|
|Section2= |Section7= |Section8= }} 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. It is prepared via a multistep reaction beginning with treatment of niobium pentachloride with cyclopentadienylsodium: :NbCl5 + 6 NaC5H5 → 5 NaCl + (C5H5)4Nb + organic products :(C5H5)4Nb + 2 HCl + 0.5 O2 → ()Cl2 + 2 C5H6 :2 HCl + ()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.〔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() tetrafluoroborate, (h) bis-π-cyclopentadienyldichlorozirconium" Acta Cryst. 1974, volume B30, pp. 2290–2304. 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「niobocene dichloride」の詳細全文を読む スポンサード リンク
|