Anion fragments centred

In examples 2.22 a and b the metals increase their valence by two, and this is not just a formalism as indeed the titanium(II) and the nickel(O) are very electron rich metal centres. During the reaction a flow of electrons takes place from the metal to the organic fragments, which end up as anions. In these two reactions the metal provides two electrons for the process as in oxidative addition reactions. The difference between cycloaddition and oxidative addition is that during oxidative addition a bond in the adding molecule is being broken, whereas in cycloaddition reactions fragments are combined. 

Glycine anion (230) is decarboxylated when exposed to hydroxyl radicals. The major initial product is an amino radical cation (231), which suffers rapid 100 ns) fragmentation into CO2 and a carbon-centred radical (232). Oxidative decarboxylation... 

In the anion of 17 two Cp Mo03 moieties are bound via an oxygen atom to a (o-tolyl)2Bi+-fragment forming a 10 electron four-coordinate bismuth centre. As anticipated coordination of the second Cp MoOs unit saturates the Lewis acidity of the Bi centre thereby avoiding the formation of a polymeric structure as in 16. Even though 17 is a monomeric complex the... 

It is also shown that it is possible to perform deprotonation reactions on the tungstacyclopentane and form an anionic species 51, in which the unsaturated metallacyclic fragment forms a double bond with the tungsten centre.49... 

Acylation of the monomer activates the latter towards the nucleophilic attack by a lactam anion. Hence, it is rational to use the term activator for lactam derivatives capable of growing (e.g., A-acyllactams) or such compounds which produce the latter much faster than the initiator alone (e.g., acid chloride). In most cases, the activator or its fragments become part of the polymer molecule. Anionic polymerizations in which an activator has been added are designated as activated polymerizations, whereas in non-activated polymerizations the growth centres are produced by the initiator, reaction (23). 

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