Synthesis, Structure, and Thermoelastic Properties of LiSn2Br3(CN2) and Sn4Br2(CN2)(3)

Abstract

Tin carbodiimides have been reported with various compositions, prepared via solid-state metathesis reactions by heating tin halides and lithium carbodiimide at moderate temperatures. The formations of two new compounds, LiSn2Br3(CN2) and Sn4Br2(CN2)(3) are monitored by differential thermal analysis (DTA), and crystal structures are reported as refined on basis of X-ray diffraction studies. The structure of LiSn2Br3(CN2) can be described by two interpenetrating frameworks of corner-linked coordination polyhedra, raising the possibility of negative thermal expansion (NTE) as investigated by density functional perturbation theory (DFPT). Like some previously reported tin carbodiimide compounds, LiSn2Br3(CN2) was also found to be a semiconductor with an indirect band gap of 2.5 eV, as determined by DFT calculations.