Germylyne complex [Cp*(OC)2Cr≡Ge{C(SiMe3)3}] (1) reacted with methyl vinyl ketone to give an η3-allyl complex 2 with an oxagermacyclopentenyl ring. An analogous η3-allyl complex 3 with a germacyclopentenyl ring was obtained by the reaction with butadiene, a non-polar conjugated molecule, under photoirradiation. These reactions are accompanied by cleavage of the Cr≡Ge triple bond. On the other hand, the reactions of complex 1 with alkynes under photoirradiation resulted in clean substitution of a CO ligand of 1 to afford (η2-alkyne)germylyne complexes, where the Cr≡Ge triple bond  is intact.