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

Crystals of potassium pentafluorophenolate dihydrate (PfpOK center dot 2H(2)O) have been obtained. The title compound formulated as [K(C6F5O)(H2O)(2)] crystallizes in monoclinic system, space group C2/c with a = 9.353(2), b = 18.329(6), c = 6.8679(17) angstrom, beta = 132.272(3)degrees, V = 871.2(4) angstrom(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) angstrom). 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.