Molybdocene dichloride explained

Molybdocene dichloride is the organomolybdenum compound with the formula (η⁵-C₅H₅)₂MoCl₂ and IUPAC name dichlorobis(η⁵-cyclopentadienyl)molybdenum(IV), and is commonly abbreviated as Cp₂MoCl₂. It is a brownish-green air- and moisture-sensitive powder. In the research laboratory, it is used to prepare many derivatives.

Preparation and structure

The compound is prepared from molybdocene dihydride by treatment with chloroform:^[1]

(C₅H₅)₂MoH₂ + 2 CHCl₃ → (C₅H₅)₂MoCl₂ + 2 CH₂Cl₂

The compound adopts a "clamshell" structure where the Cp rings are not parallel, the average Cp(centroid)-M-Cp angle being 130.6°. The two chloride ligands are cis, the Cl-Mo-Cl angle of 82° being narrower than in niobocene dichloride (85.6°), which in turn is less than in zirconacene dichloride (92.1°). This trend helped to establish the orientation of the HOMO in this class of complex.^[2]

Uses

Unlike the titanocene and zirconacene derivatives, the molybdocene compounds have yielded no commercial applications.

All metallocene dihalides exhibit some anti-cancer activity,^[3] but these have not yielded useful compounds in the clinic.^[4]

Notes and References

1. Book: Silavwe . Ned D. . Inorganic Syntheses . Castellani . Michael P. . Tyler . David R. . 1992 . Bis(η5-Cyclopentadienyl)Molybdenum(IV) Complexes . 29 . 204–211 . 10.1002/9780470132609.ch50 . 9780470132609 .
2. K. Prout, T. S. Cameron, R. A. Forder, and in parts S. R. Critchley, B. Denton and G. V. Rees "The crystal and molecular structures of bent bis-π-cyclopentadienyl-metal complexes: (a) bis-π-cyclopentadienyldibromorhenium(V) tetrafluoroborate, (b) bis-π-cyclopentadienyldichloromolybdenum(IV), (c) bis-π-cyclopentadienylhydroxomethylaminomolybdenum(IV) hexafluorophosphate, (d) bis-π-cyclopentadienylethylchloromolybdenum(IV), (e) bis-π-cyclopentadienyldichloroniobium(IV), (f) bis-π-cyclopentadienyldichloromolybdenum(V) tetrafluoroborate, (g) μ-oxo-bis[bis-π-cyclopentadienylchloroniobium(IV)] tetrafluoroborate, (h) bis-π-cyclopentadienyldichlorozirconium" Acta Crystallogr. 1974, volume B30, pp. 2290–2304.
3. Book: Roat-Malone, R. M.. Bioinorganic Chemistry: A Short Course. 2nd. 2007. John Wiley & Sons. 19 - 20. 978-0-471-76113-6.
4. Organometallic Anticancer Agents: Cellular Uptake and Cytotoxicity Studies on Thiol Derivatives of the Antitumor Agent Molybdocene Dichloride. Waern, J. B.. Dillon, C. T.. Harding, M. M.. J. Med. Chem.. 2005. 48. 6. 2093 - 2099. 10.1021/jm049585o. 15771451.