Acid‐Base Interactions of Pyrazine, Ethyl Acetate, Di‐alcohols, and Lysine with the cyclic Alumosiloxane (Ph2SiO)8[Al(O)OH]4 in View of Mimicking Al2O3(H2O) Surface Reactions

Abstract

The etherate of (Ph2SiO)8[Al(O)OH]4 can be transformed into the pyrazine adduct (Ph2SiO)8[Al(O)OH]4·3N(C2H2)2N (1), the ethyl acetate adduct (Ph2SiO)8[Al(O)OH]4·3H3C‐C(O)OC2H5 (2), the 1,6‐hexane diol adduct (Ph2SiO)8[Al(O)OH]4·2HO–CH2(CH2)4CH2–OH (3) and the 1,4‐cyclohexane diol adduct (Ph2SiO)8[Al(O)OH]4·4HO–CH(CH2CH2)2CH–OH (4). In all compounds the OH groups of the starting material bind to the bases through O–H···N (1) or O–H···O hydrogen bonds (2, 3, 4) as found from single‐crystal X‐ray diffraction analyses. Whereas in 1 only three of the central OH groups bind to the pyrazines, in 2 two of them bind to the same carbonyl oxygen atom of the ethyl acetate resulting in an unprecedented O–H···O···H–O double hydrogen bridge. The hexane diol adduct 3 in the crystal forms a one‐dimensional coordination polymer with an intramolecularly to two OH groups grafted hexane diol loop, while the second hexane diol is connecting intermolecularly. In the cyclohexane diol adduct 4 all OH groups of the central Al4(OH)4 ring bind to different diols, leaving one alcohol group per diol uncoordinated. These “free” OH groups form an (O‐H···)4 assembly creating a three‐dimensional overall structure. When reacting with (Ph2SiO)8[Al(O)OH]4 lysine loses water, turns into the cyclic 3‐amino‐2‐azepanone, and transforms through chelation of one of the aluminum atoms the starting material into a new polycycle. The isolated compound has the composition (Ph2SiO)12[Al(O)OH]4[Al2O3]2·4 C6H12N2O·6(CH2)4O (5).