Organometallic compounds, also

Most other organometallic compounds also react with oxygen. Aryllithium reagents have been converted to phenols by treatment with oxygen. Trialkylboranes and alkyldichloroboranes (RBCI2) can be conveniently converted to hydroperoxides by... 

Brief descriptions follow of less general but very useful methods of forming organometallic compounds (also see Table 14-7). In each of these preparations the solvent must be inert to all of the organometallic compounds involved. 

The formation of disilane derivatives is not possible only with metals organometallic compounds also react with halosilanes. West et al.509 found formation of disilanes in the reaction with Grignard compounds ... 

The very rich structural chemistry of organometallic compounds also provides many examples of conformational polymorphism. For instance, cyclic ligands often have low barriers to rotation so that conformational variations between polymorphs might not be unexpected. Riley and Davis (1976) reported the structures of the dimorphic sandwich compound 5-VII, a system in which the molecular geometry is determined by the crystallographic site symmetry for both polymorphs (Fig. 5.8). In the triclinic form, the molecular site symmetry is C, requiring the trans orientation... 

Carbanions arising from other organometallic compounds also react with phosphorus with the formation of organophosphorus compounds. Heating tetraphen-yltin with elemental phosphorus (1 2) for 16 h to 320 oC produced triphenyl-phosphine in 85% yield 5) ppoof for the intermediate formation of tin-phos-... 

Organometallic compounds also undergo reactions of coordinated ligands readily. A simple example involves the susceptibility of coordinated carbon monoxide towards nucleophilic attack. The [Mo(CO)6] complex reacts with methyllithium (6.48), with the new ligand produced at one site also able to undergo additional reactions, not described here. 

These differences in reactivity of the various organometallic compounds also appear on their hydrolysis, which affords a hydrocarbon and a metal hydroxide. For instance, alkyl derivatives of alkali or alkaline-earth metals undergo rapid and violent reaction with water, whereas the quite weakly polar alkylsilicons do not react at all under these conditions. 

The spectra of organometallic compounds also provide useful structural information. For example, most protons bonded directly to metals (in hydride complexes. Section 13.4.3) are very strongly shielded, with chemical shifts commonly in the approximate range of -5 to -20 ppm relative to Si(CH3)4. Such protons are typically easy to detect because few other protons commonly appear in this region. 

The enamine 193 as a carbon nucleophile reacts with TT-allylpalladium chloride to give 2-allylcyclohexanone after hydrolysis [84]. Hard carbon nucleophiles of organometallic compounds also react with TT-allylpalladium complexes. A steroidal side chain was introduced to 194 to afford 197 regio- and stereoselectively by the... 

Organometallic compounds also may be formed by the dissolution of a metal cathode during the reduction of unsaturated organic compounds. Tomilov and Kaabak 04,105 have studied the reduction of acrylonitrile, H2C=CHCN, at a tin cathode in aqueous alkaline solution. Electrolysis produced [Sn(CH2CH2CN>4]. Other reactions that take place at sacrificial cathodes have been reviewed. Despite the long history of reactions that involve sacrificial cathodes, current ideas about the mechanisms of these reactions do not explain all aspects of the chemistry involved and have little predictive power. 

The introduction of additional alkyl groups mostly involves the formation of a bond between a carbanion and a carbon attached to a suitable leaving group. S,.,2-reactions prevail, although radical mechanisms are also possible, especially if organometallic compounds are involved. Since many carbanions and radicals are easily oxidized by oxygen, working under inert gas is advised, until it has been shown for each specific reaction that air has no harmful effect on yields. 

Regioselectivity of C—C double bond formation can also be achieved in the reductiv or oxidative elimination of two functional groups from adjacent carbon atoms. Well estab llshed methods in synthesis include the reductive cleavage of cyclic thionocarbonates derivec from glycols (E.J. Corey, 1968 C W. Hartmann, 1972), the reduction of epoxides with Zn/Nal or of dihalides with metals, organometallic compounds, or Nal/acetone (seep.lS6f), and the oxidative decarboxylation of 1,2-dicarboxylic acids (C.A. Grob, 1958 S. Masamune, 1966 R.A. Sheldon, 1972) or their r-butyl peresters (E.N. Cain, 1969). 

Organometallic Compounds. Ruthenium, predominately in the oxidation states 0 and +2, forms numerous mononuclear and polynuclear organometaUic compounds. A few examples of compounds in both higher and lower oxidation states also exist. The chemistry of polynuclear mthenium complexes is extensive and has been reviewed (53—59). 

Organometallic Compounds. The predominant oxidation states of indium in organometalUcs are +1 and +3. Iridium forms mononuclear and polynuclear carbonyl complexes including [IrCl(P(C3H3)3)2(CO)2] [14871-41-1], [Ir2014(00)2] [12703-90-1], [Ir4(CO)22] [18827-81 -1], and the conducting, polymeric [IrCl(CO)3] [32594-40-4]. Isonitnle and carbene complexes are also known. 

This index contains over 40,000 individual entries to the 6200 text pages of Volumes 1-7. The index mainly covers general classes of heterocyclic compound and specific heterocyclic compounds, but also included are natural products, other organic and organometallic compounds where their synthesis or use involves heterocyclic compounds, types of reaction, named reactions, spectroscopic techniques and topics involving heterocyclic compounds. 

Today the term anionic polymerisation is used to embrace a variety of mechanisms initiated by anionic catalysts and it is now common to use it for all polymerisations initiated by organometallic compounds (other than those that also involve transition metal compounds). Anionic polymerisation does not necessarily imply the presence of a free anion on the growing polymer chain. 

Benzyne can also be generated from o-dihaloaromatics. Reaction of lithium amalgam or magnesium results in formation of a transient organometallic compound that decomposes with elimination of lithium halide. l-Bromo-2-fluorobenzene is the usual starting material in this procedure. 

Similar structural diversity has been established for the heavier alkali metals also but it is unnecessary to deal with this in detail. The sUTictural chemistry of the organometallic compounds in particular, and of related complexes, has been well reviewed. 

Organolithium reagents are also valuable in the synthesis of other organometallic compounds via... 

Organometallic compounds of Ga, In and Tl have been less studied than their Al analogues. The trialkyls do not dimerize and there is a general tendency to diminishing thermal stability with increasing atomic weight of, M. There is also... 

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