|Molar mass||292.32 g·mol−1|
|MSDS||CAMEO Chemicals MSDS|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
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
- ZrCl4(THF)2 + 2 NaCp → Cp2ZrCl2 + 2 NaCl + 2 THF
The closely related compound Cp2ZrBr2 was first described by Birmingham and Wilkinson.
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.
- (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.
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.
- 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 Cryst. 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.