Main group organometallics reaction with

Reactions of Main Group Organometallic Reagents with Cyclophosphazenes. 67... 

Reaction of main-group organometallic compounds with a metallic oxidant is considered to proceed via transmetaUation. Another reaction path lies in the redox interaction between them, affording the radical species (Scheme 2.57). These reactions are considered to provide a new route to reactive intermediates in oxidative transformations. 

Scheme 2.57 Plausible paths in the reaction of main-group organometallic compounds with a metaUic oxidant...

Another important reaction via transmetallation is carbon-metal bond formation by reaction with bimetallic reagents. This is a useful synthetic method for various main group organometallic reagents. 

Main group organometallic polymerization catalysts, particularly of groups 1 and 2, generally operate via anionic mechanisms, but the similarities with truly coordinative initiators justify their inclusion here. Both anionic and coordinative polymerization mechanisms are believed to involve enolate active sites, (Scheme 6), with the propagation step akin to a 1,4-Michael addition reaction. 

Most main group organometallic compounds undergo nucleophilic reactions with carbonyl groups, whereas 1,4-conjugate addition to enones... 

The majority of main group organometallic compounds for which SET mechanisms were postulated involves Grignard reagents [13,69-75] in their reactions with carbonyl compounds. Even the formation of these important laboratory reagents RMgHal (which does not fall within the scope of this article) is now believed to involve electron transfer mechanisms and radical formation at the surface of metallic Mg [76,77]. In contrast to Grignard compounds with their... 

Chelate coordination-assisted SET reactivity as described in Eq. (12) may be invoked in some remarkable insertion reactions of alkylaluminium porphyrins [139] and are not restricted to the main group organometallics. Photoreactions of low-spin d systems with a filled fag sub-shell such as Co(III) [140] or Pt(IV) [141] with chelating 7r-acceptor ligands also involve CT absorptions and apparent radical pair formation (spin-trapping, CIDNP [141]) before typical followup reactions such as C-alkylation [38,95,140] occur. 

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