Ge₁₄Br_8–xCl_x(PEt₃)₄: Insight into the Reaction Route to Metalloid Clusters of Germanium

Abstract

The isolation of the germanium mixed halide cluster Ge 14 Br 8−x Cl x (PEt 3 ) 4 (2) by the reaction of a metastable Ge I Br solution (toluene/PEt 3 ) with GeCl 2 •dioxane provides new insights into the complex formation mechanism of metalloid germanium clusters through the disproportionation reaction of Ge I X (X = Cl and Br). It is shown that the Ge II halide is involved in at least two steps in the build-up reaction of 2. The molecular structure of 2 is presented together with a plausible reaction mechanism leading to the binary cluster Ge 14 Br 8 (PEt 3 ) 4 and future aspects of these findings.

Synthesis and Reactivity of Fluorenyl-Based Germanium(II) Compounds

“…The insertion of a germylene and the elimination of a Ge­(IV) compound are also assumed during the formation of Ge 14 Br 8 (PEt 3 ) 4 . The isolation of (Flu TMS ) 2 GeBr 2 7 is thus experimentally supporting the so far assumed reaction steps underlined by calculations . The reaction solution left behind still shows a dark red color, which is a sign of the formation of metal-rich compounds.…”

“…Since 2002, germanium compounds in oxidation state +I are accessible via the preparative cocondensation technique, as a metastable solution of monovalent germanium halides (GeX in toluene/PR 3 ; X = Cl, Br; R = alkyl-substituted). , The availability of a metastable solution of GeX opened a new way to synthesize metalloid clusters (Ge m R n , m > n ), , with up to 14 germanium atoms ([Li­(THF) 2 ] 3 [Ge 14 (E­(SiMe 3 ) 3 ] 5 ; E = Ge, Si). , In this procedure, metalloid clusters are accessed by disproportionation of the GeX solution and insertion of sterically demanding substituents via salt metathesis simultaneously. , Insights into possible Ge n X m intermediates during the disproportionation of GeX to elemental germanium and compounds of germanium with an oxidation state higher than +1 have so far only been afforded by the isolation of the first subhalide cluster Ge 14 Br 8 (PEt 3 ) 4 , obtained by heating a metastable solution of GeBr (toluene/PEt 3 ) . Follow-up studies led to the conclusion that the insertion of germylenes GeR 2 (R = organic substituent) is an important step during the cluster build-up reaction …”