Hexapentaenylidene Complexes

Until now, hexapentaenylidene complexes are unknown, however, a hexapentaenylidene complex has been proposed as an intermediate in the formation of a Cg-bridged diruthenium complex (Scheme 3.20) [35]. 

Attempts to generate a hexapentaenylidene complex by protonation of ]Cp (NO) (PPh3)Re-C = C-C = C-C = C-C6H4Me-4] have failed. Protonation occurs at C2 to give the corresponding cationic vinylidene complex [36]. 

Scheme 3.20 Postulated hexapentaenylidene complex as intermediate in the synthesis of a Cg-bridged diruthenium complex.

Since hexapentaenylidene complexes have until now neither been isolated nor spectroscopically detected nothing is known about their reactivity. However, a C-nucleophile was suggested to add to C5 of a hexapentaenylidene complex generated in situ by protonation of a triynyl mthenium complex (see Scheme 3.20) [35]. 

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