Cyclopentadiene sodium derivative

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). 

Derivation From ferrous chloride and cyclopentadiene sodium. 

This method has the disadvantage that prior preparation of the cyclo-pentadienylmetal tricarbonyl dimers is necessary, either from the metal hexacarbonyl and cyclopentadiene or its dimer 128, 129) or in the cases of certain substituted derivatives from the metal hexacarbonyl and fulvene derivatives 44). Neither of these preparative methods works in the case of the chromium derivative [CsH5Cr(CO)3]2, which must be obtained either from the anion [C5HsCr(CO)3] or from (CsHs)2Cr (see below). This method has the advantage, however, that the solution of the sodium derivative Na[C5HsMo(CO)3] is free from sodium cyclopentadienide, a possible complicating impurity in certain reactions. 

Enol ether additives were used to probe the protonation of 3-cyclopen-tenylidene (127). Treatment of A-nitroso-A-(2-vinylcyclopropyl)urea (124) with sodium methoxide generates 2-vinylcyclopropylidene (126) by way of the labile diazo compound 125 (Scheme 25). For simplicity, products derived directly from 126 (allene, ether, cycloadduct) are not shown in Scheme 25. The Skat-tebpl rearrangement of 126 generates 127 whose protonation leads to the 3-cyclopentenyl cation (128). In the presence of methanol, cyclopentadiene (130) and 3-methoxycyclopentene (132) were obtained.53 With an equimolar mixture of methyl vinyl ether and methanol, cycloaddition of 127 (—> 131)... 

The product was shown to be the THE adduct, but a later modification of the procedure by E. 0. Fischer and H. Fischer (99), using benzene or diethyl ether in place of THE and the potassium salt in place of the sodium salt of cyclopentadiene, produced solvent-free complexes of Tb, Ho, Tm and Lu. The remaining tricyclopentadienides have since been made by various workers using similar methods (53, 100, 101). All of the complexes behave similarly. They are very air- and moisture-sensitive, are stable to heat, and sublime, except for the europium derivative, at elevated temperatures. They are insoluble in cyclohexane, benzene... 

The anion of cyclopentadiene has also been demonstrated to add via ligand addition (inversion).105 385-386 Indenyl nucleophiles derived from the corresponding allylsilane have been classified as adding via ligand addition,385 but the sodium salt of the indenyl anion has curiously been suggested to add via addition directly to the metal.386... 

The preparation of highly functionalized cyclopentadiene derivatives may by achieved by using oxalenes or their pyrylium salts (90 and 92, respectively), (see Scheme 14, where X = O). In this way, azalenes 26,51 29,8Z 88 32,51 or 3651 can be obtained by heating salts (90) with primary amines in dimethyl-formamide (Eq. 6). The reaction with sodium hydrogen sulfide gives thialenes... 

Common to these molecules with their cyclopentadiene moieties is the so-called fulvene subunit 27. The first fulvenes, 6,6-dialkylfulvenes, were prepared as early as 1906 by Thiele et al. from sodium cydopentadienide and ketones [16]. The parent hydrocarbon 27 and many other derivatives have been thoroughly studied since the 1960s [17-19]. Diazocyclo-pentadiene (28), which is also easily prepared from cydopentadienide, is a heteroanalogue of fulvene. It has frequently been used as a precursor to other theoretically interesting molecules containing annelated cydopentadiene moieties, because its irradiation readily generates the cyclopentadienylidene 29. This carbene has, for example, been trapped with alkynes to form spiro-annelated cydopentadiene derivatives 30 (Scheme 5) [20]. It has been proved by UV spectroscopy [21] and supported by calculations [22] that these spiro[2.4]heptatrienes (so-called [1.2]spirenes) 30 experience a spedal kind of electronic... 

