Synthesis and characterization of tin containing polyhedral oligometallasilsesquioxanes (POMSS)

Abstract

Tin silicate species have shown good catalytic activity in various oxidation reactions. In an attempt to mimic surface tin species, several tin containing silsesquioxanes have been synthesized. Incompletely condensed silsesquioxanes (c-C5H9)7Si7O9(OH)3 and (c-C5H9)7Si7O9(OSiMe3)(OH)2 were reacted with common tin-precursors, which afforded several silsesquioxane ligated tin compounds. Divalent stannasilsesquioxanes form dimers of the type [(c-C5H9)7Si7O11(OX)Sn]2(X=H, SiMe3) with three-coordinated tin centers. The three-coordinated tin(II) are hydrolytically unstable whereas the octahedrally surrounded tetravalent stannasilsesquioxanes [(c-C5H9)7Si7O11(OX)]Sn(acac)2(X=H, OSiMe3) are hydrolytically robust. An unprecedented anionic trimeric cluster, [[(c-C5H9)7Si7O12Sn]3(mu2-OH)3(mu3-OH)]-[HNEt3]+, stabilized by bridging hydroxyl groups was formed when the product formed upon reacting (c-C5H9)7Si7O9(OH)3 with SnCl4 was slowly hydrolyzed. The stannasilsesquioxanes showed no catalytic activity in oxidation reactions.

Tin Silsesquioxanes as Models for the “Open” Site in Tin‐Containing Zeolite Beta

“…These octahedral tin(IV) structures are stable in the presence of small amounts of water. [15] Figure 1. Schematic representation of the hypothesized active sitespresent in Sn-Betaa nd the analogous tin silsesquioxanes synthesized.…”

Modern concepts and methods in the chemistry of polyhedral metallasiloxanes

“…When one of the Si-OH groups is blocked by OЕR х fragments (Е denotes non-metal), several unusual metal-containing compounds can be obtained based on modified cubane synthones ( Fig. 5; 9, R = c-C 5 H 9, [44]; 10, R = c-C 5 H 9 , [42]; 11, R = c-C 5 H 9 , X =, B(C 6 F 5 ) 2 [45], X = SiMeVin 2 [46]; 12, R = c-C 5 H 9, X = Me 3 , MePh 2 [47]; 13, R = c-C 6 H 11 , [48]; 14, R = c-C 5 H 9 , [49]; 15, R = c-C 6 H 11 , [35] [44] 10 [42] 11 [45] 12 [47] A c c e p t e d M a n u s c r i p t 7 13 [48] 14 [49] 15 [35] This synthetic approach was developed by using a method to obtain an "open" siloxane cage with two Si-OH-groups instead of three. Compound 16 was synthesized in three steps starting with acidic splitting of the closed cubic structure (Scheme 3) [50].…”

“…An important structural feature of these compounds is a central cavity, which can accommodate a small inorganic anion ( Fig. 4; 7 R = c-C 6 H 11 [42]; 8 R = i-Bu, [43]). M a n u s c r i p t Fig.…”

Tetrahedral Sn–silsesquioxane: synthesis, characterization and catalysis

“…8 To be a realistic structural analogue of an active site in zeolite, the metal center of the metallasilsesquioxane should be tetrahedrally coordinated with three of the four ligands being siloxy bonds, and the fourth either a siloxy or an ancillary ligand that can be easily displaced during reaction. Synthesis starting with SnCl 4 were reported to be unsuccessful, 15 even though well-defined T d metallasilsesquioxanes could be formed from TiCl 4 and ZrCl 4 under similar conditions. 14 This could be due to the difficulties in synthesizing tetrahedral (T d ) stannasilsesquioxane.…”