Transfer of the carbyne ligand to the CC bond versus alkyne–carbyne–CO coupling in the reactions of [(η5-C5H5)(CO)2MnCPh]+ with electron-rich alkynes

The carbyne cation [(η5-C5H5)(CO)2MnCPh]+1 reacts with bis(diorganylamino)acetylenes by transfer of the carbyne ligand to the C–C bond of the alkynes to give cyclopropenyl cations; in contrast, the reaction with diorganylaminopropyne affords novel η4-carbene complexes by regioselective coupling of the carbyne and one CO ligand with the alkyne.