A Synthetic, Structural, Spectroscopic, and Computational Study of Alkali Metal–Thioether, −Selenoether, and −Telluroether Interactions

The rigid thioether- and selenoether-containing pro-ligands,
4,5-bis(phenylsulfido)-2,7,9,9-tetramethylacridan
(H[AS2Ph2] (1)) and 4,5-bis(phenylselenido)-2,7,9,9-tetramethylacridan
(H[ASe2Ph2] (2)), were deprotonated
with one equiv of nBuLi to afford dimeric
lithium complexes [Li(AE2Ph2)]2 (E
= S (3), Se (4)) or with one equiv of KCH2Ph to afford the previously reported potassium complexes [K(AS2Ph2)(dme)]x (5) and [K(ASe2Ph2)(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[ASe2Tripp2] (7)) and 4,5-bis(2,4,6-triisopropylphenyltellurido)-2,7,9,9-tetramethylacridan
(H[ATe2Tripp2] (8)) were accessed
via the reaction of 4,5-dibromo-2,7,9,9-tetramethylacridan with three
equiv of nBuLi, 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(AE2Tripp2)(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.