HF adducts of alkali metal hydrogen salts with the F-H center dot center dot center dot O type of hydrogen bond: Synthesis and crystal structures

Crystalline adducts of acid salts with hydrogen fluoride K-3(SO4)(HSO4) . 2 HF (I), CsH2PO3 . HF (II), and CS4(SeO4)(HSeO4)(2) . HF (III) were synthesi zed. The crystal structures of the compounds were determined by single-crys tal X-ray diffraction analysis at 180 K; for I: a = 20.567(6) Angstrom, b = 6.177(2) Angstrom, c = 8.257 (3) Angstrom, beta = 109.18(4)degrees, space group C2, R-1 = 0.0236; for II: a = 5.581(2) Angstrom, b = 4.863(2) Angstro m, c = 18.400(7) Angstrom, beta = 92.09(3)degrees, space group P2(1)/c, R-1 = 0.0251; for III: a = 25.413(5) Angstrom, b = 12.718(3) Angstrom, c = 10. 819(2) Angstrom, beta = 107.57(3)degrees, space group C2/c, R-1 = 0.0276. I n addition to standard O-H...O hydrogen bonds, shorter F-H...O bonds (2.36- 2.44 Angstrom) exist in the structures studied. Compound I is structurally built of dimeric [H(SO4)(2)](3-) anions, two HF molecules being attached to each of them. In II, H2PO3- anions are O-H...O hydrogen-bonded to form zig zag chains with HF molecules as branches. In the structure of III, the HF m olecules are attached to trimers composed of one SeO42- group and two HSeO4 - groups.