Leucophosphite K[Fe2(PO4)2(OH)(H2O)]•H2O:: Hydrogen bonding and structural relationships

Hydrogen atom positions in leucophosphite K[Fe-2(PO4)(2) (OH)(H2O)]. H2O mere elucidated by Rietveld refinement of a powder neutron scattering diffractogram, Crystal data: a = 975.6(3), b = 966.4(3), c = 976.9(4) pm, beta = 102.43(2)degrees, R-wp = 0.084. This experiment proved that the Fe-atoms in the tetrameric Fe4O2 building units of leucophosphite are bridged by hydroxo groups and that the phosphate tetrahedra are not protonated, While the water molecule O (10) bound to Fe acts only as a H-bond donor, the second water molecule O (11) between the tetrameric units donates and accepts H-bonds, Together with oxygen atoms from phosphate groups a six-membered ring of oxygen atoms, connected by hydrogen bonds, is formed, Water O (11) is held in the structure b comparably weak H-bonds so that it is already lost at 396(3) K. Fe4O2 tetramers topological analogous to those in leucophosphite are found in the minerals spheniscidite, melonjosephite, and amarantite, and in a number of synthetic iron complexes, The structural relationships of leucophosphite with compounds containing M4O2 clusters (M = Al, Ga, Mo) are discussed. (C) 1997 Academic Press.