Niobocene dichloride
Niobocene dichloride is the organometallic compound with the formula (C5H5)2NbCl2, abbreviated Cp2NbCl2. This paramagnetic brown solid is a starting reagent for the synthesis of other organoniobium compounds. The compound adopts a pseudotetrahedral structure with two cyclopentadienyl and two chloride substituents attached to the metal. A variety of similar compounds are known, including Cp2TiCl2.
Preparation and structure
It was originally reported by Geoffrey Wilkinson.[1] It is prepared via a multistep reaction beginning with treatment of niobium pentachloride with cyclopentadienylsodium:[2]
The compound adopts a "clamshell" structure characteristic of a bent metallocene where the Cp rings are not parallel, the average Cp(centroid)-M-Cp angle being about 130.3°. The Cl-Nb-Cl angle of 85.6° is narrower than in zirconocene dichloride (97.1°) but wider than in molybdocene dichloride (82°). This trend is consistent with the orientation of the HOMO in this class of complex.[3]
Applications and further work
Unlike the related zirconacene and titanocene dichlorides, no applications have been found for this compound, although it has been studied widely. It was investigated as a potential anti-cancer agent.[4]
References
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- ↑ 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. Script error: No such module "CS1 identifiers".
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Template:Niobium compounds Template:Cyclopentadienide complexes