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 structure was determined from single crystal diffraction data. This compound crystallizes in the monoclinic space group P21/c with a=11.956(2) ?, b=5.642(1) ?, c= 14.180(3) ?, beta=114°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 isostructural with perrierite Ce4Fe2 Ti3Si4O22, a naturally occurring sorosilicate mineral. The framework consists of rutile-like slabs formed of alternating chains of GeO6 octahedra and Mn3+O6 distorted octahedra, located between layers of mixed Ge1.2Si0.8O7 disilicates groups that separate the isolated Mn2 +O6 octahedra. A structural comparison with La4Mn5Si4O22 will be discussed.