(Ge4 Bi14 )4− : Ein Fall von “Element-Entmischung” auf molekularer Skala

Between Elemental Match and Mismatch: From K12 Ge3.5 Sb6 to Salts of (Ge2 Sb2 )2- , (Ge4 Sb12 )4- , and (Ge4 Sb14 )4

The solid mixture "K₂ GeSb" was shown to comprise single-crystalline K₁₂ Ge_3.5 Sb₆ (1), a double salt of K₅ [GeSb₃ ] with carbonate-like [GeSb₃ ]^5- anions, and the metallic Zintl phase K₂ Ge_1.5 . Extraction of 1 with ethane-1,2-diamine in the presence of crypt-222 afforded [K(crypt-222)]⁺ salts of several novel binary Zintl anions: (Ge₂ Sb₂ )^2- (in 2), (Ge₄ Sb₁₂ )^4- (in 3), and in the presence of [AuMePPh₃ ] also (Ge₄ Sb₁₄ )^4- (in 4). The anion in 2 represents a predicted, yet heretofore missing pseudo-tetrahedral anion. 4 comprises a cluster analogous to (Ge₄ Bi₁₄ )^4- and (Ga₂ Bi₁₆ )^4- , and thus one of the most Sb-rich binary p-block anions. The unprecedented cluster topology in 3 can be viewed as a defect-version of the one in 4 upon following a "dead end" of cluster growth. The findings indicate that Ge and Sb atoms are at the border of a well-matching and a mismatch elemental combination. We discuss the syntheses, the geometric structures, and the electronic structures of the new compounds.

Systematic DFT Studies on Binary Pseudo-tetrahedral Zintl Anions: Relative Stabilities and Reactivities towards Protons, Trimethylsilyl Groups, and Iron Complex Fragments

Binary pseudo-tetrahedral Zintl anions composed of (semi)metal atoms of the p-block elements have proven to be excellent starting materials for the synthesis of a variety of heterometallic and intermetalloid transition metal-main group metal cluster anions. However, only ten of the theoretically possible 48 anions have been experimentally accessed to date as isolable salts. This brings up the question whether the other species are generally not achievable, or whether synthetic chemists just have not succeeded in their preparation so far. To contribute to a possible answer to this question, global minimum structures were calculated for all anions of the type (TrTt3 )5- , (TrPn3 )2- , and (Tt2 Pn2 )2- , comprising elements of periods 3 to 6 (Tr: triel, Al⋅⋅⋅Tl; Tt: tetrel, Si⋅⋅⋅Pb; Pn: pnictogen, P⋅⋅⋅Bi). By analyzing the computational results, a concept was developed to predict which of the yet missing anions should be synthesizable and why. Additionally, the results of an electrophilic attack by protons or trimethylsilyl groups or a nucleophilic attack by transition metal complex fragments are described. The latter yields butterfly-like structures that can be viewed as a new form of adaptable tridentate chelating ligands.

Ge14 Br8 (PEt3 )4 : A Subhalide Cluster of Germanium

Heating a metastable solution of Ge^I Br to room temperature led to the first structurally characterized metalloid subhalide cluster Ge₁₄ Br₈ (PEt₃ )₄ (1). Furthermore 1 can be seen as the first isolated binary halide cluster on the way from Ge^I Br to elemental germanium, giving insight into the complex reaction mechanism of its disproportionation reaction. Quantum chemical calculations further indicate that a classical bonding situation is realized within 1 and that the last step of the formation of 1 might include the trapping of GeBr₂ units.

[SnBi3 ]5- -A Carbonate Analogue Comprising Exclusively Metal Atoms

The new [SnBi₃ ]^5- polyanion is obtained by the reaction of K₃ Bi₂ with K₄ Sn₉ or K₁₂ Sn₁₇ in liquid ammonia. The anion is iso(valence)electronic with and structurally analogous to the carbonate ion. Despite the high negative charge of the anion, the Sn-Bi bond lengths range between single and double bonds. Quantum-chemical calculations at a DFT-PBE0/def2-TZVPP/COSMO level of theory reveal that the partial double bond character between the heavy main-group atoms Bi and Sn originates from a delocalized π-electronic system. The structure of the anion is determined by single-crystal X-ray diffraction analyses of the compounds K₅ [SnBi₃ ] 9 NH₃ (1) and K₉ [K(18-crown-6)][SnBi₃ ]₂ ⋅15 NH₃ (2). The [SnBi₃ ]^5- unit is the first example of a carbonate-like anion obtained from solution, and it consists exclusively of metal atoms and completes the series of metal analogues of CO and CO₂ .