Issue 14, 2016

Functionalized alkynyl-chlorogermanes: hydrometallation, Ge–Cl bond activation, Ge–H bond formation and chlorine-tert-butyl exchange via a transient germyl cation

Abstract

Treatment of alkynyl–arylchlorogermanes ArylnGe(Cl)(C[triple bond, length as m-dash]C–tBu)3−n (n = 1, 2) with HMtBu2 (M = Al, Ga) yielded mixed Al or Ga alkenyl–alkynylchlorogermanes via hydrometallation reactions. Intramolecular interactions between the Lewis-basic Cl atoms and the Lewis-acidic Al or Ga atoms afforded MCGeCl heterocycles. The endocyclic M–Cl distances were significantly lengthened compared to the starting compounds and indicated Ge–Cl bond activation. Dual hydrometallation succeeded only with HGatBu2. One Ga atom of the product was involved in a Ga–Cl bond, while the second one had an interaction to a C–H bond of a phenyl group. In two cases treatment of chlorogermanes with two equivalents of HAltBu2 resulted in hydroalumination of one alkynyl group and formation of unprecedented Ge–H functionalized germanes, Aryl–Ge(H)(C[triple bond, length as m-dash]C–tBu)[C(AltBu2)[double bond, length as m-dash]C(H)–tBu] (Aryl = mesityl, triisopropylphenyl). The Al atoms of these compounds interacted with the α-C atoms of the alkynyl groups. Ph(Cl)Ge(C[triple bond, length as m-dash]C–tBu)[C(AltBu2}[double bond, length as m-dash]C(H)–tBu] reacted in an unusual Cl/tBu exchange to yield the tert-butylgermane Ph(tBu)Ge(C[triple bond, length as m-dash]C–tBu)[C{Al(tBu)(Cl)}[double bond, length as m-dash]C(H)–tBu]. Quantum chemical calculations suggested the formation of a germyl cation as a transient intermediate.

Graphical abstract: Functionalized alkynyl-chlorogermanes: hydrometallation, Ge–Cl bond activation, Ge–H bond formation and chlorine-tert-butyl exchange via a transient germyl cation

Supplementary files

Article information

Article type
Paper
Submitted
07 oct. 2015
Accepted
19 nov. 2015
First published
19 nov. 2015

Dalton Trans., 2016,45, 6159-6174

Functionalized alkynyl-chlorogermanes: hydrometallation, Ge–Cl bond activation, Ge–H bond formation and chlorine-tert-butyl exchange via a transient germyl cation

C. Honacker, Z. Qu, J. Tannert, M. Layh, A. Hepp, S. Grimme and W. Uhl, Dalton Trans., 2016, 45, 6159 DOI: 10.1039/C5DT03918E

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