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.

Niobocene dichloride

Names
IUPAC name Dichloridobis (η5-cyclopentadienyl)niobium
Other names Niobocene dichloride
Identifiers
CAS Number	12793-14-5 Y
3D model (JSmol)	Interactive image
ChemSpider	21251691
ECHA InfoCard	100.159.630
EC Number	631-385-9
PubChem CID	16211739
RTECS number	QU0400000
InChI InChI=1S/2C5H5.2ClH.Nb/c2*1-2-4-5-3-1;;;/h2*1-5H;2*1H;/q;;;;+2/p-2 Key: CYMWZQTUXXEBCR-UHFFFAOYSA-L
SMILES [cH-]1cccc1.[cH-]1cccc1.Cl[Nb+2]Cl
Properties
Chemical formula	C10H10Cl2Nb
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
Hazards
GHS labelling:[1]
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
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). Y verify (what is YN ?) Infobox references

Preparation and structure

It was originally reported by Geoffrey Wilkinson.^[2] It is prepared via a multistep reaction beginning with treatment of niobium pentachloride with cyclopentadienylsodium:^[3]

NbCl₅ + 5 NaC₅H₅ → 5 NaCl + (C₅H₅)₄Nb + "C₅H₅"

2 (C₅H₅)₄Nb + 4 HCl + 0.5 O₂ → [(C₅H₅)₂NbCl]₂OCl₂ + 4 C₅H₆

[(C₅H₅)₂NbCl]₂OCl₂ + SnCl₂ + 2 HCl → 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 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.^[4]

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.^[5]