First Incorporation of the Tetrahedral [Sn₄]^4- Cluster into a Discrete Solvate Na₄[Sn₄] (NH₃)₁₃ from Solutions of Na₄Sn₄ in Liquid Ammonia

Abstract

Treatment of solutions of Na 4 Sn 4 in liquid ammonia with CuMes (Mes = mesityl) and 18-crown-6 afforded crystals of the composition Na 4 [Sn 4 ]·(NH 3 ) 13 . The structure features anionic units {Na 7 [Sn 4 ] 2 } and separate Na cations, both fully solvated by ammonia molecules.

Reactivity of Liquid Ammonia Solutions of the Zintl Phase K12Sn17 towards Mesitylcopper(I) and Phosphinegold(I) Chloride

“…[1] In the case of nine-atomic cluster compounds, a large variety of different complexes of this type have been reported, such as [(h 4 -Si 9 )ZnPh] 3À , [2] [(h 4 -Ge 9 )CuPiPr 3 ] 3À , [3] [(h 4 -Sn 9 )Cr(CO) 3 ] 4À , [4] [(h 4 -Sn 9 )Ir(cod)] 3À (cod = cyclooctadiene), [5] [(h 4 -Pb 9 )M(CO) 3 ] 4À (M = Mo, W), [6] [(h 1 -Si 9 ) 2 {Ni(CO) 2 } 2 ] 8À , [7] [(h 4 -Ge 9 )Cu(h 1 -Ge 9 )] 7À , [3] [(Ge 9 )Au 3 (Ge 9 )] 5À , [8] [Au 3 Ge 45 ] 9À , [9] or [Ag(Sn 9 ÀSn 9 )] 5À , [10] whereas only a limited number of complexes of tetrahedral clusters, such as [(MesCu) 2 (h 3 -E 4 )] 4À (E = Si, Ge), [11,12] mixed clusters in [(MesCu) 2 -(Si 4Àx Ge x )] 4À (x = 2.2(1)) [13] and [(h 2 -Sn 4 )Zn(h 3 -Sn 4 )] 6À[14] , are known. Recently, neat E 4 clusters (E = Si, Sn) have been characterized by 29 Si and 119 Sn NMR spectroscopy [15] and isolated as solvates, for example, in the compounds A 4 Sn 4 ·(NH 3 ) 2 (A = Rb, Cs), Rb 4 Pb 4 ·(NH 3 ) 2 , [16] and Na 4 Sn 4 ·(NH 3 ) 13 , [17] which offer new access to subsequent reactions of these clusters in solution.The second variant is that these clusters incorporate a transition metal, leading to the formation of endohedral cluster subunits. [18] Compounds such as [Co@Ge 10 ]…”

Stability and Conversion of Tin Zintl Anions in Liquid Ammonia Investigated by NMR Spectroscopy

“…Concerning Sn 4 4− , additive‐free solutions of Rb 4 Sn 4 never yielded Sn 4 4− in ammoniate structures due to the enhanced acidity of ammonia and therefore rapid oxidation of Sn 4 4− to Sn 9 4− by protons. Discrete [Na(NH 3 ) 5 ] + complexes should be even more acidic due to the smaller and harder sodium cation, but crystallization of the ammoniate Na 4 Sn 4 ⋅ 13 NH 3 ,4 obtained from cryptand‐free solvation experiments on Na 4 Sn 4 , suggests that the low solubility of some sodium Zintl compound ammoniates allows crystallization prior to oxidation. This hypothesis was supported during our NMR study, since during the direct reduction experiment with sodium, crystallization in the NMR tube prevented further investigation of the sample.…”

“…This preparation method is applicable for Group 14 (Sn, Pb) and Group 15 (P–Bi) elements and is the oldest method to generate homoatomic polyanions in solution 2. The number of compounds that have been crystallized from pure stannide solutions prepared by dissolution or direct reduction is rather small, and until now only A 4 Sn 4 ⋅ 2 NH 3 (A=Rb, Cs),3 Na 4 Sn 4 ⋅ 13 NH 3 ,4 Na 4 Sn 9 ⋅ 7 en (en=ethylenediamine),5 and [Li(NH 3 ) 4 ] 4 Sn 9 ⋅ NH 3 6 are known. In contrast, the number of compounds containing additional chelating ligands, such as 2.2.2‐cryptand or 18‐crown‐6 significantly exceeds the number of solvates of the pure binary compounds, which was attributed to enhanced solubility and better crystallization induced by the ligands 7.…”

Ammoniates of Zintl Phases: Similarities and Differences of Binary Phases A4E4 and Their Corresponding Solvates

“…We earlier reported on the crystal structures of Rb 4 Sn 4 •2NH 3 , Cs 4 Sn 4 •2NH 3 and Rb 4 Pb 4 •2NH 3 , which showed strong relations to the corresponding binaries [30]. In Na 4 Sn 4 •13 NH 3 [31,32] no such relation is observed. In general, ammonia in solid ammoniates is not only an innocent and largely unconnected solvent molecule but may also act as a ligand towards the alkali metal cations.…”

“…In the binary phases and Na 4 Sn 4 •13NH 3 [31,32] all triangular faces of the anions are capped η 3 -like by cations. In contrast, in A 4 E 4 •2NH 3 (A = K, Rb; E = Sn, Pb) [30] Table 4 summarizes the anion coordinations and it becomes evident that the solvate structures with a small content of ammonia molecules of crystallization are more similar to the solid state structure, thus the three-dimensional cation-anion interactions are considerably less disturbed.…”