Zirconocene dichloride

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Zirconocene dichloride
Zirconocene-dichloride-2D-skeletal.png
Zirconocene-dichloride-from-xtal-3D-balls.png
Identifiers
1291-32-3 YesY
ChemSpider 29081433 N
Jmol 3D model Interactive image
PubChem 10891641
Properties
C10H10Cl2Zr
Molar mass 292.31 g·mol−1
Appearance white solid
Soluble (Hydrolysis)
Hazards
Safety data sheet CAMEO Chemicals MSDS
Related compounds
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).
N verify (what is YesYN ?)
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[edit]

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[edit]

Schwartz's reagent[edit]

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[edit]

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-hydrogen abstraction to give one η2-butene ligand, eliminating the other butyl ligand as butane.[4]

References[edit]

  1. ^ 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. 
  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. doi:10.1107/S0567740874007011
  3. ^ 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 
  4. ^ Negishi, E.; Takashi, T. (1994). "Patterns of Stoichiometric and Catalytic Reactions of Organozirconium and Related Complexes of Synthetic Interest". Accounts of Chemical Research 27 (5): 124. doi:10.1021/ar00041a002. 

Further reading[edit]