Indenyl anion

SRNl substitution include ketone enolates,183 ester enolates,184 amide enolates,185 2,4-pentanedione dianion,186 pentadienyl and indenyl carbanions,187 phenolates,188 diethyl phosphite anion,189 phosphides,190 and thiolates.191 The reactions are frequently initiated by light, which promotes the initiating electron transfer. As for other radical chain processes, the reaction is sensitive to substances that can intercept the propagation intermediates. 

This point is borne out by the structure of tris indenyl samarium (5d). An earlier report of the nmr spectrum was interpreted as evidence of covalent bonding in the tetrahydrofuran adduct of samarium triindenide 66). Indenyl anion. 

Other delocalized anions have been investigated as well, such as complexes of indenyl and fluorenyllithium. These data are also included in Table 8. The sole investigated indenyllithium system was the TMEDA complex. It is known from X-ray crystallography that the lithium cation is located above the five-membered ring and that the TMEDA binds in a bidentate fashion . The x value is somewhat larger than for the corresponding cyclopentadienyllithium complexes (entry 9). 

Topological charge stabilization explains the greater stability of indole (88), benzo[b]furan (89), and benzo[6]thiophene (90) compared to their positional isomers (91)-(93) when the largest 7r-charge densities at the 1,3-positions of the five-membered ring in the 10 7r-electron indenyl anion (94) are taken into account (77JA1692). Such an order of the relative stability is consistent with the RE values (Table X). 

It is noteworthy that the indenyl complex RuCl(ri -C9H7)(PPh3)2l4 provides an efficient catalyst precursor for the anti-Markovnikov hydration of terminal alkynes in aqueous media, especially in micellar solutions with either anionic (sodium dode-cylsulfate (SDS)) or cationic (hexadecyltrimethylammonium bromide (CTAB)) surfactants [38]. This system can be applied to the hydration of propargylic alcohols to selectively produce P-hydroxyaldehydes, whereas RuCl(Cp)(PMe3)2 gives a,P-unsat-urated aldehydes (the Meyer Schuster rearrangement products)(Scheme 10.8) [39]. 

MI1), which can formally be derived from the isoconjugated indenyl anion 1. As they are compounds with an o-quinodimethane structural element 3, they are especially suited for inter- and intramolecular cycloadditions. 

A rigorous theoretical treatment of the non-alternant and heterocyclic indolizine is extremely difficult and, even for the related isoconjugate hydrocarbon, far from conclusive. Many questions, however, in which experimentalists are interested may be answered in a satisfactory way on the basis of a perturbational treatment. This approach has been used for a discussion of the electronic spectra of indolizine and some azaindolizines (63JCS3999). Following first-order PMO theory the 7r-stabilization which follows from aza substitution at the different positions of the model molecule depends on the ir-electron density qt as well as the change in electronegativity Sat (B-75MI30801). The perturbations caused by aza substitution of the indenyl anion are depicted in Scheme 1. 

If a potential electron acceptor is built into the anion itself, electron redistribution within the excited state may represent an pseudointramolecular electron transfer. For example, in the photodehalogenation of halosubstituted diphenyl-indenyl anions, eq. 84 (257),... 

Hydrocarbon anions, such as cyclopentadienyl and analogs (fluorenyl, indenyl, pentadienyl), substitute for fluoride, leading, for example, to phenylcyclopentadiene as a Cr(CO)3 complex on the arene (equation 15).67... 

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 cyclopentadiene anion is stabilized by five equivalent resonance structures. The anion is an aromatic anion by virtue of it being a six-jr-electron system. The indenyl anion is stabilized by a total of seven resonance contributors. However, they are nonequivalent and all but one require that the aromatic cloud of the benzene ring is disrupted. Thus, while the negative charge is well delocalized, the resonance stabilization is less than that of the cyclopentadiene system. Thus the proton is not as easily removed, making indene a weaker acid. 

Electron photodetachment spectra for indenyl and fluorenyl anions have been measured and the electron affinities of the corresponding radical and bond dissociation energies of the corresponding neutrals determined. Comparison has been made with solution-phase data in an attempt to determine the dependence of gas and solution properties on ionic size and extent of charge distribution.3 Benzocyclopropenyl anion... 

This mechanistic consideration is in accord with the result from arylation of indene (7) [5]. The arylation occurs exclusively at the 1,3-positions, those with the highest electron density, of intermediary indenyl anions (9). The related arylation of azulene also proceeds exclusively at 1,3-positions, interpreted as electrophilic aromatic substitution, again by an electrophilic aryl-Pd species [10]. 

Organic fragments which can serve as n ligands include cyclopentadienyl, indenyl, and fluorenyl systems as well as polynuclear aromatic anionic and dianionic species. From IR and NMR data it has been concluded that the bonding in these complexes may be regarded as fully ionic. 

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