Organometallics Metallacycles

However, it is clear that B(C6F5)3 can behave as an electron acceptor, as evidenced by the oxidation of the metallacyclic organometallic derivatives shown in Scheme 27. Norton et al. have observed about 1-2% production of the radical cation of... 

Reactions other than Lewis acid-base associations/dissociations are frequently observed wit donor molecules, leading notably to solvolysis, oxygen or sulfur abstraction, insertion reaction and carbon-carbon coupling reactions. The tendency to form metal-element multiple bonds i remarkable in this respect the activation of dinitrogen by tantalum or niobium is unique. Th formation and chemistry of constrained reactive metallacycles open another promisin fast-developing area, on the frontier with organometallic chemistry. 

Comprehensive coverage has not been attempted, but rather the intention has been to provide an introduction for the non-specialist which illustrates the scope of the field and highlights the main features of interest to organic chemists. Citation of all relevant publications is impracticable because of the large volume of literature. However, it is hoped that those key papers and specialist review articles which are included will enable the reader to locate related literature of interest. Advances in the chemistry of metallacycles and metal-hydrocarbon ir-complexes are thoroughly reviewed in surveys of organometallic chemistry published annually since 1972 (B-72MI12200). 

The synthesis of four-membered ring metallacycles was initially driven by the recognition that low-valent transition metals could mediate cyclopropane carbon-carbon bond cleavage and by the extensive attention devoted to reactivity patterns thought to be relevant to olefin metathesis. More recently, however, organometallic and organic researchers... 

Metallacycle chemistry J. P Collman, L. S. Hegedus, J. R. Norton and R. G. Finke, Organometallic Chemistry of Transition Metals Principles and Use, University Science Book, Mill Valley, Calfornia, 1989, Chapter 10. 

Recent advances in ROMP chemistry have resulted from the finding that the isolated organometallic carbene and metallacycle complexes give living polymers. These systems continue to add monomers to... 

As in the chemistry of the C-H bond, an important problem in organometallic fluorocarbon chemistry is to discover if further reaction chemistry is possible once a C-F bond is successfully attacked. Kiplinger and coworkers demonstrated [48] that the tungsten(II) metallacycles obtained from C-F activation can be... 

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