Redetermination of the crystal structures of the hexahydroxometallates Na2Sn(OH)(6), K2Sn(OH)(6), and K2Pb(OH)(6)

Slow cooling down of hot saturated hydroxo stannate- reap. -plumbate soluti ons gives crystals of Na2Sn(OH)(6), K2Sn(OH)(6), and K2Pb(OH)(6) well suite d for an X-ray structure determination. With these crystals the so far know n crystal data were verified, determined more precisely and H-positions fou nd for the first time. The compounds crystallize rhombohedral in the space group R (3) over bar. The hexagonal unit cells contain three formula units with Na2Sn(OH)(6): a = 5.951(1) Angstrom, c = 14.191(2) Angstrom, c/a = 2.384 K2Sn(OH)(6): a = 6.541(1) Angstrom, c = 12.813(4) Angstrom, c/a = 1.959; K2Pb(OH)(6): a = 6.625(1) Angstrom, c = 12.998(2) Angstrom, c/a = 1.962 The compounds are not isotypic whereas the atoms occupy in all three cases the same Wyckoff positions. Na2Sn(OH)(6) has with an hcp packing of O a CdI 2 like superstructure with Na and Sn in octahedral interstices. Hydrogen bonds O-H ... O-H play a role in solid K2Sn(OH)(6) and K2Pb(OH)(6) . Zn these compounds the potassium ions are shifted from an octahedral coor dination in an hcp packing of O. They have nine nearest Q-neighbours. The h ydrogen bonds are investigated by Raman spectroscopy.