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The syntheses of two new ligands containing macrocyclic [10]-aneNS2 (1-aza-4,8-dithiacyclodecane) units are reported, including the N-methylated analogue (L^Me) and a dinucleating version that separates two [10]-aneNS2 groups with a m-xylyl spacer (L²). Copper complexes with these new ligands as well as previously reported related complexes have been found to mediate the aziridination of olefins. Thus, isolated copper complexes containing the ethylnaphthyl-appended [10]-aneNS2 macrocyclic ligand (L^nap), including [L^napCu]PF6 (1) and [L^napCu(CH3CN)]PF6 (2), the Cu(I) complex [L^MeCu(CH3CN)]PF6 (3), and the Cu(II) complex L^MeCuBr2 (4), were compared in their ability to function as aziridination precatalysts. In addition, the aziridination capabilities were probed for complexes generated in situ from copper(I) ion sources and L², 1,4,7-triazacyclononane, 1,4,7-trithiacyclononane, or 1,4,7-trimethyl-1,4,7-triazacyclononane. The synthesis and characterization of the new complexes 3 and 4 are reported, including X-ray crystal structures. The aziridination reaction using precatalyst 3 was examined for its tolerance to different functional groups near the olefin as well as to the use of other nitrogen group sources and reaction conditions.

Variable-temperature one- and two-dimensional NMR experiments with [LCu](PF6) (L = N-(2-(1-naphthyl)ethyl)-1-aza-4,8-dithiacyclodecane) reveal solution binding of the pendant naphthalene group, consistent with the η² binding found in the solid-state structure. The free energy for the barrier to the process that involves coordination/decoordination of the naphthalene group was estimated to be 12−13 kcal/mol.