Reaction of the digermyne Ar'GeGeAr' (1) with ONC6H4-2-CH3 affords a unique example of an unsymmetric singlet diradicaloid, the oxo/imido-bridged species Ar'Ge(mu-O)(mu-NC6H4-2-CH3)GeAr' (2), which was characterized by spectroscopy, X-ray crystallography, and density functional theory computations. The direct reaction of 1 with O-2 to generate the symmetric diradicaloid Ar'Ge(mu(2)-O)(2)GeAr' led to the double-addition product Ar'Ge(mu(2)-O)(2)(eta(1),eta(1):mu(2)-O-2)GeAr' (8), which was also characterized structurally and spectroscopically. Calculations on simple models showed that the HOMO-LUMO energy gap decreases as the imido bridges in MeGe(mu-NH)(2)GeMe are replaced by oxygens, which is consistent with the higher reactivity of Ar'Ge(mu(2)-O)(2)GeAr' toward further O-2 addition.