Sodium cyclopentadienyl

Indeed, fenocene was first prepared by adding iron(II) chloride to cyclopentadienyl-sodium. Instead of the expected bonded species shown in the equation, fenocene was fonned. 

Describe the similarities and differences in geometries, charge distributions and electrostatic potential maps for cyclopentadienyl sodium, cyclopentadiene and cyclopentadienyl anion. 

Trimethylpyrylium perchlorate is a very versatile and useful starting material. Thus its reaction with cyclopentadienyl-sodium has made 4,6,8-trimethylazulene 12 easily available for general studies of the properties of azulenes 18 and for the synthesis of related compounds.14 In addition, pyrylium salts are readily converted to a variety of pyridine derivatives 9 15 as well as to derivatives of nitrobenzene16 and phenol.9 17,18 It is clear that its value as a starting material is such that it is receiving wide use. 

Reaction with cyclopentadienyl sodium yields bis(cyclopentadienyl) tantalum... 

Treatment of the complex (XXVII X = Cl) with acetylacetone (acacH) in alkali gives the mononuclear a-acetylacetonyl compound [Rh(acac)(C8Hi2)]. The stable, diamagnetic complex cyclo-octa-l,5-dicne-cyclopentadienylrhodium(I), [Rh(C6H6) (CgH )], is formed from the dimer (XXVII X = Cl) and cyclopentadienyl sodium (44, 45). The analogous complex, with cyclopentadiene as the chelating diene, has been prepared in 1-2% yield (91) by the reaction ... 

NaCrO,C H,-2 C4H, 02, Chromatefl -), tricarbonyl(Tp -cyclopentadienyl)-sodium compd. with 1,2-dimethoxyethane-(1 2), 26 343... 

F,SCH, Methanesulfonic acid, trifluoro-iridium, manganese and rhenium complexes, 26 114, 115, 120 platinum complex, 26 126 OiFeCgH, Iron, acetyl dicarbonyl (if -cyclopentadienyl)-, 26 239 0,FeN2C2 Hll(, Iron, tricarbonylbis(2-isocy-ano-l,3-dimethylbenzene)-, 26 54 0.iMoNaCHH5-2 C4H ,02, Molybdate 1 -), tricarbonyl(T) -cyclopentadienyl)-sodium, compd. with 1,2-dimethoxy-ethane-(l 2), 26 343 0,NaWC H5-2 C4H ,02, Tungstate(l -), tricarbonyl(ris-cyclopentadienyl)-... 

Pentamethylcyclopentadienyl) ( j5-cyclopentadienyl) iron has been prepared by the alkylation of ferrocene under Friedel-Crafts conditions with methylchloride,1 and also by reaction of ferrous chloride or FeBr2 DME (DME = 1,2-dimethoxyethane) with equimolar quantities of pentamethyl-cyclopentadienyl sodium and cyclopentadienyl lithium.2,3... 

Care must be taken during this transfer to minimize exposure of the cyclopentadienyl sodium to air. Trace amounts of oxygen cause the formation of a dark brown color and brown solid In the solution. 

Reaction of (i7-C5H5)2TiCl2 with cyclopentadienyl sodium affords in low yield the green (7)5-C5H5)2(Tji -C5H5)Ti(III) complex (27) (42). 

In this group, too, the first observations were made by Thiele 192), who found that cuprous and silver ions are precipitated from aqueous ammoniacal solution by cyclopentadiene, but gave no analytical data. Thallium was later found to be precipitated similarly. Copper (I), however, also yields a white crystalline cyclopentadienyl-triethylphosphine complex, C5H5CuP(C2H5)3, which is stable to water 215) this was, in fact, analogous to an earlier method described by van Peski and Melsen. Attempts to make a complex by the Grignard reagent method or by the action of cyclopentadienyl sodium on cuprous halides were unsuccessful. 

