Niobocene dichloride is the

organometallic compound Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and s ...

with the formula (C₅H₅)₂NbCl₂, abbreviated Cp₂NbCl₂. This

paramagnetic Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, ...

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 Sir Geoffrey Wilkinson FRS (14 July 1921 – 26 September 1996) was a Nobel laureate English chemist who pioneered inorganic chemistry and homogeneous transition metal catalysis. Education and early life Wilkinson was born at Springside, Todm ...

. It is prepared via a multistep reaction beginning with treatment of

niobium pentachloride Niobium(V) chloride, also known as niobium pentachloride, is a yellow crystalline solid. It hydrolyzes in air, and samples are often contaminated with small amounts of NbOCl3. It is often used as a precursor to other compounds of niobium. NbC ...

with cyclopentadienylsodium: :NbCl₅ + 6 NaC₅H₅ → 5 NaCl + (C₅H₅)₄Nb + organic products :(C₅H₅)₄Nb + 2 HCl + 0.5 O₂ → sub>2Ol₂ + 2 C₅H₆ :2 HCl + sub>2Ol₂ + 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 Molybdocene dichloride is the organomolybdenum compound with the formula ( η5-C5H5)2MoCl2 and IUPAC name dichlorobis(η5-cyclopentadienyl)molybdenum(IV), and is commonly abbreviated as Cp2MoCl2. It is a brownish-green air- and moisture-sensitive ...

(82°). This trend is consistent with the orientation of the

HOMO ''Homo'' () is the genus that emerged in the (otherwise extinct) genus '' Australopithecus'' that encompasses the extant species ''Homo sapiens'' ( modern humans), plus several extinct species classified as either ancestral to or closely relat ...

in this class of complex.

Applications and further work

Unlike the related zirconacene and

titanocene dichloride Titanocene dichloride is the organotitanium compound with the formula ( ''η''5-C5H5)2TiCl2, commonly abbreviated as Cp2TiCl2. This metallocene is a common reagent in organometallic and organic synthesis. It exists as a bright red solid that slowl ...

s, no applications have been found for this compound, although it has been studied widely. It was investigated as a potential anti-cancer agent.

References

{{Niobium compounds Metal halides Metallocenes Organoniobium compounds Cyclopentadienyl complexes Chloro complexes Niobium(IV) compounds