Cyclopentadienides, sodium complexes

When CpFe(CO)2Br is treated with sodium cyclopentadienide, a complex is formed in which two cyclopentadienyl groups are present ... 

Nickel plays a role in the Reppe polymeriza tion of acetylene where nickel salts act as catalysts to form cyclooctatetraene (62) the reduction of nickel haUdes by sodium cyclopentadienide to form nickelocene [1271 -28-9] (63) the synthesis of cyclododecatrienenickel [39330-67-1] (64) and formation from elemental nickel powder and other reagents of nickel(0) complexes that serve as catalysts for oligomerization and hydrocyanation reactions (65). 

TC-Cyclopentadienyl Nickel Complexes. Nickel bromide dimethoxyethane [29823-39-9] forms bis(cydopentadienyl)nickel [1271 -28-9] upon reaction with sodium cyclopentadienide (63). This complex, known as nickelocene, 7T-(C3H3)2Ni, is an emerald-green crystalline sandwich compound, mp 173°C, density 1.47 g/cm. It is paramagnetic and slowly oxidi2es in air. A number of derivatives of nickelocene are known, eg, methylnickelocene [1292-95-4], which is green and has mp 37°C, and bis( 7t-indenyl)nickel [52409-46-8], which is red, mp 150°C (87,88). 

Verdet and Stille1 employed brominated poly(phenylene oxide) intermediates in an effort to synthesize more stable catalyst supports containing (cyclopentadienyl)metal complexes. Treatment of poly(oxy-2,6-dimethyl-l,4-phenylene) with N-bromosuccinimide under photolytic conditions produced only the bromomethyl derivative if the D.F. did not exceed 0.35. Subsequent treatment of the bromomethylated polymer with sodium cyclopentadienide afforded the cyclopentadienyl functionalized polymer, 5, but the reaction was accompanied by crosslinking and it was not possible to remove the bromomethyl substituents quantitatively. 

Allylic alkylationThis Pd(0) complex, in combination with a small quantity of bis(diphenylphosphino)ethane, is more effective than PdIPfQ.HOjL for alkylation of allylic acetates with the anion of dimethyl malonate. It also permits use of sodium cyclopentadienide as a nucleophile. 

With a Grignard reagent, 1-methylquinolinium ions give products of type (284). A notable reaction of this class is that between the pyridine-sulfur trioxide complex and sodium cyclopentadienide (286)... 

Thallium cyclopentadienide is often used when the reducing power of the sodium salt is too great. The limited solubility of the thallium complex in organic solvents and its toxicity are its chief disadvantages. 

A notable reaction is that between the pyridinesulfur trioxide complex and sodium cyclopentadienide 298 which forms azulene 299 by a sequence involving opening of the pyridinium ring and subsequent closure to the seven-membered carbocyclic ring. 

Tetrakis-cyclopentadienyl cerium (CeCp4) has been reported to be formed by the reaction of bis(pyridinium) hexachlorocerate with sodium cyclopentadienide [17]. Similarly indenyl and fluorenyl derivatives were prepared. Later work showed the same reactants in tetrahydrofurane to yield, Ce(Cp3), tricyclopentadienyl cerium complex instead of Ce(Cp4) [18]. 

LnCp3 complexes, where Ln = Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Er, and Yb have been synthesized by the reaction of anhydrous metal chloride with sodium cyclopentadienide in tetrahydrofuran at room temperature [1],... 

Other routes involve treatment of a metal-trifluorophosphine halide with either sodium or lithium cyclopentadienide (method D), or direct reaction between a metal-PF3 complex and cyclopentadiene (method E). 

Cyclopentadienyl complexes, as previously discussed, are exceptionally numerous and have been the subject of extensive study. Several routes are available for introducing this ligand into a metal complex. One approach is to react a metal compound with the cyclopentadienide ion, C5H5. This ion can be purchased as the sodium salt in solution it can also be prepared by the following two-step process. 

The complexes 3 and 5 were transformed into the mixed sandwich complexes 6 by reaction with thallium cyclopentadienide in benzene and with sodium cyclopentadienide in ethanol, respectively. The structure was determined by X-ray crystallography. ... 

Whereas sodium indenide displays a stereoselectivity similar to phenylzinc chloride (see Table 26), sodium cyclopentadienide and 3-trimethylsilylindene act like soft carbanions. Both substrates 10 and 12 undergo allylic substitution with net retention of configuration to 1127 and 1328, respectively, via attack on the ally ligands of the intermediate 7t-allylpalladium complexes anti to the metal. Again, the ratio of the two possible diastereomers of structure 13 is unknown. 

A general method for the preparation of all / e ta/za/Uocyclopentadienyl compounds is the reaction of sodium cyclopentadienide with a metal halide or complex halide in tetrahydrofuran, ethylene glycol dimethyl ether, di-methylformamide or similar solvent. A solution of the sodium salt is obtained by treating dispersed sodium with the hydrocarbon in tetrahydrofuran ... 

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