Discrete organoselenolate anions: Preparation and crystal structures of tetraphenylphosphonium 2-thienylselenolate and 2-furylselenolate

Abstract

The reactions of LiSeR (R = 2-thienyl, Th or 2-furyl, Fu) with PPh₄Br afford isomorphic tetraphenyl (2-thienylselenolate) (1) or (2-furylselenolate) (2) in relatively good yields. In the former reaction, a small amount of (Ph₄P)(SeTh) · H₂O (1 · H₂O) was also obtained. Both (Ph₄P)(SeTh) (1) and (Ph₄P)(SeFu) (2) are monoclinic, space group P2₁/n. The unit cell of 1 is a = 10.746(2), b = 13.353(3), c = 16.954(3) Å, β = 108.01(3)° and that of 2 is a = 10.484(2), b = 13.286(3), c = 16.900(3) Å, β = 108.13(3)°. The thienylselenolate and furylselenolate anions in 1 and 2 are located between the Ph₄P⁺ cations and there is no association between the cations and the anions or between the anions. By contrast, in 1 · H₂O (a = 8.879(2), b = 14.257(3), c = 19.883(4) Å, β = 91.84(3)°, space group P2₁/c) the anions are associated as dimeric units by weak hydrogen bonds between the selenium atoms of the selenolate and hydrogen atoms of two water molecules. These dimeric units form layers of skewed stacks between the Ph₄P⁺ cations.