Cyclopentadienyl and Related Derivatives

4 Cyclopentadienyl and related derivatives. Alkali-metal cyclopentadienyl compounds have been featured in a highlight article in Angew.Chem. NMR spectra and oxidation potentials have been reported for Bu -substituted cyclopentadienyl-metal species. A crystal structure determination of [Ph4P][Cp2Li], obtained from Ph4PCl and CpLi in THF, revealed that the anions 

1 Introduction. - This section of the review is sub-divided into three parts, each of which considers a different coinage metal. As for Section 1 it is dominated by compounds that contain at least one carbon-metal interaction. Synthetic and mechanistic studies are reported first in each part. Thereafter, solid-state, solution and theoretical investigations are presented, in that order. 

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Table 4. Chemical Shifts of Some Carbonyl, Nitrosyl, Cyclopentadienyl, and Related Derivatives of Cobalt...

NMR spectroscopy is a useful new tool to investigate kinetic problems. Attention has been focused on cyclopentadienyl and related complexes, and in a number of cases thermodynamic parameters have been derived in spite of experimental difficulties. First, in a typical experiment, on increasing the temperature, two or more sharp signals broaden, vanish into the noise, then a broad singlet appears and sharpens. Thus from line shape analysis it is possible to determine rates of exchange near the slow and fast exchange limits, but not in the tem-... 

Following the synthesis of tris(cyclopentadienyl) lanthanide complexes, the first examples of organolanthanide derivatives, a vast number of organolanthanide it-complexes with cyclopen-tadienyl (Cp), indenyl (Ind), cyclooctatetraenyl (COT), and related substituted derivatives have been prepared and extensively reviewed [3]. Here we will briefly discuss cyclopentadienyl and allyl derivatives as representatives of organolanthanide K-complexes. 

RUTHENOCENYL DERIVATIVES AND OTHER COMPLEXES OF r/ -CYCLOPENTADIENYL AND RELATED LIGANDS... 

Most organometallic derivatives of Ln and An contain at least one ligand of the 3t-donor/ i-acceptor type, chiefly cyclopentadienyl and related species (including cyclooctatetraenes). While these ligands represent a sort of protective sheath around the metal center, the other ligands present (halides, hydrides, alkyls, etc.) are the reactive centers in organometallic stoichiometric and catalytic reactions. Thus, we will discuss... 

Simple cyclobutanes do not readily undergo such reactions, but cyclobutenes do. Ben-zocyclobutene derivatives tend to open to give extremely reactive dienes, namely ortho-c]uin(xlimethanes (examples of syntheses see on p. 280, 281, and 297). Benzocyclobutenes and related compounds are obtained by high-temperature elimination reactions of bicyclic benzene derivatives such as 3-isochromanone (C.W. Spangler, 1973, 1976, 1977), or more conveniently in the laboratory, by Diels-Alder reactions (R.P. Thummel, 1974) or by cycliza-tions of silylated acetylenes with 1,5-hexadiynes in the presence of (cyclopentadienyl)dicarbo-nylcobalt (W.G, Aalbersberg, 1975 R.P. Thummel, 1980). 

Cyclopentadienyl groups can be incorporated in a manner similar to that shown in eqnation(4) for phosphines. Metallocene derivatives (see Metallocene Complexes),mtani, can be incorporated into these modified polymers. Also, chiral phosphines such as DIOP and BINAP have been immobilized on polymers to be used in asyimnetric hydrogenation catalysis and related reactions. ... 

P. L. Pauson Compounds derived from cyclopentadiene, pp. 107-140a (197) an account of metal cyclopentadienyls, and the organic chemistry of ferrocene. A50. G. A. Olah, ed., Friedel-Crafts and Related Reactions. Wiley (Interscience), New York, 1965. 

Ferrocene, Fe(Ti5-C5H5)2, and related cyclopentadienyl complexes of transition metals in fact are far more thermally stable, less reactive substances than ionic cyclopentadienides, and have an extensive derivative chemistry that is typically aromatic in that their C-H bonds can undergo such electrophilic substitution reactions as Friedel-Crafts alkylation or acylation, nitration, and so on. Moreover, as a substituent, the ferrocenyl group (ri -f sl l5)Fc(ri -( 5l I4) (=R) is even more effective than a phenyl substituent in stabilizing carbenium ions [RCH2]+. The redox and photochemical properties of many metaUocenyl residues make them versatile substituents with many chemical and materials applications. ... 

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