Hydroalumination of Bis(alkynyl)silanes: Generation of Chelating Lewis Acids, Their Application in the Coordination of Chloride Ions and a 1,1‐Carbalumination Reaction

Abstract

Treatment of diphenyl-diethynylsilanes, (H 5 C 6 ) 2 Si(CϵC-RЈ) 2 (RЈ = -C 6 H 5 , -4-Me-C 6 H 4 ), with two equivalents of dialkylaluminium hydrides, R 2 Al-H (R = -CMe 3 , -CH 2 CMe 3 ), afforded the corresponding dialkenylsilanes (3-5) by hydroalumination. The mixed alkenyl-alkynyl compounds resulting from the reduction of only one CϵC triple bond occurred as intermediates. Two of these (1 and 2) were isolated and characterized by crystal structure determinations. They show close interactions of the α-carbon atoms of the ethynyl groups with the coordinatively unsaturated aluminium atoms and a cis arrangement of H and Al atoms across the C=C double bonds. cis/trans Rearrangement took place upon the [a]

Alkenyl‐Alkynylgermanes Functionalised by Lewis Acids: Intramolecular Aluminium– and Gallium–Alkyne Interactions and Potential Ge–C Bond Activation

“…Silacyclobutenes exhibit pronounced photoluminescent properties1 that, compared to silicon‐free organic unsaturated compounds, resulted in a redshift of the fluorescence maxima, an increase of the Stokes' shifts and a decrease in quantum yields. 1,1‐Carbaboration2,3 and 1,1‐carbalumination reactions4 starting with alkynylsilanes proved to be powerful methods for their facile synthesis. These reactions proceeded by means of the insertion of the α‐carbon atom of an alkynyl group into a B–C or Al–C bond and the concomitant formation of a Si–C bond to the β‐carbon atom of the alkyne 4.…”

“…1,1‐Carbaboration2,3 and 1,1‐carbalumination reactions4 starting with alkynylsilanes proved to be powerful methods for their facile synthesis. These reactions proceeded by means of the insertion of the α‐carbon atom of an alkynyl group into a B–C or Al–C bond and the concomitant formation of a Si–C bond to the β‐carbon atom of the alkyne 4. Although 1,1‐carbaboration is a relatively common method for the synthesis of organoboranes,2,3 1,1‐carbalumination has been reported for the first time only recently.…”

“…Although 1,1‐carbaboration is a relatively common method for the synthesis of organoboranes,2,3 1,1‐carbalumination has been reported for the first time only recently. Hydroalumination5 of (H 5 C 6 ) 2 Si(C≡C–C 6 H 5 ) 2 with H–Al(CMe 3 ) 2 afforded a mixed alkenyl‐alkynylsilane ( 1 ) (Scheme ), which in toluene at reflux slowly rearranged to yield silacyclobutene 2 4. Compound 2 was isolated as a THF adduct and had an unsaturated SiC 3 heterocycle with conjugated endocyclic and exocyclic C=C bonds and a dialkylaluminium group bonded to one of its ring carbon atoms (Scheme ).…”

The Methylene-bridged Dialuminium Compound R2Al-CH2-AlR2 [R=CH(SiMe3)2] as an Effective Chelating Lewis Acid – Adducts with Halides, Perchlorate and Isopropylamide

“…The solid-state structure revealed a unique molecular arrangement with one of the two lithium cations being sandwiched between two alkynide groups and showing close Li-C contacts to the ethynyl α-C atoms and the bridging CH 2 group. Similar chelating Lewis acids have been obtained by the dual hydrogallation of an alkyne [21,22] or the hydroalumination of silicon-or germanium-centered bis-alkynes [23,24]. In the latter case the acceptor atoms are separated by three bridging atoms (SiC 2 or GeC 2 ).…”

σ‐Bond Activation in Aluminium‐Functionalized Alkynylchlorogermanes: Facile Insertion of Isocyanate and Azide into Al–C and Ge–Cl Bonds

“…We intend to activate bonds of Si or Ge atoms to donor groups by utilising intramolecular coordination of the Lewis bases to Lewis‐acidic Al or Ga atoms in order to allow insertion or rearrangement reactions or the generation of silyl or germyl cations. Suitable compounds for such processes were obtained by hydroalumination or ‐gallation of donor‐functionalized alkynylsilanes and ‐germanes . The resulting alkenyl derivatives featured a geminal arrangement of Al/Ga and Si/Ge atoms at their C–C double bonds.…”