Molybdenum tetrachloride explained

Molybdenum tetrachloride is the inorganic compound with the empirical formula MoCl4. The material exists as two polymorphs, both being dark-colored paramagnetic solids. These compounds are mainly of interest as precursors to other molybdenum complexes.

Structure

The α polymorph is a polymer. The β polymorph is a hexamer. In both polymorph, the Mo center is octahedral with two terminal chloride ligands and four doubly bridging ligands.[1] In addition to these two binary phases, a number of adducts are know with the formula where L is a Lewis base.

Preparation

α-Molybdenum tetrachloride can be prepared from by dechlorination of molybdenum pentachloride using tetrachloroethene:[2]

2MoCl5 + C2Cl4 → 2MoCl4 + C2Cl6

Heating α-molybdenum tetrachloride in a sealed container in the presence of molybdenum pentachloride induces conversion to the β polymorph.[2]

Reactions

When heated in an open container, molybdenum tetrachloride evolves chlorine, giving molybdenum trichloride;[2]

2MoCl4 → 2MoCl3 + Cl2

The acetonitrile complex adduct can be prepared by reduction of the pentachloride with acetonitrile:[3] [4]

2MoCl5 + 5CH3CN → 2MoCl4(CH3CN)2 + ClCH2CN + HClThe MeCN ligands can be exchanged with other ligands:

MoCl4(CH3CN)2 + 2THF → MoCl4(THF)2 + 2CH3CN

The pentachloride can be reduced to the ether complex MoCl4(Et2O)2 using tin powder. It is a beige, paramagnetic solid.[5]

References

  1. Ulrich Müller. Hexameric Molybdenum Tetrachloride. Angewandte Chemie International Edition in English. 1981. 20. 8 . 692. 10.1002/anie.198106921.
  2. Book: E. L.. McCann III. T. M.. Brown. Inorganic Syntheses . Molybdenum(IV) Chloride. Inorganic Syntheses . 1970. 12. 181. 10.1002/9780470132432.ch31. 9780470132432 .
  3. Book: 10.1002/9781118744994.ch18. Dimolybdenum and Ditungsten Hexa(Alkoxides). 2014. Broderick. Erin M.. Browne. Samuel C.. Johnson. Marc J. A.. Inorganic Syntheses: Volume 36 . Inorganic Syntheses. 36. 95–102. 9781118744994 .
  4. Book: 28 . The Synthesis of Molybdenum and Tungsten Dinitrogen Complexes . 1990 . 10.1002/9780470132593.ch7. Dilworth . Jonathan R. . Richards . Raymond L. . Inorganic Syntheses . Inorganic Syntheses . 33. 9780470132593 .
  5. Book: 10.1002/9781118744994.ch03. Ether Complexes of Molybdenum(III) and Molybdenum(IV) chlorides . Inorganic Syntheses: Volume 36 . 2014 . Maria . Sébastien . Poli . Rinaldo . Inorganic Syntheses. 36 . 15–18 . 9781118744994 .