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The Decomposition of Transition Metal Alkyls Revisited: Surprising Wellspring of Novel Reagents for Organic Synthesis
Author(s) -
Eisch John J.,
Adeosun Adetenu A.,
Dutta Somnath,
Fregene Paul O.
Publication year - 2005
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200500088
Subject(s) - chemistry , homolysis , reductive elimination , hydride , metathesis , nucleophile , carbene , romp , bond cleavage , photochemistry , reagent , redistribution (election) , transition metal , organic synthesis , metal , medicinal chemistry , catalysis , polymer chemistry , organic chemistry , polymerization , radical , polymer , politics , political science , law
A broad survey of both the simple and double decomposition modes of transition metal alkyls has been undertaken. From the two main processes of C–M bond rupture, homolysis, and β‐metal hydride elimination, the following modes of decomposition and types of useful reagents generated can be distinguished: 1) reductive decomposition of R n ME m – n to yield subvalent, carbene‐ or free‐radical‐like ME m – n , which can cleave π‐ or σ‐bonds by direct epimetallation; 2) β‐metal hydride elimination to produce hydrometallating agents; 3) combined reductive and β‐metal hydride eliminations to produce anionic, and hence more nucleophilic, epimetallating agents; 4) α‐metal hydride elimination thought to be involved in the transition state leading to C–C bond coupling from (RR'HC) 2 ME 2 derivatives; 5) α,μ‐elimination from lithiated RHC(Li)–ME n –1 , which produces alkylidenes, RHC=ME n –2 , capable of ROMP catalysis; 6) metal–hydrogen metathesis, whereby sufficiently acidic C–H bonds become C–M bonds; 7) metal–metal metathesis, whereby RR'ME 2 undergoes an equilibrating redistribution reaction to form R 2 ME 2 and R' 2 ME 2 ; 8) transfer epimetallation, in which epimetallation (point 1) is achieved with R 2 ME 2 in one step by transfer of ME 2 to the substrate with the concomitant loss of R groups; and 9) transfer epimetallation of olefins by R 2 TiE 2 in hydrocarbons to produce titana( IV )cyclopropanes, which serve as active sites in Ziegler–Natta polymerization. In each situation, the reaction‐mechanistic features are analyzed in terms of existing experimental data and evidence. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)