Magnesium complexes pyridine oxide

Amines such as diethylamine, morpholine, pyridine, and /V, /V, /V, /V -tetramethylethylene-diamine are used to solubilize the metal salt and increase the pH of the reaction system so as to lower the oxidation potential of the phenol reactant. The polymerization does not proceed if one uses an amine that forms an insoluble metal complex. Some copper-amine catalysts are inactivated by hydrolysis via the water formed as a by-product of polymerization. The presence of a desiccant such as anhydrous magnesium sulfate or 4-A molecular sieve in the reaction mixture prevents this inactivation. Polymerization is terminated by sweeping the reaction system with nitrogen and the catalyst is inactivated and removed by using an aqueous chelating agent. 

The prerequisite for the toxic effect of heavy metals is penetration of the cell wall. For this, certain carriers are needed to transport the heavy metals through lipophilic centres in the cell membrane. Oxines, 2-mercapto-pyridine-N-oxides (III. 11) and dialkyl-dithiocarbamates (III.9) are examples of compounds capable of complexing heavy metal ions such as Cu ions and transporting them into the microbe cell. The carriers named are also toxic, as such, to micro-organisms. But, as a copper carrier, copper-8-hydroxyquinoline is about 100 times more effective than 8-hydroxyquinoline (oxine III. 11.4). Once heavy metal ions have overcome the cell wall with the aid of the carrier molecules, they may compete with magnesium, calcium and potassium ions for receptor sites, inhibit enzymes and cause non-specific precipitation of proteins. 

In analogy to aromatic C-H bonds, alkenyl C-H bonds can also be activated by iron(III) salts in coupling reactions with magnesium or zinc organyls (Scheme 4-250). The reaction requires a pyridine or an imine moiety in proximity to the double bond that supports the C-H bond activation step by chelation of the intermediate iron complex. Tris(acetylacetonato)iron is employed in catalytic amounts and l-bromo-2-chIoroethane or l,2-dichloro-2-methylpropane functions as oxidant. In addition, in most cases a diamine base is added. The reaction results in the stereospecific substitution of the olefinic C-H bond syn to the coordinating group. ... 

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