Other Organometallics

There are a wide variety of methods for introduction of substituents at C3. Since this is the preferred site for electrophilic substitution, direct alkylation and acylation procedures are often effective. Even mild electrophiles such as alkenes with EW substituents can react at the 3-position of the indole ring. Techniques for preparation of 3-lithioindoles, usually by halogen-metal exchange, have been developed and this provides access not only to the lithium reagents but also to other organometallic reagents derived from them. The 3-position is also reactive toward electrophilic mercuration. 

The bimetallic mechanism is illustrated in Fig. 7.13b the bimetallic active center is the distinguishing feature of this mechanism. The precise distribution of halides and alkyls is not spelled out because of the exchanges described by reaction (7.Q). An alkyl bridge is assumed based on observations of other organometallic compounds. The pi coordination of the olefin with the titanium is followed by insertion of the monomer into the bridge to propagate the reaction. 

Although inhibitors are deliberately added to the silicone formulation to control cure rate, unwanted cure inhibition can be caused by other species that react to form strong complexes with the platinum catalyst. Most notable of these undesired inhibitors include organotin and other organometallic compounds, sulfur, polysulfides, polysulfones or other sulfur-containing materials, amines, urethanes or amine-containing materials, unsaturated hydrocarbons in plasticizers, and some solder flux residues. 

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

Reaction with halides or alkoxides of elements less electropositive than A1 affords a useful route to other organometallics ... 

With rare exceptions, such as [Fe(bipy)3]°, oxidation states lower than +2 are represented only by carbonyls, phosphines, and their derivatives. These will be considered together with other organometallic compounds in Section 25.3.6. 

Preparation of the appropriate optically active sulfmate ester is initially required for reaction with a Grignard or other organometallic reagent. If the method is to produce homochiral sulfoxides, the precursor sulfmate ester must be optically pure. An exception to this statement occurs if the reaction yields a partially racemic sulfoxide which can be recrystallized to complete optical purity. 

The reaction has also been performed with other organometallic compounds, for... 

Other organometallic compounds that are hydrolyzed by water are those of sodium, potassium, lithium, zinc, and so on, the ones high in the electromotive series. Enantioselective protonation of lithium enolates and cyclopropyllithium compounds have been reported. When the metal is less active, stronger acids are required. For example, R2Zn compounds react explosively with water, R2Cd slowly, and R2Hg not at all, though the latter can be cleaved with concentrated HCl. How-... 

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... 

Grignard reagents and other organometallic compounds " react with sulfuryl... 

Other organometallic compounds add to isocyanates. Vinyltin reagents lead to conjugated amides. ... 

Activation energies of thermal reactions in organometallic compounds have unfortunately not yet been measured. It would seem that the Group VI carbonyls would offer the best possibilities for such measurements, since their reactions are not complicated by competitive reactions. Unfortunately it cannot be said with confidence that these compounds are representative of aU other organometallic compounds as well. 

The R-Hg bond is chemically stable and is not split by water or weak acids or bases. This is a reflection of the low affinity of Hg for oxygen. It can, however, be readily broken biochemically. Organomercury, like other organometallic compounds, has a strong affinity for SH-groups of proteins and peptides. 

The alkynyl-metal (metal-acetyhde) complex is one of the best building blocks for organometallic dendrimers, since it has some advantages compared to other organometallic complexes [18]. Most of the metal-acetylide complexes are thermally robust and stable, even when exposed to air and moisture. Metal-acetylide complexes are fairly accessible in high yields by well-established synthetic methodology [19]. These features are essential to the construction of dendrimers. 

See other MERCURY compounds See other organometallic nitrates... 

Aluminium Alkyls and other Organometallics, 5, New York, Ethyl Corp., 1967... 

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