Activation parameters demonstrate a low barrier to bondreorganization and an organized transition state. Taken together, these data are consistent with previous studies of Sm(II)-proton donor systems where substrate reduction occurs through CPET. Previous collaborative work from our group demonstrated that Sm(II) is more azaphilic than oxophilic. The presence of nitrogen in NMEA is likely responsible for the strong coordination between the ligand and metal. One question that remains is: Does H-transfer originate from the N-H or O-H bond? First, a previous study demonstrates that H-transfer in arene reduction occurs from DMEA, a chelating ligand with no coordinated N-H bond. Second, ethylenediamine, which is expected to coordinate more strongly, does not lead to substrate reduction. Finally, substitution on the N or O of coordinating alcohols and amines inhibits coordination to Sm(II). As a consequence, while nitrogen coordination enhances chelation to Sm(II), the more acidic proton from the bound O-H of NMEA is the likely source of hydrogen in substrate reduction. With this analysis in hand, we examined a series of substrates that are typically recalcitrant to ET from Sm(II). Three alkynes, 6-dodecyne, 5-decyne, and 4-decyne were reduced to the cis products in 92, 88, and 58% yields respectively as shown in Scheme 3 below. The balance of each reaction was unreduced starting material and a small amount of alkane.