A Synthetic, Structural, Spectroscopic, and Computational Study of Alkali Metal-Thioether, -Selenoether, and...

The rigid thioether- and selenoether-containing pro-ligands, 4,5-bis(phenylsulfido)-2,7,9,9-tetramethylacridan (H[AS₂^Ph2] (1)) and 4,5-bis(phenylselenido)-2,7,9,9-tetramethylacridan (H[ASe₂^Ph2] (2)), were deprotonated with one equiv of BuLi to afford dimeric lithium complexes [Li(AE₂^Ph2)]₂ (E = S (3), Se (4)) or with one equiv of KCH₂Ph to afford the previously reported potassium complexes [K(AS₂^Ph2)(dme)] (5) and [K(ASe₂^Ph2)(dme)₂] (6). Attempts to prepare a direct telluroether analogue of compounds 1-2 were unsuccessful. However, the bulky selenoether- and telluroether-containing pro-ligands 4,5-bis(2,4,6-triisopropylphenylselenido)-2,7,9,9-tetramethylacridan (H[ASe₂^Tripp2] (7)) and 4,5-bis(2,4,6-triisopropylphenyltellurido)-2,7,9,9-tetramethylacridan (H[ATe₂^Tripp2] (8)) were accessed via the reaction of 4,5-dibromo-2,7,9,9-tetramethylacridan with three equiv of BuLi, followed by the addition of two equiv of the corresponding diaryl dichalcogenide and quenching with dilute HCl_(aq). The new selenoether- and telluroether-containing pro-ligands were subsequently deprotonated using KCH₂Ph to afford [K(AE₂^Tripp2)(dme)₂] (E = Se (9), Te (10)). Compounds 1-10 were characterized by ¹H, ¹³C{¹H}, ⁷⁷Se{¹H}, ¹²⁵Te{¹H}, and ⁷Li NMR spectroscopy, where applicable, and single-crystal X-ray structures were obtained for all lithium and potassium complexes (3-6 and 9-10). DFT calculations were also performed to assess the nature of bonding between the hard group 1 cations and the soft chalcogenoethers.