Abstract
Herein, we report an efficient synthesis and functionalization of trifunctional open-cage-type silsesquioxanes. The method proposed has been successfully applied for the synthesis of a library of incompletely condensed silsesquioxanes with vinyldiorganosilyl functional groups, which allows further modification. Detailed studies of hydrosilylation of sterically different open-cage vinylsilsesquioxanes with a wide spectrum of phenylsilanes catalyzed by platinum and rhodium compounds are also reported. The influence of the reaction parameters, types of reagents, and catalysts employed on the efficiency of the process was examined. Optimization of the process based on the above results permitted the design of a very attractive method for the synthesis of multifunctionalized silsesquioxanes with excellent yields and regioselectivity. Moreover, the results allowed the choice of the most efficient catalyst whose application led to the selective formation of substituted open-cage silsesquioxanes. These new compounds have been fully characterized and studied in terms of their thermal properties.
Highlights
Silsesquioxanes make up a group of organosilicon macromolecular cage compounds differing in the number and manner of combination of T units [the basic building blocks consist of one silicon atom covalently linked to three oxygen atoms (Figure 1)]
Polyhedral oligomeric silsesquioxanes (POSSs) are characterized by structural diversity and the possibility of attachment of a variety of functional groups that significantly change their reactivity and solubility.[1−4] These properties can be modified by the introduction of various substituents by using a wide spectrum of catalytic and noncatalytic chemical reactions (e.g., Heck coupling,[5−9] metathesis,[10−16] silylative coupling,[13−18] and many others1,2)
The progress of the condensation reactions was monitored by Fourier transform infrared (FT-IR) spectroscopy as the disappearance of the signals assigned to the stretching vibrations of the −OH groups present in the silanol substrates and the simultaneous appearance of characteristic absorption bands at 1593 cm−1 attributed to C C bonds from vinyl groups in the formed product (Figure 2)
Summary
Silsesquioxanes make up a group of organosilicon macromolecular cage compounds differing in the number and manner of combination of T units [the basic building blocks consist of one silicon atom covalently linked to three oxygen atoms (Figure 1)]. We chose the hydrosilylation reaction to selectively bond chromophores (in the form of phenylsilanes) to derivatives 1−9, which have three vinyl functional groups protruding from the silsesquioxane cage, enabling their further modification and making them molecular scaffolds for the bonding of chromophores.
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