Organotransition metal complexes

R. Mason The chemical bond in organotransition metal complexes present status of experiment and theory, pp. 31-60 (44). 

Over the last decade, the chemistry of the carbon-carbon triple bond has experienced a vigorous resurgence [1]. Whereas construction of alkyne-con-taining systems had previously been a laborious process, the advent of new synthetic methodology based on organotransition metal complexes has revolutionized the field [2]. Specifically, palladium-catalyzed cross-coupling reactions between alkyne sp-carbon atoms and sp -carbon atoms of arenes and alkenes have allowed for rapid assembly of relatively complex structures [3]. In particular, the preparation of alkyne-rich macrocycles, the subject of this report, has benefited enormously from these recent advances. For the purpose of this review, we Emit the discussion to cychc systems which contain benzene and acetylene moieties only, henceforth referred to as phenylacetylene and phenyldiacetylene macrocycles (PAMs and PDMs, respectively). Not only have a wide... 

Morley and co-workers demonstrated that 4,5-disubstituted 1,2,3-se-lenadiazoles react with sulfur or selenium in the presence of organotransition metal complexes to yield the corresponding heteroleptic 1,2-dithiolene or... 

The purpose of this review is to provide the reader with a scenario of what can be accomplished with nickel complexes. It is useful to do this via a series of broad schemes, hypothetical in some cases, which show the main reaction patterns, without considering mechanistic details. Examples will illustrate the various processes, but extension to other substrates or to different conditions often requires use of alternative ligands or solvents, or a change from a neutral complex to a cationic or anionic species, as indicated above. For references to syntheses with nickel see Baker et al. (10). For criteria for the synthesis of coordination compounds and stability of organotransition metal complexes in general, see references (11. 12). Organometallic literature has been collected periodically by Bruce (13). 

One may also resort here to organotransition metal complexes. For example, benzene rings can be selectively activated to nucleophilic attack by complexation to chromium tricarbonyl (Scheme 12.8) [21]. Similarly, an allylic acetate can also be selectively activated in the presence of a bromide (29 versus 3Q) by addition of a palladium(O) catalyst in THF, which coordinates with the double bond [22] (Scheme 12.9). 

Initiation by some organotransition metal complexes involves addition of a positive metallic site to monomer [Baird, 2000]. For example, the complex formed from cyclopenta-dienyltrimethyltitanium and triperfluorophenyl boron initiates polymerization by the sequence... 

A range of organometallic films (either polysilanes or polygermanes, or organotransition metal complexes doped into organic polymer hosts) have been examined for their bulk NLO response results are listed in Table... 

In large part, the synthesis of Cp H is modeled on the Nazarov cyclization4 developed by Threlkel and Bercaw5, 6 for the synthesis of Cp H. The synthesis of [Cp RhCl2]2 is given as an example of an organotransition metal complex which can be prepared from Cp H. 

Pentamethylcyclopentadiene is a useful aromatic building block for the preparation of other compounds. It can be converted to many salts of its conjugate base with alkali metals or strong bases such as butyl lithium.4 These pentamethylcyclopentadienyl anion salts as well as the diene itself can be transformed into n -pentamethylcyclopentadienyl ligands of organotransition metal complexes by many known methods.4... 

In 1951, ferrocene was synthesized by Pauson [17] and Miller [18]. Soon after this synthesis, two groups led by Wilkinson and Fischer, independently reported that ferrocene has a stable carbon-iron 7r-bond [19]. This was the first example of a true organotransition metal complex containing a carbon-metal bond. Since then, numerous organotransition metal complexes have been prepared. The importance of these complexes as intermediates of many synthetic reactions has been discovered. More importantly, some transition metal complexes were found to behave as precursors of active catalysts. 

Norman, N. C. Organotransition metal complexes incorporating bismuth, Chem. Soc. Rev. 1988,17, 269. 

Recent efforts to explore the synthesis and reactivity of organotransition metal complexes with the cyclopentadienyl bisphosphine ruthenium auxiliary have emphasized the potential of this system for the development of new organic synthetic methods, but they have also uncovered a number of stumbling blocks which must be overcome to achieve real success in this area. Future developments in the chemistry of these ruthenium complexes will be based on the successful application of the reactivity trends uncovered in the past work. The rapid expansion of studies in this field since the mid-1980s has made it increasingly difficult for the synthetic chemist to... 

In 1994, Richmond et al.m published an extensive review describing the activation of C—F bonds using organotransition-metal complexes. This review includes a full discussion of C—F bond cleavage reactions of the type shown in Eq. (2). 92... 

Bergman RG. Activation of alkanes with organotransition metal complexes. Science 1984 223 902-908. 

R. G. Bergman, Activation of Carbon-Hydrogen Bonds in Alkanes and Other Organic Molecules Using Organotransition Metal Complexes, Adv. Chem. Ser. 230, 211-20... 

Several excellent reviews are available on the reactivity of organotransition metal complexes of thiophenes <20010M1259, 2000CCR63, 1998ACR109>. In addition, Sadimenko has provided a compendium of all the known syntheses and reactions of the organometallic derivatives of thiophene and benzo[ ] thiophene <2001AHC(78)1>. 

Organometallic complexes are used as precursors for thin films generated by chemical vapor deposition techniques. Supported organotransition metal complexes can serve as both models for film growth and as precursors to films and other materials. 

Supported organotransition metal complexes have important applications in the design and modeling of new catalysts. They are of interest in the modification of surface properties of solids, including electrodes, and as stoichiometric reagents. 

A wide variety of polymeric materials have been used for the immobilization of organotransition metal complexes, including ion-exchange resins and linear and crosslinked polystyrene, polyethylene, and many other polymers. 

---