Pentatetraenylidene complexes reactivity

In contrast, the chemistry of higher metaUacumulenylidene complexes containing longer odd carbon chains has been comparatively less studied due to the synthetic difficulties in preparing such species. This fact relies on the increased reactivity of the unsaturated carbon chains towards electrophilic and nucleophilic attacks. In fact, only a limited number of stable pentatetraenylidene complexes have been described, while others have been proposed as highly reactive transient intermediates. 

Experimental information on the reactivity of pentatetraenylidene complexes is still rather rare. The isolated pentatetraenylidene complexes [Cl (dppe)2Ru=C=C=C=C=CPh2]+ (20) [7] and [(CO)5M=C=C=C=C=C(NMe2)2] (M = Cr, W) (22) [8] tvere found to read with secondary amines by addition of the amine across the C3=C4 bond, very likely via an initial nucleophilic attack at C3, to give alkenyl(amino)allenylidene complexes (Scheme 3.32). Analogously, methanol... 

The reactivity of heptahexaenylidene complexes is reminiscent of that of the corresponding pentacarbonyl pentatetraenylidene complexes. Like 23, complex 26... 

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