This work was originally motivated by the methodological advancement of forging novel C(sp 3 )-SF5 and C(sp 3 )-SF4Ar bonds through strain-release functionalization of [1.1.1]propellane. As SF5-BCP and -SF4-BCP motifs were recognized in this study as types of potential "hybrid isosteres" (for [CF3/t-Bu + Ph] and [alkyne + Ph], respectively), this prompted detailed SC-XRD studies that led to the discovery and additional investigations of short transannular C•••C distances. Lastly, DFT calculations and previous literature support the notion that donor-acceptor interactions involving the wing C-C bonds in BCP rings play a significant role (alongside linear through-space interactions) in this shortening phenomenon. The theoretical model was corroborated by X-ray data, 37 whereby manifestations of these "wing donation" effects were observed in solid-state structures. Following this critical proof of concept and detailed structural study, future work will pertain to installing SF5-BCP and ArSF4-BCP motifs onto more complex molecules and evaluating applications.