The M —cp Bond Rupture

Reactions in which the -h 2 oxidation state is retained may also occur Nicp2 + py— [Ni(py)4]2+ 

Nickelocene undergoes reductive substitution with tetracyclene to furnish bis(tetracyclene)nickel(0), y -l,2,3,4-tetraphenyl-5-ketocyclopentenylcyclopentadienyl-nickel, and ra 5-2,3,4,5-tetraphenyl-2-cyclopenten-1 -one  

Similarly, reductive substitution of a cyclopentadienyl ring of cobaltocene by diene, quinone, and cyclopentadienone moieties serves as a synthetic procedure for a series of ( / -ligand)(cyclopentadienyl)cobalt compounds  

Nickelocene reacts with acetylenes to give dinuclear complexes. On the other hand, the reaction of nickelocene with PhCH2MgCl [see equation (9.140)] affords the tri-nuclear cluster, which is isoelectronic with the Co2ip3-CR) CO)g carbonyl  

Metallocenes of the iron triad and some other cuclopentadienyl complexes undergo metallation reactions of the ring and therefore show aromatic properties as in the acylation reactions. Both metallation and acylation occur more easily than in the case of benzene. 

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