Crystal structures and Raman spectra of Cu(OH)F and Cu-3(OH)(2)F-4

Crystals of Cu(OH)F and Cu-3(OH)(2)F-4 have been synthesized at low-hydrothermal conditions in sizes up to 0.3 mm. The structures were solved from CCD X-ray single-crystal data and refined to R = 0.033 and 0.019, respectively. Cu(OH)F: space group P2(1)/a, Z = 4, a = 5.301 (1) Angstrom, b = 6.376(1) Angstrom, c = 5.074(1) Angstrom, beta = 112.90(1)degrees, and V = 157.98(5) Angstrom(3). Cu-3(OH)(2)F-4: space group P2(1)/n, Z = 2, a = 5.501(1) Angstrom, b = 4.766(1) Angstrom, c = 8.462(1) Angstrom, beta = 92.28(1)degrees, and V = 221.68(7) Angstrom(3). In both compounds the copper atoms are 4 + 2 coordinated to their ligands (Jahn-Teller distortion). Cu(OH)F is isotypic to Cu(OH)Cl, forming layers of edge-sharing Cu(OH)(3)F-3 polyhedra, which are interconnected by hydrogen bonds. The structure Of Cu-3(OH)(2)F-4 is characterized by chains of edge-sharing Cu(OH)(2)F-4 polyhedra running along [100], which are linked to each other via corners to form a framework. Hydrogen bonds of the type O-H...F occur with O...F distances of 2.619 and 2.697 Angstrom in Cu(OH)F and Cu-3(OH)(2)F-4, respectively. The observed O-H stretching frequencies of 3129 and 3306 cm(-1), respectively, in Raman spectra are in excellent agreement with expected values from distance - frequency correlations. Moreover, the pleochroism of the bands corresponds in both compounds to the O-H orientation found in the structure determination.