Basic Reactivity Pattern of a Cyclic Disilylated Germylene

Abstract

In order to estimate the reactivity of disilylated germylene phosphine adducts, a cyclic version of this compound class was reacted with a number of different reagents. Reactions with the chalcogens sulfur, selenium, and tellurium led to dimers of the heavy ketone analogues. Reactions with water and ethyl bromide proceeded to give the respective oxidized germanol and germyl bromide. Two different reactions with alkynes were observed which led either to a germacyclopropene, by addition of tolane to the germylene, or to a silagermacyclobutene, likely formed by addition of the alkyne across a silagermene. Reaction via the silagermene was also observed in the reaction with benzophenone. Reaction of a germylene phosphine adduct with GeCl2·(dioxane) provided insertion of the silylated germylene into a Ge–Cl bond, leading to a germylated chlorogermylene phosphine adduct.

Alkyne Addition and Insertion Reactions of [(Me3Si)3Si]2Ge⋅PMe3

“…More recently, we reported that reactions of 2 a and related cyclic compounds with tolane form germacyclopropenes . Conversely, the reaction of 2 a with phenylacetylene gives vinylgermylene 10 a , the product of a regio‐ and stereoselective insertion into a Ge−Si bond (Scheme ) …”

“…Based on initial studies with cyclic disilylated stannylenes and plumbylenes, our work included PEt 3 and PMe 3 adducts of some cyclic disilylated germylenes and the recent synthesis of PMe 3 and NHC adducts of bis[tris(trimethylsilyl)silyl]germylene …”

“…[14] However,r ecently NHC adducts of at ris(trimethylsilyl)silylchlorogermylene and bis[tris(trimethylsilyl)stannyl]germylene were reported. [15] Based on initial studies with cyclic disilylated stannylenes [16] and plumbylenes, [17] our work included PEt 3 and PMe 3 adducts of some cyclic disilylatedg ermylenes [18][19][20][21] and the recent synthesis of PMe 3 and NHC adducts of bis[tris(trimethylsilyl)silyl]germylene. [6] The synthesis of 2a,w hich is the PMe 3 adduct of bis[tris(trimethylsilyl)silyl]germylene 2,was accomplished in astraightforward way by reaction of tris(trimethylsilyl)silylpotassium (1) with GeCl 2 ·dioxane in the presence of PMe 3 (Scheme1).…”

Revealing Germylene Compounds to Attain Superbasicity with Sigma Donor Substituents: A Density Functional Theory Study

“…This PA value is comparable to that for methylamine bases . Therefore, it appears that germylene derivatives can also achieve much higher basicity with suitable substituents, although the PA value of germylene is lower than its lower homologue (carbene and silylene) owing to the reluctance of donation of lone‐pair electron . To augment the basicity of Ge II , isopropyl groups were introduced into system 4 and the calculated PA was found to be 225.0 kcal mol −1 (Table ).…”

“…[70] Therefore, it appears that germylene derivatives can also achieve much higherb asicity with suitable substituents, although the PA value of germylene is lower than its lower homologue (carbene and silylene) owing to the reluctance of donation of lone-pair electron. [71] To augment the basicity of Ge II ,i sopropyl groupsw ere introduced into system 4 and the calculated PA was found to be 225.0 kcal mol À1 ( Table 2). These results suggest that bettere lectron-donating groups can improvet he basicity of Ge II .H owever,t hese simple Ge II compounds have not formally achieved superbasicity (PA > 240 kcal mol À1 ).…”