Synthese eines funktionalen Aluminiumalkinids, Me₃C‐C≡C‐AlBr₂, und dessen Reaktionen mit der sperrigen Lithiumverbindung LiCH(SiMe₃)₂

Abstract

Synthesis of a Functional Aluminium Alkynide, Me3C‐C≡C‐AlBr2, and its Reactions with the Bulky Lithium Compound LiCH(SiMe3)2Treatment of aluminium tribromide with the lithium alkynide (Li)C≡C‐CMe3 afforded the aluminium alkynide Me3C‐C≡C‐AlBr2 (1) in an almost quantitative yield. 1 crystallizes with trimeric formula units possessing Al3C3 heterocycles and the anionic carbon atoms of the alkynido groups in the bridging positions. A dynamic equilibrium was determined in solution which probably comprises trimeric and dimeric formula units. Reaction of 1 with one equivalent of LiCH(SiMe3)2 yielded the compound [Me3C‐C≡C‐Al(Br)‐CH(SiMe3)2]2 (2), which is a dimer via Al‐C‐Al bridges. Two equivalents of the lithium compound gave a mixture of four main‐products, which could be identified as 2, Li[Me3C‐C≡C‐Al{CH(SiMe3)2}3] (3), Me3C‐C≡C‐Al[CH(SiMe3)2]2 (4), and Al[CH(SiMe3)2]3. The lithium atom of 3 is coordinated by the C≡C triple bond and an inner carbon atom of one bis(trimethylsilyl)methyl group. Further interactions were observed to C‐H bonds of methyl groups.

Diphenylacetylene stabilised alkali-metal nickelates: synthesis, structure and catalytic applications

“…Li3⋯C4 distances [2.446(4) Å and 2.563(3) Å, respectively]. Anagostic interactions between CH 3 groups and Li have been observed in several crystal structures, 37,38 including in lithium nickelates, 39 but this is limited to intramolecular examples. In addition, there is considerable torsion in the diphenylacetylene unit [C5-C6-C7-C8 = 20.1(3)°, see Table 1 for general label numbering] to enable additional C arene ⋯Li2 interactions [2.727(4)-2.750(4) Å].…”

Alkynes Between Main Group Elements: From Dumbbells via Rods to Squares and Tubes

“…In Figure 9, we have depicted ten dimers. The formulas were drawn according to the results of X-ray investigations (106 and 108-115) [91][92][93][94][95][96] or electron diffraction studies (107). 97 It is seen that those dimers with bulky substituents at the metal prefer the D 2h -type structure (112)(113)(114), whereas all others choose the C 2h geometry.…”

Treatment of a Methylene‐Bridged Dialuminium Compound with Lithium Alkanides and Alkynides ‐ Single vs. Twofold Terminal Coordination

“…Interestingly even the methyl group of 2a does not occupy a bridging position between both metal atoms although methyl bridges are well‐known in dimeric trimethylaluminium 15. Similarly, simple aluminium alkynides (R 2 Al‐C≡C‐R') 2 (R = alkyl; R' = aryl, alkyl) with relatively small groups give dimeric16 or trimeric formula units17 with the α‐C atoms of the alkynides in the bridging positions, while monomers were observed even in the solid state only with very bulky substituents [R= CH(SiMe 3 ) 2 ] 18. Steric reasons, electrostatic repulsion between the electropositive aluminium atoms, which in the hydrido species approach to a relatively close contact of 275 pm, and the particular bonding situation in bis(trimethylsilyl)methyl aluminium compounds (see below) may favour the formation of adducts with the alkyl or alkynyl substituents in terminal positions.…”