Wagner–Meerwein-Type Rearrangements of Germapolysilanes - A Stable Ion Study

Abstract

The rearrangement of tris(trimethylsilyl)silyltrimethylgermane 1 to give tetrakis(trimethylsilyl)germane 2 was investigated as a typical example for Lewis acid catalyzed Wagner–Meerwein-type rearrangements of polysilanes and polygermasilanes. Direct 29Si NMR spectroscopic evidence is provided for several cationic intermediates during the reaction. The identity of these species was verified by independent synthesis and NMR characterization, and their transformation was followed by NMR spectroscopy.

Cationic Si−H−Si Bridges in Polysilanes: Their Detection and Targeted Formation in Stable Ion Studies

“…Related 1,3‐methyl migrations are important steps in skeletal rearrangement processes of polysilanyl cations and in inter‐ and intramolecular substituent exchange reactions in silylium ions . Recently, we disclosed a similar rearrangement of the closely related silyl cation 11 …”

“…Exploratory investigations by Lambert and Zhang revealed the thermolability of even such small representatives as tris(trimethylsilyl)silylium, (Me 3 Si) 3 Si + . Subsequently, Sekiguchi and co‐workers demonstrated the tendency of dialkyl‐oligosilyl cations to undergo 1,2‐methyl shifts and our group reported recently on the involvement of polysilanylsilyl or germapolysilanylsilyl cations as intermediates in sila‐Wagner–Meerwein rearrangements of polysilanes and germapolysilanes . Common to all the studied polysilanyl compounds is their high reactivity, their thermolability, unusual for silyl cations, and their pronounced tendency to undergo skeletal rearrangement reactions.…”

Tris(trichlorosilyl)tetrelide Anions and a Comparative Study of Their Donor Qualities

“…We rather envisage am ore complex scenarioi nvolvingo ligomerso f( Cl 3 Si) 2 Ge=SiCl 2 and their subsequent rearrangementt oa fford 5.Ap ropensity of the Ge atom to occupy the central position of Si/Ge neo-structures is obvious from the AlCl 3 -catalyzed rearrangemento f( Me 3 Si) 3 Si(GeMe 3 )t og ive (Me 3 Si) 4 Ge. [40] Quantitative Cl/H exchange to furnish (H 3 Si) 4 sulting mixture GeH n (SiH 3 ) 4Àn (n = 0-2) by fractionating condensation and subsequentp reparative gas chromatography. [2] Our new three-stepp rocess GeCl 4 !…”

Dispersion-Energy-Driven Wagner–Meerwein Rearrangements in Oligosilanes

“…23 − 27 Recently, we have been able to document the activity of carbocations, such as the trityl cation, in these catalytic rearrangement reactions. 28 Furthermore, the use of a trityl cation paired with a weakly coordinating anion in stoichiometric amounts allowed the detection of oligosilanylsilyl cations under carefully controlled reaction conditions. 28 , 29 The most prominent example for this type of Lewis acid catalyzed sila-Wagner–Meerwein rearrangement is the synthesis of persilaadamantane 1 from a bicyclic precursor that was reported recently by two of us ( Scheme 1 ).…”

“… 28 Furthermore, the use of a trityl cation paired with a weakly coordinating anion in stoichiometric amounts allowed the detection of oligosilanylsilyl cations under carefully controlled reaction conditions. 28 , 29 The most prominent example for this type of Lewis acid catalyzed sila-Wagner–Meerwein rearrangement is the synthesis of persilaadamantane 1 from a bicyclic precursor that was reported recently by two of us ( Scheme 1 ). 30 During this transformation, the complexity of the bicyclic compound increases significantly by increasing the number of tetrasila-substituted silicon atoms.…”