Cobalt Compounds Acylcobaltate complexes

Tricarbonyl(naphthalene)chromium, 19 Trimethylsilyl chlorochromate, 327 Cobalt Compounds Acylcobaltate complexes, 101 [Bis(salicylidene-y-iminopropyl)methyl-amine]cobalt(II), 41 Cobalt(II) chloride, 249 Cobalt zeolites, 296 Dicarbonylcyclopentadienylcobalt, 96 Di- x-carbonylhexacarbonyldicobalt,... 

Evidence for the insertion of an olefin group between an acyl group and a cobalt atom has been obtained more directly by analyzing the decomposition products of co-unsaturated acylcobalt tetracarbonyls (CHjp=CH(CH2) COCo(CO)4). The products of thermal decomposition of these complexes depend upon the value of n. When n = 0 or 2 the compounds form relatively stable cyclic olefin 7r-complexes which may be isolated as monotriphenylphosphine derivatives (47). The ir-acrylyl-cobalt tricarbonyl (n o) gives an amorphous polymer on heating (37), whereas the... 

Cobalt complexes derived from Schiff bases 388 catalyzed the hydroxyacylation of electron-deficient alkenes (Fig. 90) [431, 432]. Thus, methyl acrylate 387 reacted with aliphatic aldehydes 386 in the presence of 5 mol% of the in situ generated catalyst, molecular oxygen, and acetic anhydride to 2-acyloxy-4-oxoesters 389 in 56-77% yield. When acetic anhydride was omitted, the yields of products were lower and mixtures of the free hydroxy compounds and acylated compounds resulting from Tishchenko reactions were obtained. Electron-rich alkenes did not undergo the transformation, since the addition of the acyl radical is much slower. The acylcobalt species inserts oxygen instead and acts as an epoxidation catalyst. 

Acylmetal complexes generally react with conjugated dienes to produce useful organic compounds. For example, acylcobalt carbonyls add to butadiene, producing 1 -acylmethyl-7r-allylcobalt derivatives, which then undergo elimination of the elements of HCo(CO)3 on treatment with base to give 1-acyl-diene u6). This reaction can be made catalytic with respect to the cobalt catalyst under proper reaction conditions. 

Acetylene and monosubstituted acetylenes appear to give some of the 7T-(penteno-4-lactonyl)cobalt tricarbonyl complexes on reaction with alkylcobalt or acylcobalt tetracarbonyls also but other products are formed too. These other products have not been characterized but are thought to be linear, low molecular weight polymers of the acetylene or of the acetylene and carbon monoxide with an acyl group at one end of the polymer chain and a cobalt carbonyl group at the other. The formation of cyclic products from the more-substituted compounds and cyclic and linear ones from the less-substituted compounds is explainable because substitution is known to improve many cyclization reactions. 

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