Mixed Ligated Tris(amidinate)dimolybdenum Complexes as Catalysts for Radical Addition of CCl<sub>4</sub> to 1‑Hexene: Leaving Ligand Lability Controls Catalyst Activity


We synthesized a series of mixed ligated tris­(amidinate)­dimolybdenum complexes, namely, [Mo<sub>2</sub>(DAniF)<sub>3</sub>(L)] [DAniF = <i>N</i>,<i>N</i>′-di­(<i>p</i>-anisyl)­formamidinate; L = acetate (OAc; <b>1a</b>), <i>m</i>-diphenylphosphino benzoate (<i>m</i>-PPh<sub>2</sub>Bz; <b>1b</b>), nicotinate (Nico; <b>1c</b>), benzoate (Bz; <b>1d</b>), 3-furoate (3-Furo; <b>1e</b>), isonicotinate (IsoNico; <b>1f</b>), and trifluoromethanesulfonate (OTf; <b>1g</b>)], which served as catalysts for radical addition of CCl<sub>4</sub> to 1-hexene to give 1,1,1,3-tetrachloroheptane. These mixed ligated complexes <b>1a</b>–<b>g</b> afforded the higher yield of the radical addition product than a homoleptic DAniF complex, [Mo<sub>2</sub>(DAniF)<sub>4</sub>] (<b>2</b>). Among them, complexes <b>1a</b> and <b>1g</b> gave the radical addition product quantitatively after 9 h with a short induction period. When complexes <b>1a</b> and <b>1g</b> were treated with CCl<sub>4</sub>, we detected the mixed-valence Mo<sub>2</sub>(II/III) complex, [Mo<sub>2</sub>(DAniF)<sub>3</sub>Cl<sub>2</sub>] (<b>4</b>), in electrospray ionization mass spectrometry measurements, indicating that the leaving nature of the L ligands was a crucial factor for initiating the catalytic reaction: the catalytic activity of the carboxylate-bridged complex <b>1a</b> and the triflate-bridged complex <b>1g</b> in the initial 30 min highly depended on the ligand-exchange rate of L, as estimated by monitoring the reaction with CCl<sub>4</sub> in pyridine, giving the pyridine adduct complex, [Mo<sub>2</sub>(DAniF)<sub>3</sub>Cl­(py)] (<b>3</b>)

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