Synthesis and structural characterization of La4Mn3Ge5.2Si0.8O22, a new compound with the perrierite structure

A new layered germanate La4Mn3Ge5.2Si0.8O22 has been prepared and its struc ture was determined from single crystal diffraction data, This compound cry stallizes in the monoclinic space group P2(1)/c with a 11.955(2) Angstrom, b = 5.642(1);Angstrom, 14.180(3) Angstrom, beta = 114 degrees 09(3), and Z = 2 formula units by cell. The structure has been refined to residuals of R = 3.14% for 1380 observations and 152 parameters. La4Mn3Ge5.2Si0.8O22 is i sostructural with perrierite Ce4Fe2Ti3Si4O22, a naturally occurring sorosil icate mineral. The framework consists of rutile-like slabs formed of altern ating chains of GeO6 octahedra and Mn3+O6 distorted octahedra, located betw een layers of mixed Ge1.2Si0.8O7 disilicates groups that separate the isola ted Mn2+O6 octahedra. A structural comparison with La4Mn5Si4O22 will be dis cussed. (C) 1999 Academic Press.