Scheme 10. Reaction sequence for the synthesis of tri-, tetra-, and penta(isopropyl)cyclo-pentadienes (34,35) from di(isopropyl)-Cp (59) via a series of metallations/alkylations. Tri(isopropyl)-Cp is obtained in a 4 1 mixture of the 1,2,4- and 1,2,3-substituted isomers. The C—H acidic tetra(isopropyl) isomers are separated from the 5,5 -geminal dialkylated forms by their transformation in the sodium salt and evaporation of the nonmetallated components. Subsequent hydrolysis yields l,2,3,4-tetra(isopropyl)cyclopentadiene in an iso-merically pure form. Similarly, l,2,3,4,5-penta(isopropyl)-Cp is purified after separation of the 1,2,3,S,5 derivative as the main alkylation product. For more details and the respective yields, see Refs. 34 and 35.

Roesky introduced bis(iminophosphorano)methanides to rare earth chemistry with a comprehensive study of trivalent rare earth bis(imino-phosphorano)methanide dichlorides by the synthesis of samarium (51), dysprosium (52), erbium (53), ytterbium (54), lutetium (55), and yttrium (56) derivatives.37 Complexes 51-56 were prepared from the corresponding anhydrous rare earth trichlorides and 7 in THF and 51 and 56 were further derivatised with two equivalents of potassium diphenylamide to produce 57 and 58, respectively.37 Additionally, treatment of 51, 53, and 56 with two equivalents of sodium cyclopentadienyl resulted in the formation of the bis(cyclopentadienly) derivatives 59-61.38 In 51-61 a metal-methanide bond was observed in the solid state, and for 56 this was shown to persist in solution by 13C NMR spectroscopy (8Ch 17.6 ppm, JYc = 3.6 2/py = 89.1 Hz). However, for 61 the NMR data suggested the yttrium-carbon bond was lost in solution. DFT calculations supported the presence of an yttrium-methanide contact in 56 with a calculated shared electron number (SEN) of 0.40 for the yttrium-carbon bond in a monomeric gas phase model of 56 for comparison, the yttrium-nitrogen bond SEN was calculated to be 0.41. 

The dicyclopentadienyl derivatives of these elements which are known at the present time (those of magnesium and calcium) are in many respects similar to those of the alkali metals, being colorless, saltlike compounds. The magnesium compound was successfully prepared by the interaction of sodium cyclopentadienyl and magnesium bromide in tetra-hydrofuran 214), by thermal decomposition of cyclopentadienyl magnesium bromide 214) and, recently, by the action of cyclopentadiene... 

The starting material for preparation of these derivatives, [Ru2(00)4(11 -CsH5)2], has previously been obtained by the reaction of sodium cyclo-pentadienide with a dihaloruthenium(II) carbonyl [Ru(CO)2l2] (ref. 3) or [Ru(CO)3Cl2]2(ref. 4) prepared by carbonylation of the corresponding ruthenium(III) trihalide. A more facile synthesis was later reported, involving the reaction of triruthenium dodecacarbonyl with cyclopentadiene. The procedure described herein represents a modification of this second method, resulting in an improved yield. 

Alternatively, the 5,6-double bond in the initial adduct can be elaborated via Diels-Alder reactions with cyclopentadiene derivatives and this provides an entry to the tetracy-clo[5.2.1.0 0 ]decane series. Hence reaction of the diethyl azodicarboxylate adduct with hexachlorocyclopentadiene gave the adduct 13 which was elaborated to give endo,syn-l,7,8,9,10,10-hexachlorotetracyclo[5.2.1.0 0 ]dec-8-ene (14). Similar syntheses yield derivatives with a variety of substituents at CIO and in this series it was found that sulfuric acid hydrolysis of the carbamates gave a better yield than sodium hydroxide in methanol. The... 

Reaction of the (2-mcthylcnecyclopropyl)phenylsulfonium salt 1 with sodium cyclopentadien-ide in furan for 40 minutes at room temperature and then 14 hours at 0°C gave a Diels-Alder adduct of methylenecyclopropene to cyclopentadiene in 13% yield, apparently derived by elimination of the elements of methyl phenyl sulfide from the salt. " ... 

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