . This complex in turn reacts with THF to give , a precursor to other molybdenum-containing complexes.
Molybdenum(IV) bromide is prepared by treatment of  with hydrogen bromide:
The reaction proceeds via the unstable molybdenum(V) bromide, which releases bromine at room temperature.
 is a good Lewis acid toward non-oxidizable ligands. It forms an adduct with chloride to form . In organic synthesis, the compound finds occasional use in chlorinations, deoxygenation, and oxidative coupling reactions.