Synthese und Kristallstruktur von Li₂[(Me₃SiCH₂)₃AlCH₂Al(CH₂SiMe₃)₃] — ein Addukt des Dilithiomethans CH₂Li₂?

Abstract

Synthesis and Crystal Structure of Liz[(Me3SiCHZ)3Al -CH2 -A1(CH2SiMe3),] -a Dilithiomethane Derivative?Reaction of (trimethylsilyl)methyllithium with the methylenebridged aluminium tetrachloride ClzAl -CH2 -AlC12 yields dilithium methylenebis[tris(trimethylsilylmethyl)aluminate] (2) as the only isolable product. All attempts for preparing the tetraalkyl analogue have been unsuccessful, The crystal structure of 2 exhibits a hexacoordinated central carbon atom with short Li ~ C distances. Both lithium atoms and the methylene hydrogens of the A1 -CH2 -A1 unit are almost coplanar. The discussion of the structure and properties leads to the attractive description of 2 as an adduct of tris (trimethylsilylmethy1)

An investigation of catalyst/cocatalyst/support interactions in silica-supported olefin polymerization catalysts based on Cp*TiMe3*

“…Spectra are vertically offset. complexes [67][68][69], and are difficult to observe in solution NMR spectra [70,71] as a consequence of the proximity to two quadrupolar 27 Al nuclei. Such signals are expected to be even more difficult to discern in the solid-state due to the rigidity of the methylene carbon and its low abundance.…”

Homo‐ and Heterodimetallic Geminal Dianions Derived from the Bis(phosphinimine) {Ph2P(NSiMe3)}2CH2 and the Alkali Metals Li, Na, and K

“…To date, these compounds include the sulfone [{PhSO 2 A C H T U N G T R E N N U N G (Me 3 Si)CLi 2 } 6 ·Li 2 O·10 THF], [21] the sulfoximine [{PhA C H T U N G T R E N N U N G (MeN)SO(Ph)CLi 2 } 4 ·Li 2 O·6 THF], [22] the phosphonate [({(MeO) 2 POA C H T U N G T R E N N U N G (Me 3 Si)CLi 2 } 3 ·Me 2 N) 2 -A C H T U N G T R E N N U N G ·(Li·2 TMEDA) 2 ], [23] the phosphiminine [{Me 2 PA C H T U N G T R E N N U N G (NSiMe 3 )-A C H T U N G T R E N N U N G CH} 6 ·A C H T U N G T R E N N U N G {Me 2 (Bu)SiO} 2 ·Li 14 ], [24] and the mixed-metal complex [{(Me 3 SiCH 2 ) 3 Al} 2 ·A C H T U N G T R E N N U N G (H 2 CLi 2 )]. [25] All of these crystallographically characterized complexes contain dilithiated carbanions, and we have been interested for some time in preparing geminal organodimetallic derivatives of the heavier alkali metals. [26] Such complexes are interesting on several fronts.…”

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

“…The molecule has a C 2 axis that passes through the atoms Li2 and C3. With both aluminium atoms now being four‐coordinate there is no possibility for hyperconjugative effects and all Al–C bonds [202.9(2) – 204.9(2) pm] are of comparable lengths and similar to those observed to the four‐coordinate aluminium atoms of the mono‐adducts described above or the related solvent‐free compound Li 2 CH 2 {Al(CH 2 SiMe 3 ) 3 } 2 23. One lithium ion of 4a is coordinated in a chelating manner by two TMEN molecules, the other has two short contacts to the α‐carbon atoms of the two alkynyl substituents [Li2–C301 212.9(2) pm].…”