The colorless zinc compound, Zn(CisH6)2, which sublimes at 160° under partial decomposition, is obtained in small yield from zinc chloride and cyclopentadienyl sodium in diethyl ether however, the less stable cadmium compound decomposes, with separation of cadmium, under these conditions (55). The mercury compound, Hg(CsH5)2, is produced in 20% yield by the action of the sodium derivative on mercuric chloride in tetrahydrofuran (215). The action of cyclopentadiene on the complex K2(HgI ) in aqueous alkaline solution results in the precipitation of a mixture of CsHsHgl and Hg(CsH6)2, from which the latter compound may be obtained in good yield by extraction with a mixture of tetrahydrofuran and petroleum ether (62). It forms pale yellow crystals which begin to decompose at about 60° and which melt at 83-85°. The compound is readily soluble in most solvents it decomposes slowly even when kept in the dark at room temperature it is insoluble in water and reacts with neither water nor bases. On the other hand, decomposition occurs in dilute hydrochloric acid. It converts ferric chloride to ferrocene quantitatively, and it yields an adduct with maleic anhydride (215). 

Tricyclopentadienyl bismuth, Bi(C6H5)s, which is obtained from cyclopentadienyl sodium and bismuth trichloride in solvents which do not contain reactive hydrogen, exists as an orange modification which at 18° is converted irreversibly into a black form. It is hydrolyzed by water 73). The analogous carmine compound Sb(C5H6)s, which is also hydrolyzed by water, is prepared by a similar method at low temperature (73). 

Dicyclopentadienyl manganese was first obtained by thermal decomposition of the ammine [MnfNHsle] (CbHb)2 (50, 111). Shortly afterward, it was made in good yield by the reaction between manganese bromide and cyclopentadienyl sodium in tetrahydrofuran (214), and it may also be prepared by the interaction of manganese chloride and an ethereal solution of the Grignard reagent, followed by sublimation (60). At ordinary temperatures it forms brown crystals. 

Ruthenium, the homologue of iron in this group, was also shown to form complexes quite early. Ruthenocene, Ru( 5H5)2, is obtained by treatment of the acetylacetonate of tervalent ruthenium with five times the theoretical quantity of the Grignard reagent (206), or, better, by the action of cyclopentadienyl sodium on ruthenium trichloride in tetrahydrofuran (47). It forms pale yellow scales which sublime at 120° and melt at 200°. Its properties are closely similar to those of ferrocene it is soluble in organic solvents, and in the absence of air is not attacked by bases or by sulfuric or hydrochloric acid. Oxidation converts it into the pale yellow [Ru( 5H6)2] + ion. 

Osmocene, Os( sHo)2, has recently been made, in 20% yield, by the interaction of cyclopentadienyl sodium and osmium tetrachloride (47). It forms colorless crystals which melt at 230° again, it dissolves in organic solvents water, however, has no action on it, nor does it dissolve. The hydrogen atoms in the cyclopentadienyl rings, like those in ferrocene and ruthenocene, can undergo substitution this property has not been described for other metal cyclopentadienyl compounds, except in one... 

Chromium forms a cyclopentadienyl compound similar to ferrocene (p. 499). Cyclopentadienyl sodium reacts with anhydrous chromium (I I) chloride in tetrahydrofuran to give red (C5H5)2Cr. By oxidising this, compounds containing the (C5H5)2Cr+ ion are easily obtained (Cotton and Wilkinson, 1954). When cyclopentadiene mixed with molybdenum or tungsten carbonyl is passed through a tube heated to 300 the dicyclopentadienyl hexacarbonyl is formed (Wilkinson, 1954) ... 

MoNaOjCiHj CjHiiiO , Molybdate(l -), tri-carbonyl(Ti -cyclopentadienyl)-, sodium, compd with 1,2-dimethoxy-ethane(l 2), 26 343... 

Cyclopentadienyl-tin(II) and -tin(IV) compounds can be made from cyclopentadienyl sodium, and ethynyltin(IV) compounds have been obtained by treating a mixture of the alkyne and tin halide with a tertiary amine (equation 4-18).23... 

Usually, initiation of chain growth wifh rhodium catalysts does not require an alkylating agent. Kern has postulated fhe formation of an active species via oxidative addition of the terminal alkyne to rhodium, so-called hydroethynylation [138], This reaction has also been reported by Werner et al. [141] when contacting [RhCl(P Pr3)2] with phenylacetylene in fhe presence of pyridine, the alkyne hydride complex 23 is generated (Scheme 7.10). In fhe presence of a base such as cyclopentadienyl sodium, a tetracoordinated Rh complex 24 was obtained and isolated. 

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