Transition cyclooctatrienes

Cyclooctatetraene was reduced electrochemically to cyclooctatetraenyl dianion. In DMF the product is mostly (92%) 1,3,5-cyclooctatriene at —1.2 V. If the potential is lowered the main product is 1,3,6-cyclooctatriene. Previous experiments, in which the anion radical was found to be disproportionated, were explained on the basis of reactions of the cyclooctatetraene dianion with alkali metal ions to form tightly bound complexes, or with water to form cyclooctatrienes. The first electron transfer to cyclooctatetraene is slow and proceeds via a transition state which resembles planar cyclooctatetraene102. 

Chaudret and coworkers have demonstrated the use of low-valent transition metal olefin complexes as a very clean source for the preparation of nanostruc-tured mono- and bimetallic colloids (Co, Ni, Ru, Pd, Pt, CoPt, CoRh, and RuPt). Syntheses were carried out in the presence of suitable stabilizers using CO or Hj as reducing agents at room or slightly elevated temperature. A number of nanoparticulate metal oxide systems have also been successfully developed by this method. " Olefin complexes are similar to metal carbonyl complex, except the metal is in either low or zero oxidation state. The most commonly used ligands are 1,5-cyclooctadiene (COD), 1,3,5-cyclooctatriene (COT), dibenzylidene acetone (DBA), and cyclooctenyl (CgHjj). 

Figure 3 Transition structure for the electrocyclic ring closure of 1,3,5,7-octatetraene to 1,3,5-cyclooctatriene...

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