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Redox‐active arylazothioformamide (ATF) ligands, when reacted with CuI salts, coordinate to form a variety of 1 : 1 dimers and 2 : 1 ligand‐metal complexes through a N=N−C=S chelation motif. In this study, monosubstituted (ortho/meta/para) methoxy regioisomers of ATF were synthesized and evaluated with CuI halide and BF4 salts. UV‐Vis binding association studies revealed a 2 : 1 binding association model against all species producing a para ≫ ortho > meta pattern across the methoxy substitution range. To understand why the 2 : 1 non‐linear binding model was preferred over a 1 : 1 model for CuI halide salt dimers (i. e., A2B2), a series of mechanisms were computed indicating that metal salt dimers (i. e., B+B→B2) or ligand‐metal salt‐metal salt‐ (i. e., AB+B→AB2) interactions provide favorable pathways. Combined, the data substantiate the 2 : 1 binding association mechanistically even as the substitution pattern, steric bulk, and electronics alter the coordination strength of the ligands to the CuI center.

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Redox-active azothioformamide (ATF) ligands produce coordination complexes with Cu(I) salts. A series of monosubstituted ligands were used to synthesize Cu(I) complexes and investigated for the catalytic insertion of carbon dioxide into terminal alkynes. The optimal catalytic conditions were found using phenylacetylene with 4 mol % of a halogen-bridged (μ-I)-parasubstituted [(p-MeOATF-Cu(I)I)] 2 dimer with 3 equiv of Cs 2 CO 3 as the base in dimethyl sulfoxide under 1 atm of CO 2 at 40 °C for 24 h, followed by treatment with HCl. A variety of aryl and alkyl substrates were evaluated giving yields from 47 to 99%. The reaction was computationally deconstructed, and a series of likely intermediates and associated energies are provided along with a proposed mechanism. Additionally, it was found that the conditions were suitable for one-pot esterification.