A coordination complex, lithium hepta(i-butyl)silsesquioxane trisilanolate (1; Li-T₇), a stable intermediate in silsesquioxane (SQ) syntheses, was successfully isolated in 65% yield and found to be highly soluble in nonpolar solvents such as hexane. The structure of Li-T₇ was confirmed by NMR, IR spectroscopy, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, electrospray ionization mass spectrometry, and computational simulation, providing detailed elucidation of the intermolecular self-association of the SQ cage with a box-shaped Li₆O₆ polyhedron through strong coordination bonds. After acid treatment, Li-T₇ undergoes lithium–proton cationic exchange, yielding hepta(i-butyl)silsesquioxane trisilanol (2; H-T₇) quantitatively. The high yield of H-T₇ seems to be influenced by Li–O bonding in the Li-T₇ complex that affects the selective formation of hepta(i-butyl)silsesquioxane trisilanolate and the bulky i-butyl groups which may prevent decomposition or SQ cage-rearrangement even at reflux under alkaline conditions. Single-crystal X-ray crystallography confirms the presence of the dumbbell-shaped SQ partial cages through strong intermolecular hydrogen bonds. Interestingly, lowering the polarity of the reaction solution by adding dichloromethane results in formation of the cubic octa(i-butyl)silsesquioxane (3; T₈) cage in a good yield (47%), which is isolated by crystallization from the reaction solution.

 Reference

“Lithium Templated Formation of Polyhedral Oligomeric Silsesquioxanes (POSS)” Prigyai, N.; Chanmungkalakul, S.; Ervithayasuporn, V.*; Yodsin, N.; Jungsuttiwong, S.; Takeda, N.; Unno, M.; Boonmak, J.; Kiatkamjornwong, S. Inorg. Chem. 58 (2019) 15110-15117. https://pubs.acs.org/doi/full/10.1021/acs.inorgchem.9b01836