From Bidentate Gallium Lewis Acids to Supramolecular Complexes

Abstract

Bidentate gallium Lewis acids were prepared by the reaction of diethynyldiphenylsilane with neat trimethyl- or triethylgallium. Bis[(dimethylgallyl)ethynyl]diphenylsilane (1) and diethylgallyl derivative 2 were characterized as Et O or pyridine adducts by NMR spectroscopy; 2⋅2Py was isolated. Lewis acids 1 and 2 form host-guest adducts with bidentate nitrogen bases, but defined cyclic 1:1 adducts are only formed between 1 and bases with matching N⋅⋅⋅N distances: 4,4'-dimethyl-3,3'-bipyridinylacetylene (3), bis[(pyridin-3-yl)ethynyl]diphenylsilane (4), and bis[(2-methylpyridin-5-yl)ethynyl]diphenylsilane (5). The structures of adducts 1⋅3, 1⋅4, and 1⋅5 were established by X-ray diffraction experiments. 2⋅2Py reacts with DABCO to afford polymeric (DABCO-2-) .

Silicon‐Bridged Bi‐ and Tridentate Lewis Acidic Host Systems

“…[10] Recently, we reported various "pincer-like" PLAs based on diethynyl-or divinyl-diphenylsilanes. [9,10] This simple "backbone" proved to be extremely multifaceted. For example, in complexation experiments with bis-pyridine bases, the rigid gallyl-substituted A1 (Scheme 1) showed a pronounced selectivity with respect to the distance between the Lewis basic sites of the guest compound.…”

“…For example, in complexation experiments with bis-pyridine bases, the rigid gallyl-substituted A1 (Scheme 1) showed a pronounced selectivity with respect to the distance between the Lewis basic sites of the guest compound. [9] Due to the versatility of the silicon core, semiflexible representatives (A2) with comparatively weak Lewis-acidic silyl groups were also described. [10] The fluorinated systems were suitable for complexation of fluoride ions, but owing to the relatively weak Lewis-acidity they showed no complexation ability for neutral guest molecules.…”

Chalice‐Type Tridentate Silicon Lewis Acids of C3 Symmetry in a Single Step Starting from Hexadehydrotribenzo[12]annulene

“…With such directed poly‐Lewis acids we aim to define a cavity that binds a Lewis basic substrate in chelating fashion while the defined distances between the binding functions defines chemical selectivity. For bidentate Lewis acids we used for instance dialkynylanthracenes [15] or diphenyldiethynylsilanes, [16] diphenyldiethenylsilanes as well as diphenyldiethylsilanes [17] to carry two acid functions like B(C 6 F 5 ), AlR 2 , GaR 2 and InR 2 (R=Me, Et). Tris‐Lewis‐acids were realized with trifunctional skeletons including the bowl‐shaped tribenzotriquinacene, [18] tris‐( ortho ‐phenyl)‐silane, [19] 1,8,13‐substituted triptycenes [20] or all‐ cis ‐1,3,5‐triethynyl‐1,3,5‐trisilacyclohexane [21] carrying the Lewis acid groups.…”

Zweizähnige Bor‐Lewis‐Säuren und ihre Selektivität in der Wirt‐Gast‐Komplexbildung

“…minale Alkine einfach funktionalisierbar sind, z. B. mittels Alkan-Eliminierung mit Metallalkylen, [22,23] in Hydrometallierungsreaktionen [24] oder durch Deprotonierung mit nachfolgender Salzelimierung. [6] Während die Wirt-Gast-Chemie der PLS früher hauptsächlich auf die Komplexierung (monoatomarer) anionischer Gäste beschränkt war, [25] gibt es heute auch einige Addukte mit neutralen multidentaten Lewis-Basen.…”

“…Diese Addukte waren in ihren Kristallen mit Rçntgenbeugung nachweisbar. [23] Die Mehrheit bekannter zweizähniger Bor-Lewis-Säuren beruht auf 1,8-substituierten Naphthalin-Gerüsten. [5] Viele davon dienen als Rezeptoren fürk leine Gäste wie Fluoridionen.…”