Synthesis, Crystal Structure, and Properties of Mn(PO3F)(H2O)2

Single crystals of manganese(II) fluorophosphate dihydrate, Mn(PO3F)(H2O)(2), were grown in a metathesis reaction from aqueous solutions of MnCl2 and (NH4)(2)(PO3F). The crystal structure [P (1) over bar, Z = 2, a = 5.5280(7), b = 5.6357(7), c = 8.2570(10)angstrom, alpha = 81.279(2), beta = 75.156(2), gamma = 71.722(2)degrees, 1345 structure factors, 86 parameter, R[F-2 > 2 sigma(F-2)] = 0.0322, wR(F-2 all) = 0.0771] consists of [MnO4(H2O)(2)] octahedra that share a common edge to form isolated double octahedra of the type [Mn2O2/2O(4)/1(H2O)(4/1)]. Each double octahedron is bridged by the oxygen atoms of six (PO3F) tetrahedra to six neighboring double octahedra into a layered arrangement parallel to (001). Adjacent layers are held together through weak O-H center dot center dot center dot O hydrogen bonds, and no significant hydrogen bonding interactions of the type O-H center dot center dot center dot F are observed. Vibrational spectra are discussed in terms of a site-symmetry approximation for the (PO3F)(2)-anion. The thermal decomposition of Mn(PO3F)(H2O)(2) starts above 130 degrees C. In a multi-stage mechanism the end-product Mn2P2O7 is formed at temperatures above 500 degrees C. Magnetic measurements suggest an antiferromagnetic ordering of Mn(PO3F)(H2O)(2) at 3.4 K.