Reaction of [(η 5 -C 5 H 4 Me) 4 Fe 4 (HCCH)-(HCCBr)](PF 6 ) ([2](PF 6 )) with AgPF 6 in acetonitrile gave [(η 5 -C 5 H 4 Me) 4 Fe 4 (HCCH)(HCCNCMe)](PF 6 ) 2 ([3]-(PF 6 ) 2 ). The X-ray diffraction study revealed that the cationic [CCH] subunit is stabilized through coordination of the acetonitrile molecule to the cationic carbon atom. As a synthon for a donor-free [(η 5 -C 5 H 4 Me) 4 Fe 4 (HCCH)(HCC)] 2+ , [(η 5 -C 5 H 4 Me) 4 Fe 4 (HCCH)(HCCL)](PF 6 ) 2 ([6](PF 6 ) 2 , L = pyrazine) was synthesized by the reaction of [2](PF 6 ) with AgPF 6 in the presence of pyrazine. Treatment of [6](PF 6 ) 2 with tertiary amines in acetonitrile led to deprotonation of acetonitrile to form [(η 5 -C 5 H 4 Me) 4 Fe 4 (HCCH)-(HCCCH 2 CN)](PF 6 ) ([11](PF 6 )). Treatment of [6](PF 6 ) 2 with maleimide in the presence of tertiary amine in acetonitrile allowed the functionalization of the coordinated acetonitrile through the nucleophilic attack of maleimide at the nitrile carbon atom.

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