Use of transition organometallic

The formation of high polymers of olefins in the presence of titanium halogenides with no specially added organometallic co-catalysts was discovered long ago [see (147), and the references therein], A complete description of various alkyl-free polymerization catalysts based on the use of transition metal chlorides may be found in the review by Boor (17), where a comparison of these catalysts with traditional two-component systems is given. 

Carbon-carbon bond formation is the most important reaction in synthetic organic chemistry. Various carbon sources can be utilized for the construction of carbon skeletons. Carbon dioxide (C02) is a nontoxic, cheap, and attractive Ci-source.1,la ld The incorporation of C02 into organic compounds can be achieved by use of various organometallic reagents or catalysts, especially those of transition metals.2 2a 2d This chapter focuses on the carbon-carbon bond formation reactions between C02 and acetylenes and dienes, and covers literature from 1993 to 2004. Subsections are categorized according to metals. 

Phase transfer catalysis has more recently been applied to the important area of organometallic chemistry(18). Reported applications include both the preparation(19) and the use of transition metal catalysts in isomerizations(20), carbonylations(21) and reductions(22). 

The activation of C-H bonds for direct C C bond formation reactions has the potential to become very important especially if it can be accomplished for sp C-H bonds, in methane or alkanes as these are the major feedstocks available. In addition, C-H bond activation of functionalized organic compounds for selective C-C bond formation has been and will continue to be a very important goal of organometallic catalysis. So far the use of transition metal complexes has led to interesting results which however are not yet industrially relevant. 

The efficiency of transmetalation from boron to palladium in the catalytic 1,4-addition of aryl or 1-alkenylboronic acids to enones encouraged us to extend the protocol to the addition of aryl- and 1-alkenylboronic adds to aldehydes in an aqueous solution (Eq. 4). The insertion of carbonyl groups into transition metal-carbon bonds has not received much attention, but the catalytic use of transition metals may allow such addition of various organometallics which are inert without a catalyst, the asymmetric addition using a chiral phosphine complex, or the reaction in an aqueous phase. 

More recently there has been a strong growth of interest in the use of transition metals as homogeneous catalysts in aqueous solution. These processes involve the intermediacy of organometallic compounds for cases where the catalysts are simple transition-metal halide salts or where the metal complexes contain water-soluble tertiary phosphines as ligands 3,4). 

The Journal Of Organometallic Chemistry several times a year pubhshes annual surveys arranged according to metallic element. Eor example, Vol. 404, published in Eebruary 1991, contains annual surveys for 1989 of organic compounds containing Sb, Bi, and Ee, and the use of transition metals in organic synthesis, and surveys for 1988 covering B, Ru, and Os. 

Chapter 12 serves as an introduction to a huge area of chemistry devoted to the use of organometallic compounds for the construction of complex molecules. The material covered in Chapter 12 exemplifies several of the most important applications of organotransition metal chemistry to organic synthesis. Thousands of articles have appeared over the past 10 years that report on either the use of transition metal compounds in key steps of syntheses, which would be difficult or even impossible to carry out without transition metals, or on the development of novel methodology that may have many applications to synthesis down the road. Research on the connection between organometallic chemistry and synthesis remains active and fruitful, and there is every indication that this endeavor will continue to hold the interest of chemists for many years to come. 

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