Survey of the Cationic Metal Carbonyls and Their Properties by Groups

SURVEY OF THE CATIONIC METAL CARBONYLS AND THEIR PROPERTIES BY GROUPS 

There is a patent claim for the preparation of [C6H6Ti(CO)4]+Br and [C6H6Ti(CO)3(NO)]+Br 47). Apart from this, there appear to be no examples of Group IV metal cationic carbonyls. 

The known vanadium carbonyl cations are of two types, namely a tetracarbonyl, [AreneV(CO)4]+, and a dicarbonyl, [Cp2V(CO)2]+. The tetracarbonyl derivatives are readily prepared under mild conditions by the reaction of an arene with vanadium hexacarbonyl. The arenes used include benzene, its methyl derivatives 28, 29), naphthalene, and anisole 29). The cation is probably formed by oxidation of the intermediary arene vanadium tricarbonyl. 

The red cations are isolated with bulky anions such as fluorophosphate or phenylborate (28, 29). 

An alternative preparation is reported in the patent literature, in which benzenevanadium tetracarbonvl is oxidized in acid media to [C6H6V(CO)4]+ (47). 

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