The synthesis and characterization of the metalloid germanium clusters {Ge 9 [Si(SiMe 3 ) 2 (SiPh 3 )] 2 } 2-(1), {Ge 9 [Si-(SiMe 3 ) 3 ][Si(SiMe 3 ) 2 (SiPh 3 )] 2 } -(2), {Ge 9 [Si(SiMe 3 ) 2 (SiiPr 3 )] 3 } -( 3), and [Ge 9 (SiHtBu 2 ) 3 ] -(4), which were obtained by the reaction of the Zintl anion Ge 9 4with different silyl halides, are presented.[a]
805Compound 4 is the sterically least protected soluble Ge 9 R 3 cluster known to date, and thus has interesting structural features and may open the way to new coordination modes of metalloid Ge 9 R 3 clusters.
The reaction system GeCl2⋅dioxane/LiSTsi (Tsi=C(SiMe3)3) opens a fruitful area in germanium chemistry, depending on the stoichiometry and solvent used during the reaction. For example, the reaction of GeCl2⋅dioxane in toluene with two equivalents of the thiolate gives the expected germylene Ge(STsi)2 in excellent yield. This germylene readily reacts with hydrogen and acetylene, however, in a non‐selective way. By using an excess amount of the thiolate and toluene as the solvent, the germanide [Ge(STsi)3][Li(thf)] is obtained. Performing the same reaction in thf leads to a C−H activation of thf to give (H7C4O)Ge[STsi](μ2‐S)2Ge[STsi]2, in which the thf molecule is still intact. Using a sub‐stoichiometric amount of the thiolate leads to the heteroleptic compound [ClGe(STsi)]2 and to the insertion product (thf)Ge[S‐GeCl2‐Tsi]2, in which additional GeCl2 molecules insert into the C−S bonds of Ge(STsi)2. The synthesis and the experimentally determined structures of all compounds are presented together with first reactivity studies of Ge(STsi)2.
Heating a metastable solution of Ge Br to room temperature led to the first structurally characterized metalloid subhalide cluster Ge Br (PEt ) (1). Furthermore 1 can be seen as the first isolated binary halide cluster on the way from Ge 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 GeBr units.
Classical halides of the heavier Group 14 homologues germanium, tin, and lead are common precursors for the synthesis of exciting compounds, such as polyhedral clusters. To get access to larger metalloid cluster compounds of Group 14, the disproportionation reaction of metastable monohalide solutions, accessible through a preparative co‐condensation reaction, proved to be quite successful. As the identity of the subvalent halides within the metastable solutions were yet unknown the reaction course from a monohalide precursor to a metalloid cluster was mostly unidentified. This might change now, as a first subhalide cluster [Ge14Br8(Et3P)4] could be characterized, being the first trapped intermediate of the disproportionation reaction of Group 14 subhalides. All these aspects are included within this Minireview, together with a short historical overview, dealing with the development of the preparative co‐condensation technique out of the matrix isolation technique, being the essential first step of the synthesis of metastable monohalide solutions of the heavier Group 14 elements Ge and Sn.
The reaction of GeCl 2 •dioxane with 2 equiv of the thiolate LiSHyp [Hyp = Si(SiMe 3 ) 3 ] yields the germanide (12-crown-4) 2 Li[Ge(SHyp) 3 ] (1). A small structural variation in the substituent leads to a completely different result because the reaction of GeCl 2 •dioxane with 2 equiv of the thiolate KSHyp Ph 3 [Hyp Ph 3 = Si(SiMe 3 ) 2 (SiPh 3 )] in toluene yields the unexpected compound 2) in high yield. The reaction cascade to give 2 includes several rearrangement reactions and an intramolecular [2 + 4] cycloaddition of a phenyl ring. The syntheses and molecular structures of both compounds are presented, together with quantum-chemical calculations and NMR measurements, to enlighten the reaction mechanism behind the formation of 2.
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