Important organometallic chemistry taking place at the CoCp unit

3 Important organometallic chemistry taking place at the CoCp unit 

It is very well established that 16-electron species such as [CsRsML] (M = Rh, Ir) generated in situ undergo facile oxidative addition of CH bonds of saturated hydrocarbons or arenes (see COMC (1995) and COMC (1982)). This situation is likely to be due to the fact that iridium and rhodium complexes are kinetically far more stable than cobalt. However, during the last decade, some CH activations were found to take place on some typical cobalt complexes. 

Wadcpohl et al. have reported earlier the exceptional CH activating properties of CpCo(C2H4)2, that led to the cleavage of both methylene CH bonds of CpCo( -C5H6) in 344 (Equation (58)).  

More recently, a related reaction was found to take place to afford a heteronuclear bimetallic compound 345 (in poor yields however), when cyclopheptatrienyl derivatives of Cr, Mo, and W were allowed to react with the same electron-rich cobalt complex (Equation (59)).  

The chromium derivative led to a reversible reaction as its treatment with carbon monoxide afforded the starting compounds. 

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