Crystal Structure of Hydrated Potassium Pentafluorophenolate: Interactions Between Fluorine Atoms and Metal Ions

AbstractCrystals of potassium pentafluorophenolate dihydrate (PfpOK · 2H 2 O) have been obtained. The title compound formulated as [K(C 6 F 5 O)(H 2 O) 2 ] crystallizes in monoclinic system, space group C2/c with a = 9.353(2), b = 18.329(6), c = 6.8679(17) Å, β = 132.272(3)°, V = 871.2(4) Å 3 , Z = 4. The main features of the structure are the aromatic stacking of PfpO − with opposite dipole orientation and, more astonishing, coordination of the metal to fluorine atoms instead of the expected bonding to the phenolate oxygen atom (shortest PfpO-K distance = 4.357(1) Å). The coordination sphere of the K cation contains four water molecules and four F atoms. The phenolate oxygen binds to four water molecules through hydrogen-bonding. B3LYP/6-31+G(d) calculation suggest a charge of −0.69 for O1 versus −0.39, −0.38 and −0.40 for the fluorines atoms respectively, providing insight into the unusual bonding modes.Graphical AbstractCrystals of potassium pentafluorophenolate dihydrate (PfpOK·2H 2 O) show unusual anti-parallel aromatic stacking of PfpO − and, even more astonishing location of the octa-coordinated K + remote from the oxygen anion.[IMAGE]