Niobocene dichloride

Structural formula
General
Surname	Niobocene dichloride
other names	Dichlorobis (cyclopentadienyl) niobium Cp 2 NbCl 2
Molecular formula	C 10 H 10 Cl 2 Nb
Brief description	dark brown solid
External identifiers / databases
CAS number 12793-14-5 EC number 631-385-9 ECHA InfoCard 100.159.630 PubChem 24855779 Wikidata Q2023440
properties
Molar mass	293.99 g mol −1
Physical state	firmly
solubility	soluble in toluene
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 315-319-335 P: 261-305 + 351 + 338
Toxicological data	35 mg kg −1 ( LD 50 ,  mouse ,  ip )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Niobocene dichloride or, according to the IUPAC nomenclature, dichlorobis ( η ⁵ - cyclopentadienyl ) niobium (IV) , is an organometallic compound from the family of metallocenes . Like the corresponding vanadium compound, niobocene dichloride is also a 17-electron complex and, due to its unpaired electron, is paramagnetic . In the molecule are the two cyclopentadienyl - and the two chloride - ligand distorted tetrahedral around the central niobium atom located. The dark brown solid is the starting compound for the synthesis of other organoniobes.

Extraction and presentation

Niobocene dichloride was first reported by Geoffrey Wilkinson . It can e.g. B. can be synthesized in a multi-stage reaction starting from niobium pentachloride and cyclopentadienyl sodium :

${\displaystyle \mathrm {NbCl_{5}+\ 6\ Na(C_{5}H_{5})\ {\xrightarrow[{}]{}}\ Nb(C_{5}H_{5})_{4}+\ 5\ NaCl+\ organischeProdukte} }$

${\displaystyle \mathrm {Nb(C_{5}H_{5})_{4}+\ 2\ HCl+0.5\ O_{2}\ {\xrightarrow[{}]{}}\ [((C_{5}H_{5})_{2}NbCl)_{2}O]Cl_{2}+\ 2\ C_{5}H_{6}} }$

${\displaystyle \mathrm {[((C_{5}H_{5})_{2}NbCl)_{2}O]Cl_{2}+\ 2\ HCl+SnCl_{2}\ {\xrightarrow[{}]{}}\ (C_{5}H_{5})_{2}NbCl_{2}+\ SnCl_{4}+\ H_{2}O} }$

properties

In contrast to the metallocenes, the cyclopentadienyl rings in niobocene dichloride are not arranged coplanar , but are angled to one another. The average Cp-M-Cp angle in metallocene dichlorides is usually 130.3 °. The Cl-Nb-Cl angle is 85.6 °, which is smaller than the angle in zirconocene dichloride (97.1 °), but larger than that in molybdocene dichloride (82 °). This trend can be explained by the orientation of the HOMO in this class of compounds.

use

In contrast to the corresponding zirconocene derivatives and the titanocene dichloride , no technical application has been found for niobocene dichloride, although it has been the subject of numerous studies. So it was z. B. examined as a potential cancer drug.

Individual evidence

1. ↑ ^{a b c d e} data sheet bis (cyclopentadienyl) niobium (IV) dichloride from Sigma-Aldrich , accessed on June 18, 2014 ( PDF ).
2. ^ William M. Haynes: CRC Handbook of Chemistry and Physics, 93rd Edition . CRC Press, 2012, p. 78 ( limited preview in Google Book search).
3. ↑ G. Wilkinson, JG Birmingham: Bis-cyclopentadienyl Compounds of Ti, Zr, V, Nb and Ta . In: J. Am. Chem. Soc. tape 76 , no. 17 , 1954, pp. 267–270 , doi : 10.1021 / ja01646a008 .
4. ↑ CR Lucas: Dichlorobis (η5-Cyclopentadienyl) Niobium (IV) . In: Inorganic Syntheses . tape 28 , 1990, pp. 267-270 , doi : 10.1002 / 9780470132593.ch68 .
5. ↑ K. Prout, TS Cameron, RA Ford, SR Critchley, B. Denton, GV 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-cyclopentoniadienyldichloro f) bis-π-cyclopentadienyldichloromolybdenum (V) tetrafluoroborate, (g) μ-oxo-bis [bis-π-cyclopentadienylchloroniobium (IV)] tetrafluoroborate, (h) bis-π-cyclopentadienyldichlorozirconium . In: Acta Cryst. B30, 1974, p. 2290-2304 , doi : 10.1107 / S0567740874007011 .
6. ↑ G. Mokdsi, MM Harding: A ¹ H NMR study of the Interaction of Antitumor Metallocenes with Glutathione . In: J. Inorg. Biochem. tape 86 , no. 2–3 , 2001, pp. 611-616 , doi : 10.1016 / S0162-0134 (01) 00221-5 .