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 (Ph 2 SiO) 8 [Al(O)OH] 4 can be transformed into the pyrazine adduct (Ph 2 SiO) 8 [Al(O)OH] 4 •3N(C 2 H 2) 2 N (1), the ethyl acetate adduct (Ph 2 SiO) 8 [Al(O)OH] 4 •3H 3 C-C(O)OC 2 H 5 (2), the 1,6-hexane diol adduct (Ph 2 SiO) 8 [Al(O)OH] 4 •2HO-CH 2 (CH 2) 4 CH 2-OH (3) and the 1,4-cyclohexane diol adduct (Ph 2 SiO) 8 [Al(O) OH] 4 •4HO-CH(CH 2 CH 2) 2 CH-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 Xray 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

Zn(II)–Siloxane Clusters as Versatile Building Blocks for Carboxylate-Based Metal–Organic Frameworks

“…Finally, establishing synthetic conditions for cyclic siloxanes of different nuclearities in the SBU would be truly impactful for future developments of SiMOFs. The occurrence of a tetrameric cycle is quite common in the literature, probably because of its thermodynamic stability. , However, there are abundant examples of other types of metal–siloxane clusters in the literature, − and thus, the synthetic strategy used in this work could be a useful guide for such efforts.…”

“…The presence of metal ions in organosilicate materials would be advantageous in view of both structural and functional aspects. Therefore, it is not surprising that molecular clusters of metal-bound cyclic siloxanes have been reported at least 35 years ago and have been an active area of research since then. − It would be informative to note here that a dominant proportion of these metal–siloxane clusters are of the structural type where transition metal ions are sandwiched between two cyclic siloxanes. − Despite the persistent coordination behavior of cyclic siloxanes toward s-, d-, and f-block metal ions, − this area of research has not seen extended solids based on these promising building blocks. This realization naturally leads to the question as to whether the structural chemistry of metal–siloxane can reach beyond the molecular level, which is 0-dimension (0D).…”

Transformations of the polycyclic Alumosiloxane Al2(OSiPh2OSiPh2O)3 into new Polycycles and Co(II) and In(III) derivatives of (Ph2SiO)8[Al(O)OH]4

“…[12,13,14] Because of its defined OÀ Al(OH)À O substructure I may also be used to mimic aluminum hydroxide surface reactivity as recently shown with the amino acid lysine. [15] Finally, this pentacyclic I as well as the bicyclic Al 2 (OSiPh 2 OSiPh 2 O) 3 • 2Q (II) [16] (see Figure 1), which can only be generated under strict exclusion of water and air, react with small amounts of water to form a multitude of polycyclic molecules which even incorporate complex building blocks like [Al 2 (OH) 8 ] 2À . [17] Intrigued by the transformations of the polycycles I and II into complex structures we had a closer look on the formation of cyclic compounds during hydrolysis and condensation of I and II.…”