The structures of tricarbonyl(formylcyclopentadienyl)manganese(I), [Mn(C6H5O)(CO)3], (I), and tricarbonyl(formylcyclopentadienyl)rhenium(I), [Re(C6H5O)(CO)3], (II), were determined at 100 K. Compounds (I) and (II)
both possess a carbonyl group in a trans position relative to the substituted C atom of the cyclopentadienyl ring, while the other two carbonyl groups are in almost eclipsed positions relative to their attached C atoms. Analysis of the intermolecular contacts reveals that the molecules
in both compounds form stacks due to short attractive π(CO)...π(CO) and π(CO)...π interactions, along the crystallographic c axis for (I) and along the  direction for (II). Symmetry‐related stacks are bound to each other by weak intermolecular C—H...O hydrogen
bonds, leading to the formation of the three‐dimensional network.