Synthesis, Structure, and Electronic Properties of Sn(CN₂) and Sn₄Cl₂(CN₂)₃

Abstract

A solid-state metathesis reaction between equimolar amounts of Li2(CN2) and SnCl2 revealed the formation of two new compounds, Sn4Cl2(CN2)3 and Sn­(CN2). Thermal analysis of this reaction indicated that Sn4Cl2(CN2)3 forms exothermically near 200 °C and subsequently transforms into Sn­(CN2) at higher temperatures. The crystal structures of both compounds are presented. According to optical measurements and band structure calculations, Sn­(CN2) can be considered as a semiconductor with a band gap on the order of 2 eV. The presence of Sn2+ ions in the structure of Sn­(CN2) with a toroidally shaped lone pair is indicated by electron localization function calculations. The structure of Sn­(CN2) is shown to be related to the structures of FeS2 and CaC2.

SnCN2: A Carbodiimide with an Innovative Approach for Energy Storage Systems and Phosphors in Modern LED Technology

“…The sample, not being air sensitive, was enclosed in a glass capillary with 0.3 mm diameter. Our structure model is consistent with the work of Löber et al, [41] except that they have chosen to use the nonstandard setting I2/a space group to have the monoclinic angle closer to 90°. The observed and calculated X-ray powder diffraction patterns as well as their difference curves after Rietveld refinement [55] are shown in Figure 1.…”

“…The presence of Sn 3 N 4 , as evidenced by XRD and Mössbauer spectroscopy, might lead to an improved capacity retention as it can act as a buffer to accommodate the strong volume changes during the conversion reaction of SnCN 2 . Overall, the voltage profile observed during galvanostatic cycling shows some similarity to that observed for SnO [68] that has a structure similar to that of SnCN 2 , [41] and therefore a similar reaction mechanism can be expected, vide infra.…”

“…While Sn(SCN) 2 [38] has been identified for many years now, just recently new attempts have been made to find SnCN 2 , which led to Sn 2 O(CN) 2 . [39] Now simultaneously with our patent [40] a new paper of Löber et al [41] just recently appeared indicating the formation of SnCN 2 via the intermediate compound Sn 4 Cl 2 (CN 2 ) 3 . From the application perspective, there are up to now consequently no reports on the materials properties of SnCN 2 ; especially concerning potential luminescence behavior and energy storage investigations.…”

“…This cross linking leads to a three dimensional network in SnCN 2 , while in Pb (CN) 2 [21] separated layers of Pb-(N=C=N) 2À rhombs are found. Comparing the structures of some Sn-containing carbodiimide family members namely the ones of SnCN 2 , Sn 2 O(CN) 2 , [39] Sn(SCN) 2 [38] and Sn 4 Cl 2 (CN 2 ) 3 , [41] it becomes obvious that the structure motifs of SnCN 2 and Sn 2 O(CN) 2 [39] are very similar, while Sn(SCN) 2 [38] and Sn 4 Cl 2 (CN 2 ) 3 [41] display a completely differ-ent pattern. (see Figure 3) The crystal structures of SnCN 2 and Sn 2 O(CN) 2 [39] are characterized by a three-dimensional network of Sn 2 + cations and (N=C=N) 2À anionic groups.…”

“…Finally, both crystal structures of SnCN 2 and Sn 2 O [39] (standard deviations in parentheses). [39] view along [001], c) Sn (SCN) 2 [38] view along [010] and d) Sn 4 Cl 2 (CN 2 ) 3 [41] view along [100]. (Sn atoms in light blue, C atoms in red, Cl in green, N atoms in blue and O atoms in violet .)…”