Organometallic complexes cycloaddition reactions

The present volume contains 13 chapters written by experts from 11 countries, and treats topics that were not covered, or that are complementary to topics covered in Volume 1. They include chapters on mass spectra and NMR, two chapters on photochemistry complementing an earlier chapter on synthetic application of the photochemistry of dienes and polyenes. Two chapters deal with intermolecular cyclization and with cycloadditions, and complement a chapter in Volume 1 on intramolecular cyclization, while the chapter on reactions of dienes in water and hydrogen-bonding environments deals partially with cycloaddition in unusual media and complements the earlier chapter on reactions under pressure. The chapters on nucleophiliic and electrophilic additions complements the earlier chapter on radical addition. The chapter on reduction complements the earlier ones on oxidation. Chapters on organometallic complexes, synthetic applications and rearrangement of dienes and polyenes are additional topics discussed. 

Free 1,2,5-triphospha Dewar benzene derivative 95 is formed in two steps from 3 mol of 44a by oxidative decomplexation of the triphosphacyclohexa-l,4-diyl-2,5-diene ligand of the Hf complex 96 <1997CB1491>. An organometallic [2+1+1] cycloaddition reaction between the phosphinidene complex 97, 44a, and a coordinated CO gives access to the 1,2-diphosphacyclobutenone complex 98 (Scheme 31) <1998CEJ1917>. 

Another type of SO2 reaction with organometallics is cycloaddition to 2-alkynyl (propargyl) complexes of Fe, Mn, Mo and An example is the reaction of... 

Organometallic complexes of Ni(0) display a rich array of reactivity both in stoichiometric reactions (e.g. oxidative additions see Oxidative Addition), cycloadditions, etc.)... 

It appears likely that transient metallacyclobutanes are involved in a variety of organic reactions which are catalyzed by transition metal complexes. Thus, cycloadditions of activated alkenes to strained hydrocarbons such as quadricyclane and bicyclo[2.1.0]pentane are catalyzed by complexes such as Ni(CH2=CHCN)2 and probably involve initial formation of a nickelacyclobutane (Scheme 2) (79MI12200). The nature of the organometallic intermediates in related metal-catalyzed rearrangements (72JA7757) and retro-cycloaddition reactions (76JA6057) of cyclopropanoid hydrocarbons, e.g. bicyclo[n.l.O]alkanes, has been discussed. 

Complexes of iron and other metals which are prepared from a allyl or propargyl organometallic compounds and (NC)2C = C(CN)2, SO2, or related unsaturated electrophilic molecules via cycloaddition reactions are important because such complexes may find application in organic synthesis " ... 

R. L. Zuckerman, R. G. Bergman, Mechanistic investigation of cycloreversion/cycloaddition reactions between zirconocene metallacycle complexes and unsaturated organic substrates. Organometallics 20, 2001 1792. 

USE OF ORGANOMETALLIC COMPLEXES IN THE [3+2] CYCLOADDITION REACTION WITH CYCLOPROPANES... 

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