Heavy metal salts, carbonyl complex

Oxidation of alcohols to carbonyl compounds is an important reaction. Stoichiometric oxidants such as chromates, permanganates and MO4 (M = Ru, Os) are the commonly used reagents [19a,59,60]. However, they are going out of favour increasingly because they create heavy metal wastes . In view of this, development of environmentally friendly heterogeneous catalysts for alcohol oxidation is very important. In the use of catalytic amounts of transition metal salts or complexes as homogeneous catalysts for the oxidation of alcohols [61-64], separation of the catalyst from the reaction mixture and its subsequent recovery in active form is cumbersome. Heterogeneous catalysts for this kind of reaction are therefore necessary [65]. Clearly, encapsulation and/or immobilization of known... 

Using a somewhat different approach, Fischer and Fichtel (85) have obtained a variety of ethylene-containing cationic complexes by reaction of TT-cyclopentadienyl carbonyl halides of Mo, W, and Fe with ethylene under pressure in the presence of aluminum chloride. The cations were isolated in the form of their salts with heavy anions such as PFe , B(C6H5)4, etc. Presumably the aluminum chloride serves as a halogen acceptor and activates a coordination site on the metal, facilitating coordination of ethylene. 

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