Single‐Crystal Structure Determination and Solid‐State NMR Investigations of Lithium Nitridosilicate Li₂SiN₂ Synthesized by a Precursor Approach Employing Amorphous “Si(CN₂)₂”

Abstract

Abstract Amorphous silicon bis(carbodiimide) “Si(CN 2 ) 2 ” has been identified as a reactive precursor for the synthesis of nitridosilicates that is specifically useful in the temperature region below 1000 °C. In this context the applicability and reactivity of amorphous “Si(CN 2 ) 2 ” towards Li 3 N in comparison to silicon diimide Si(NH) 2 has been studied using high‐temperature in situ powder diffraction and DSC measurements. During the current investigation single crystals of Li 2 SiN 2 have been obtained and the crystal structure of this Li + ion conductor has been determined and refined: [ Pbca , no. 61, a = 9.907(2), b = 9.907(2), c = 15.014(3) Å, Z = 32, R 1 = 0.038, 1460 data, 142 parameters]. In the solid, Li 2 SiN 2 consists of two interpenetrating cristobalite type nets which are made up from hetero‐adamantane‐like [Si 4 N 6 ]N 4/2 groups. The eight crystallographically independent Li + sites are ordered at room temp. and exhibit coordination numbers 3 to 5. The 7 Li and 29 Si solid‐state MAS NMR spectra of Li 2 SiN 2 are reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)