Zirconocene dichloride
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| Identifiers | |||
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| ECHA InfoCard | 100.013.697 | ||
PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |||
| C10H10Cl2Zr | |||
| Molar mass | 292.31 g·mol−1 | ||
| Appearance | white solid | ||
| Soluble (Hydrolysis) | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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 adopts a "clamshell" structure where 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
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]
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 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". Organic Syntheses
{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 9, p. 162.
Further reading
- A. Maureen Rouhi (1998). "Organozirconium Chemistry Arrives". C&EN News. 82 (16): 162. doi:10.1021/cen-v082n015.p035.