Lithium ferrocenyl

Diferrocenyl Tellurium2 A solution of 0.10 g (0.52 mmol) ferrocenyl lithium in 25 ml tetrahydrofuran is mixed with 0.16 g (0.26 mmol) of diferrocenyl ditellurium. The mixture is stirred at 20° for 1 h. The solvent is evaporated and the residue is dissolved in a small volume of dichloromethane. The solution is chromatographed on a silica gel column. Ferrocene and bifcrroccnc arc washed from the column with pentane. Diferrocenyl tellurium and diferrocenyl tellurium are eluted with dichloromethane. The diferrocenyl tellurium compounds are separated on 0.5 mm silica gel layers with pentane/toluene (7 1) as the mobile phase. The orange crystals melt at 164-166° yield 9%. 

Interaction of ferrocene and diazonium compounds, which is followed by loss of nitrogen, leads to a large number of derivatives 17, HI, 1, 14s, 30S) most of them, naturally, are aryl-substituted compounds. Ferrocene cannot only be mercuriated, but can also be metalled by lithium butyl or similar compounds such as sodium phenyl. A great variety of pt ibilities for substitution is afforded by the interaction of ferrocenyl lithium and halogen-containing compounds 5, 128, 143, 162). Carboxylic acids, in particular, may easily be obtained by formation of the lithium derivative of ferrocene and treatment with carbon dioxide. 

Ferrocenyfamine, Fe(CioH NH2), is obtained by the Kosheshkov reaction from ferrocenyl lithium and the benzyl ether of hydroxylamine... 

The last decade has brought a number of interesting new examples of the Sn reaction in the 1,2,4-triazine series. For instance, 5,6-diphenyl-l,2,4-triazine was found to react with ferrocenyl lithium 93 under oxidative conditions to give the corresponding 3-ferrocenyl-l,2,4-triazine 94 (Scheme 51) <2007EJ0857>. 

The reinvestigation of reactions of [2-(dimethylaniinomethyl)ferrocenyl]lithium (1), (FcN)Li, with silicon tetrachloride has delivered new analytical data for (FcN)SiCl3, especially X-ray structure analysis results showing pentacoordination of the silicon atom [4]. The treatment of silicon tetrachloride with two equivalents of (FcN)lithium (I) results in (FcN>2SiCl2 (2) as a reddish solid (Scheme 1). 

Treatment of anhydrous YbCls with 2-(dimethylaminoethyl)ferrocenyl lithium in a 1 2 molar ratio affords the o-bonded complex 9. The reaction between [Cp2YbCl]2 and LiFcN [LiFcN = CpFe(C5H3LiCH2NMe2)] results in replacement of a cyclopentadienyl group and formation of 10.66... 

We wished to explore the use of asymmetric synthesis for the preparation of faxocenes bearing planar chirality. The main approaches are summarized in Figure 9. We attempted the route I, taking R=CH2NMe2 and using the combination sec-Buli / sparteine as the chiral base. Unfortunately a racemic ferrocenyl lithium compound was formed, as established by some electrophilic quenchings. We recently successfully developed route II (vide infra). 

The most useful ferrocene derivatives for the development of functional ferrocene chemistry are acetylferrocene, ferrocenyl carbaldehyde, ferrocenyl lithium and... 

Fig. 39. The preparation of ferrocene derivatives using ferrocenyl lithium...

Deprotonation of l-methyl-3-ferrocenylimidazolium tetrafluoroborate or iodide (98JOM(552)45) by lithium di-Mo-propylamide and subsequent reaction with W(C0)5-THF gives the carbene complex 107 and bis-carbene 108, even when excess W(CO)j THF is applied (99JOM(572)177). Numerous ferrocenyl benzimidazoles are known (97RCR613, 99JOM(580)26). 

The lithium benzamidinates Li[PhC(NR)2] (R = Cy, Pr ) and Li[2,4,6-(Cp3)3C6H2C(NCy)2] have been prepared analogously. Reaction of FcLi (Fc = ferrocenyl) with 1,3-dicyclohexylcarbodiimide ( = DCC, Scheme 6), followed by addition of water, afforded the ferrocene-substituted amidine Fc(NCy)NHCy in 50% yield. The amidine is readily deprotonated by LLN(SiMe3)2 or NaN(SiMe3)2 to yield the alkali metal amidinates, Li[FcC(NCy)2l and Na[FcC(NCy)2l in high yields. ... 

A reaction of C0CI2 with 2 equivalents of the lithium ferrocenyl amidinate EcC(NCy)2Li(Et20) in THE gave the trimetallic complex [FcC(NCy)2l2Co (Scheme 148, Figure 26) in good yield. ... 

Ferrocenyl organo tellurium derivatives were prepared from diferrocenyl ditellurium and organic lithium compounds with toluene or tetrahydrofuran as the solvent2. 

Planar chiral compounds should also be accessible from the chiral pool. An example (with limited stereoselectivity) of such an approach is the formation of a ferrocene derivative from a -pinene-derived cyclopentadiene (see Sect. 4.3.1.3 [81]). A Cj-symmetric binuclear compound (although not strictly from the chiral pool, but obtained by resolution) has also been mentioned [86]. Another possibility should be to use the central chiral tertiary amines derived from menthone or pinene (see Sect. 4.3.1.3 [75, 76]) as starting materials for the lithiation reaction. In these compounds, the methyl group at the chiral carbon of iV,iV-dimethyl-l-ferrocenyl-ethylamine is replaced by bulky terpene moieties, e.g., the menthane system (Fig. 4-2 le). It was expected that the increase in steric bulk would also increase the enantioselectivity over the 96 4 ratio, as indicated by the results with the isopropyl substituent [118]. However, the opposite was observed almost all selectivity was lost, and lithiation also occurred in the position 3 and in the other ring [134]. Obviously, there exists a limit in bulkiness, where blocking of the 2-position prevents the chelate stabilization of the lithium by the lone pair of the nitrogen. 

Neither diferrocenyl ether ( Fc-O-Fc ) nor diferrocenyl peroxide ( Fc-OO-Fc ) are known so far. However, the corresponding compounds of sulfur, selenium and tellurium are well characterized (see Sect. 5.8). The dichalcogenides Fc-EE-Fc (E = S, Se, Te) are easily obtained by oxidative dimerisation of either the lithium ferrocenyl chalcogenate, Fc-ELi, or the chalcogenols, Fc-EH, for which they can be used as stable precursors (Sect. 5.3.3) [91, 95]. Reaction of the dichalcogenides Fc-EE-Fc with Fc-Li is a possible route to the monochalcogenides, Fc-E-Fc, but the yields are... 

The synthesis generally involves reaction of either the ferrocenyl chalcogenols and l,l -ferrocenylene dichalcogenols, Fc-EH and fc(EH)2, or (preferably) the corresponding lithium derivatives, Fc-ELi and fc(ELi)2, with halides such as acid chlorides, non-metal chlorides and chloro metal complexes (E = S, Se, Te). 

The tellurides, Fc-Te-Fc and Fc-TeTe-Fc, where only obtained in 1987 via the solvated lithium ferrocenyl tellurolate, Fc-TeLi(thf) [102]. Oxidation by air produces Te2Fc2 which, in turn, may be cleaved by Fc-Li to give eventually TeFc2. 

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