Niobocene dichloride

Niobocene dichloride
Names
	IUPAC name Dichloridobis (η5-cyclopentadienyl)niobium
	Other names Niobocene dichloride
Identifiers
CAS Number	12793-14-5 ;
ECHA InfoCard	100.159.630
RTECS number	QU0400000;
Properties
Chemical formula	C10H1oCl2Nb
Molar mass	294 g/mol
Appearance	brown solid
Melting point	dec.
Boiling point	dec.
Solubility in water	soluble (hydrolysis)
Solubility in other solvents	sparingly in chlorocarbons
Related compounds
Related compounds	Cp2TiCl2; Cp2MoCl2 Cp2VCl2
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

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]

NbCl₅ + 6 NaC₅H₅ → 5 NaCl + (C₅H₅)₄Nb + organic products

(C₅H₅)₄Nb + 2 HCl + 0.5 O₂ → [{C₅H₅)₂NbCl}₂O]Cl₂ + 2 C₅H₆

2 HCl + [{(C₅H₅)₂NbCl}₂O]Cl₂ + SnCl₂ → 2 (C₅H₅)₂NbCl₂ + SnCl₄ + H₂O

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 zirconacene 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

^ G. Wilkinson and J.G. Birmingham (1954). "Bis-cyclopentadienyl Compounds of Ti, Zr, V, Nb and Ta". J. Am. Chem. Soc. 76 (17): 4281–4284. doi:10.1021/ja01646a008.
^ C. R. Lucas (1990). "Dichlorobis(η5-Cyclopentadienyl)Niobium(IV)". Inorg. Synth. 28: 267–270. doi:10.1002/9780470132593.ch68. ISBN 0-471-52619-3.
^ 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
^ Mokdsi, G.; Harding, M. M. (2001). "A¹H NMR study of the Interaction of Antitumor Metallocenes with Glutathione". J. Inorg. Biochem. 86 (2–3): 611–616. doi:10.1016/S0162-0134(01)00221-5.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[1] G. Wilkinson and J.G. 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] C. R. Lucas (1990). "Dichlorobis(η5-Cyclopentadienyl)Niobium(IV)". Inorg. Synth. 28: 267–270. doi:10.1002/9780470132593.ch68. ISBN 0-471-52619-3.

[3] 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

[4] Mokdsi, G.; Harding, M. M. (2001). "A¹H NMR study of the Interaction of Antitumor Metallocenes with Glutathione". J. Inorg. Biochem. 86 (2–3): 611–616. doi:10.1016/S0162-0134(01)00221-5.{{cite journal}}: CS1 maint: multiple names: authors list (link)

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