Synthesis and characterisation of the quaternary cyanamide Li₂MgSn₂(NCN)₆

Abstract

The quaternary cyanamide Li 2 MgSn 2 (NCN) 6 was prepared by a solid-state metathesis reaction between Li 2 NCN, MgF 2 , and SnF 4 . Its trigonal structure was determined from powder X-ray diffraction data to be isotypic to that of Li 2 MnSn 2 (NCN) 6 with P31m symmetry. The new phase is well thought of as being derived from a [NiAs]-type MNCN structure with Sn 2 (NCN) 3 2 + corundum-like layers alternating with Li 2 Zr(NCN) 3 -like Li 2 Mg-(NCN) 3 2À layers. Structural anomalies in the shape of the cyanamide units are addressed via PXRD, IR spectroscopy as well as density-functional theory, all of them suggesting the presence of N�CÀ N 2À cyanamide units.

Synthesis, crystal structures and semiconducting properties of new hexacyanidometallates

“…3b), with 1̄ site symmetry, shows Mg–N bond distances of about 2.18, 2.30, 2.43 Å congruent with the literature examples. 27,28 The N–Mg–N angles in Na 2 [MgFe(CN) 6 ] range from 88.4(7) to 93.1(7), thereby reflecting a slightly distorted MgN 6 octahedra. The FeC 6 octahedra have the same site symmetry but are even more distorted (Fig.…”

“…The quasi octahedron MgN 6 (Fig. 3b), with 1 ˉsite symmetry, shows Mg-N 27,28 The N-Mg-N angles in Na 2 [MgFe (CN) 6 ] range from 88.4 (7) to 93.1 (7), thereby reflecting a slightly distorted MgN 6 octahedra. The FeC 6 octahedra have the same site symmetry but are even more distorted (Fig.…”

Ion transport mechanism in anhydrous lithium thiocyanate LiSCN Part I: ionic conductivity and defect chemistry

“…Apart from recently prepared tri-cationic cyanamides with the composition Li 2 MSn 2 (NCN) 6 (M = Mg 45 und Mn 46 ), anhydrous thiocyanates, nitrides or cyanides of lithium and any divalent transition metal are unknown so far, which makes the structure of Mg 1.02 Li 3.96 (SCN) 6 a hitherto unknown structure type (details in the ESI†). Mixed alkali and alkaline earth metal pseudo -halides are rare, 47–49 and even though Na 4 Mg(SCN) 6 has a very similar composition, its crystal structure is very different.…”

The [NCN]2– Carbodiimide Complex Anion and Its Compounds–A “Divalent Nitride” Unit for Nitridocarbonates in Materials and Applications

“…These analogues of the ubiquitous AM O 3 oxides crystallize in chiral structures ( P 6 3 22) with an intraplanar cation/vacancy ordering scheme that is very similar to that of ferroelectric LiNbO 3 ( R 3 c ). The final important group of [NiAs]-derived metal nitridocarbonates to mention are a series of isostructural quaternaries: Li 2 M Sn 2 (NCN) 6 ( M = Mn and Mg) and Na 2 M Sn 2 (NCN) 6 ( M = Mn, Fe, Co and Ni). − This structure-type is characterized by two distinct metal sheets, with corundum-like [Sn 2 (NCN) 3 ] 2+ layers alternating with [A 2 M (NCN) 3 ] 2– layers, resulting in a highly asymmetric coordination of [N–CN] 2– with a strong degree of cyanamide character. Furthermore, these are the first examples of metal nitridocarbonates to contain both alkali metal cations and redox-active transition metal cations, opening up the tantalizing prospect of oxidative (de)intercalation chemistry (see also electrochemistry section).…”