In conclusion, we have utilized the thermodynamic relationship between low-valent metal-protic ligand affinity and complex X-H BDFE to design the powerful PCET reductant SmBr2-NMEA. Subsequently, the SmBr2-NMEA reagent was shown to reduce a range of arenes as challenging as biphenyl and afforded facile conversion of alkynes to cis-alkenes. Moreover, SmBr2-NMEA mediated the rapid reduction of unactivated esters including 5-, 6-, and 7-membered lactones to their respective primary alcohols and diols. The intermediacy of the C-centered radical shown in Scheme 5 in the reduction of esters by SmBr2-NMEA was leveraged to afford 5-exotrig cyclization of a family of unactivated ester olefin substrates to cyclic alcohols. The reduction of substrates by SmBr2-NMEA that are typically recalcitrant to single electron transfer demonstrates the potential of chelation-promoted bond weakening to achieve difficult chemical transformations.