Molybdenum(III) chloride is the inorganic compound with the formula MoCl<sub>3</sub>. It forms purple crystals.
Molybdenum(III) chloride is synthesized by the reduction of molybdenum(V) chloride with hydrogen. A higher yield is produced by the reduction of pure molybdenum(V) chloride with anhydrous tin(II) chloride as the reducing agent.
Molybdenum trichloride exists as two polymorphs: alpha (ñ) and beta (ò). The alpha structure is similar to that of aluminum chloride (AlCl<sub>3</sub>). In this structure, molybdenum has octahedral coordination geometry and exhibits cubic close-packing in its crystalline structure. The beta structure, however, exhibits hexagonal close packing.
Molybdenum trichloride gives a ether complexes MoCl<sub>3</sub>(thf)<sub>3</sub> and MoCl<sub>3</sub>(Et<sub>2</sub>O)<sub>3</sub>. They are beige, paramagnetic solids. Both feature octahedral Mo centers. The diethyl ether complex is synthesized by reducing a Et<sub>2</sub>O solution of MoCl<sub>5</sub> with tin powder. Older procedures involve stepwise reduction involving isolation of the Mo(IV)-thf complex.
Hexa(tert-butoxy)dimolybdenum(III) is prepared by the salt metathesis reaction from MoCl<sub>3</sub>(thf)<sub>3</sub>: