The thorium benzyne complex (η2-C6H4)ThCl3– was synthesized in the gas phase through consecutive decarboxylation and dehydrochlorination from the (C6H5CO2)ThCl4– precursor upon collision-induced dissociation. Theoretical calculations suggest that (η2-C6H4)ThCl3– exhibits a...

The uranyl(VI) benzyne complex (η 2 -C 6 H 4 )UO 2 Cl − was prepared in the gas phase by electrospray ionization mass spectrometry coupled with collision-induced dissociation. It was formed via a dual-ligand strategy that requires the elimination of benzoic acid or benzene/CO 2 from the uranyl dibenzoate precursor (C 6 H 5 CO 2 ) 2 UO 2 Cl − . This contrasts the known strategy for the formation of gas-phase benzyne complexes that would result from CO 2 /HCl elimination from (C 6 H 5 CO 2 )UO 2 Cl 2 − , during which only one benzoate ligand is involved. Such dual-ligand strategy can be extended to the preparation of a series of methyl-and halosubstituted benzyne complexes of uranyl(VI). Density functional theory calculations at the B3LYP level reveal that the benzyne complex (η 2 -C 6 H 4 )UO 2 Cl − features a metallacyclopropene structure with the C 6 H 4 2− ligand coordinated to uranium(VI) through two polarized U−C benzyne σ bonds, in accordance with the reactivity test toward water. Dehydrochlorination of the benzyne complex (η 2 -C 6 H 4 )UO 2 Cl − from (C 6 H 5 )UO 2 Cl 2 − that originates from decarboxylation of (C 6 H 5 CO 2 )UO 2 Cl 2 − with a single benzoate ligand is neither kinetically nor thermodynamically favorable than simple C 6 H 5 radical loss to give U V O 2 Cl 2 − . This arises from the presence of an accessible V oxidation state for uranium and accounts for the necessity for the dual-ligand strategy in the preparation of uranyl(VI) benzyne complexes from uranyl benzoate precursors.