Organocobalt m complexes with Schiff base ligands

The ease of synthesis of diene-cobalt complexes depends on the position of the cobalt on the dienyl fragment (position 1 or 2) and it also depends on the substituent on the carbon atoms (1—3). Various synthetic routes are shown 

An alternative route using dienyl triflate ligands with a zinc-mediated cobaloxime reduction has also been used for simple cobaloxime-substituted alkenes 177 (Equation (24)).  

Vinylallenes can be hydrometallated to produce 1-cobaloxime-substituted dienyl complexes (Equation (25)). Cobaloxime-substitued 1,3-diene without a substituent in the 3-position will participate in thermal and Lewis acid-catalyzed Diels-Alder reactions, but the resulting cycloadducts apparently rearrange and give products with 

The 2-cobaloxime dienyl complexes substituted in 3-position could not effect Diels-Alder reactions. To circumvent this synthetic limitation, 3-subtituted 1-cobaloximes have been synthesized (Equation (25)). 

The reaction of the 1,1-disubstituted allenic tosylate with cobaloxime anion afforded the S M2-product 187 rather than the S M2 -product (Equations (26) and (27)).  

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