Zirconocene dichloride

Identifiers

CAS Number

1291-32-3^Y

29081433^N

InChI=1S/2C5H5.2ClH.Zr/c2*1-2-4-5-3-1;;;/h2*1-5H;2*1H;/q2*-1;;;+4/p-2^N
Key: QMBQEXOLIRBNPN-UHFFFAOYSA-L^N
InChI=1/2C5H5.2ClH.Zr/c2*1-2-4-5-3-1;;;/h2*1-5H;2*1H;/q2*-1;;;+4/p-2
Key: QMBQEXOLIRBNPN-NUQVWONBAX

SMILES

[cH-]1cccc1.[cH-]1cccc1.[Cl-].[Cl-].[Zr+4]

Properties

Chemical formula

C₁₀H₁₀Cl₂Zr

Molar mass

292.31 g·mol⁻¹

Appearance

white solid

Solubility in water

Soluble (Hydrolysis)

Hazards

Safety data sheet

CAMEO Chemicals MSDS

Related compounds

Titanocene dichloride
Hafnocene dichloride
Vanadocene dichloride
Vanadocene dichloride
Niobocene dichloride
Tanatalocene dichloride
Tungstenoocene dichloride

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

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Infobox references

Zirconocene dichloride is an organozirconium compound composed of a zirconium central atom, with two cyclopentadienyl and two chloro ligands. It is a colourless diamagnetic solid that is somewhat stable in air.

Preparation and structure

Zirconocene dichloride may be prepared from zirconium(IV) chloride-THF complex and sodium cyclopentadienide:

ZrCl₄(THF)₂ + 2 NaCp → Cp₂ZrCl₂ + 2 NaCl + 2 THF

The closely related compound Cp₂ZrBr₂ was first described by Birmingham and Wilkinson.^[1]

The compound is a bent metallocene: the Cp rings are not parallel, the average Cp(centroid)-M-Cp angle being 128°. The Cl-Zr-Cl angle of 97.1° is wider than in niobocene dichloride (85.6°) and molybdocene dichloride (82°). This trend helped to establish the orientation of the HOMO in this class of complex.^[2]

Reactions

Schwartz's reagent

Zirconocene dichloride reacts with lithium aluminium hydride to give Cp₂ZrHCl Schwartz's reagent:

(C₅H₅)₂ZrCl₂ + ¹/₄ LiAlH₄ → (C₅H₅)₂ZrHCl + ¹/₄ "LiAlCl₄"

Since lithium aluminium hydride is a strong reductant, some over-reduction occurs to give the dihydrido complex, Cp₂ZrH₂; treatment of the product mixture with methylene chloride converts it to Schwartz's reagent.^[3]

Negishi reagent

Zirconocene dichloride can also be used to prepare the Negishi reagent, Cp₂Zr(η²-butene) which is used as a source for Cp₂Zr in oxidative cyclisation reactions. This reagent is prepared by treating zirconacene dichloride with n-BuLi leading to replacement of the two chloride ligands with butyl. The dibutyl compound subsequently undergoes beta-hydride elimination to give one η2-butene ligand, eliminating the other butyl ligand as butane.^[4]

References

↑ G. Wilkinson and J. M. Birmingham (1954). "Bis-cyclopentadienyl Compounds of Ti, Zr, V, Nb and Ta". J. Am. Chem. Soc. 76 (17): 4281–4284. doi:10.1021/ja01646a008.
↑ 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. doi:10.1107/S0567740874007011
↑ S. L. Buchwald, S. J. LaMaire, R. B. Nielsen, B. T. Watson, and S. M. King. "Schwartz's Reagent". Org. Synth. ; Coll. Vol. 9, p. 162
↑ Negishi, E.; Holmes, S. J.; Tour, J. M.; Miller, J. A.; Cederbaum, F. E.; Swanson, D. R.; Takahashi, T. (1989). "Metal-promoted cyclization. 19. Novel bicyclization of enynes and diynes promoted by zirconocene derivatives and conversion of zirconabicycles into bicyclic enones via carbonylation". Journal of the American Chemical Society 111 (9): 3336. doi:10.1021/ja00191a035.