A Methylene-Bridged Dialuminium Compound as a Chelating Lewis Acid: Complexation of Nitrite and Nitrate Anions by R2Al–CH2–AlR2[R = CH(SiMe3)2]⋆

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.…”

Complementary anion binding by bidentate boron-containing Lewis acids

“…Chloroform-d and dichloromethane-d 2 (both Goss) were degassed and dried over molecular sieves prior to use. 3 were obtained from commercial sources and used as received. (catB) 2 O and S,SPh 2 C 2 H 2 (OH) 2 were prepared by the literature routes [5,6].…”

“…The possibility for stronger methide anion binding by a chelating receptor, for example, has led to the synthesis of a number of bifunctional Lewis acids (featuring various spacer groups) and to their investigation as potential alternatives to B(C 6 F 5 ) 3 as olefin polymerization co-catalysts [2c,2d,2e,2f,2g,2h,2-l,2o]. By contrast, the geometric constraints imposed by a single atom spacer mean that systems of the type X 2 B-E 0 (R) n -BX 2 (E 0 = first row element) are unlikely to bind a monodentate anion in chelating fashion [2d], being more appropriate to the complementary bidentate acid/base binding of anions, such as NO À 3 , AcO À or H 2 PO À 4 [3]. Selective binding of bidentate anions such as carboxylates, RCO À 2 (and related anionic and neutral species such as dihydrogenphosphates, amino acids or aromatic nitro compounds) by hosts featuring an appropriate arrangement of hydrogen bond donors is of considerable relevance to biological systems [4].…”

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

“…3; schematic drawing in Eq. 2) that resembles the related adducts of 1a with NO − 3 [14] and H 3 C-CO − 2 [15]. The reduced strain in the larger ring results in a much larger Al-C-Al angle of 120.18 (9) • .…”

“…The use of sterically less demanding ligands resulted in dismutation reactions with the formation of the mononuclear trialkylaluminium derivatives and a mixture of unknown secondary products [13]. The potential of the above dialuminium compounds to react as chelating Lewis acids in the presence of an auxiliary base (e. g. TMEN) was demonstrated for 1a by the synthesis and characterisation of a range of mono-adducts [Li(base) n ][1a(X)] (X = NO 2 [14], NO 3 [14], N 3 [15], CH 3 CO 2 [15], Me 2 PCHPMe 2 [16]) and [Li(base) n ][1a(R')] (R' = H [17], CH 2 -t-Bu [18], Me [19], n-Bu [19], C≡C-SiMe 3 [19], C≡C-t-Bu [19], C≡C-Ph [19], C≡C-PPh 2 [19]). In the solid state the anions X − are chelated by the two aluminium atoms via two of their heteroatoms thereby forming five-or six-membered heterocycles, while in most cases the R' anions are bound in a terminal fashion to only one aluminium atom.…”