At this juncture, we envisioned that incorporation of an Ar-SF4 moiety on the BCP ring instead of SF5 would allow us to explore another concept in "hybrid isosterism," as the trans-substituted -SF4-linear architecture has been entertained as a replacement for an alkyne (or even a BCP ring). 25 This would also prove advantageous for further crystallographic analyses, as modification of the aryl group allows us to examine effects of remote substitution on the BCP ring. Under identical conditions to the reaction of SF5Cl with 1, we discovered that Ar-SF4Cl compounds can indeed be converted into the desired Ar-SF4-BCP-Cl products, albeit in modest yields. Thus, the reaction conditions were re-optimized explicitly for Ar-SF4Cl addition across 1. Note that, in this case, the reaction proceeds spontaneously in the dark at -45 ºC. The propensity of Ar-SF4Cl compounds to react more readily with 1 than SF5Cl is consistent with the fact that the S-Cl bond has been determined to be weaker in Ar-SF4Cl compounds (i.e., computed BDEs are on the order of 6-7 kcal/mol lower than the S-Cl BDE in SF5Cl). It is also known that both 1 and Ar-SF4Cl compounds, independently, can initiate radical chain propagations spontaneously in some cases in the absence of a designated radical initiator or other initiation source, such as light. F NMR yields are reported; isolated yields are in parentheses. (Bottom panel) Structural differences and select C and F NMR data associated with the linear array of atoms upon systematic alteration of electronic properties of the (hetero)arene. Structures determined by single-crystal X-ray diffraction (displacement ellipsoids depicted at 50% probability).