Abstract The reaction between CH3Cs5H4Mn(CO)3 and LiN(C2H5)2 and subsequent alkylation with [(C2H5)3O]BF4 affords CH3C5H4(CO)2MnC(OC2H5)N(C2H5)2. This carbene complex reacts with borontrihalides BX3 (X = F, Cl) to yield [CH3C5H4(CO)2MnCN(C2H5)2]BX4. Ad-dition of [(C4H9)4N]F to this cationic carbyne complex results in the formation of CH3C5H4(CO)2MnC(F)N(C2H5)2 . In the same way C5H5(CO)2MnC(F)C6H5 is prepared from [C5H5(CO)2MnCC6H5]SbCl6. Fluoride addition can be reversed by reaction of the latter carbene complex with BF3 to give [C5H5(CO)2MnCC6H5]BF4. In the X-ray structure of C5H5(CO)2MnC(F)C6H5 unusual bonding parameters are found, which are consistent with the easy cleavage of the C(carbene)-F bond.