Catalytic Approach to Germanium-Functionalized Silsesquioxanes and Germasilsesquioxanes

Highly selective α-hydrogermylation of alkynes catalyzed by an in situ generated bulky NHC-cobalt complex

A new catalytic system, based on an octacarbonyl dicobalt(0) complex and bulky ligand, providing a route to α-vinylgermanes is described. The proposed method can be effectively used for Markovnikov-selective hydrogermylation of a number of terminal and internal alkynes. It has been proved that analogous catalytic systems containing less sterically demanding ligands cannot serve as selective catalysts in this transformation.

Access to germasiloxanes and alkynylgermanes mediated by earth-abundant species

The reactions between silanols or terminal acetylenes with alkynylgermanes have been accomplished using potassium bis(trimethylsilyl)amide as the catalyst. This strategy has provided an entry point into various organogermanes including germasiloxanes and alkynylgermanes. Remarkably, not only KHMDS but also simple bases such as KOH can serve as efficient catalysts in this process.

New Ceramics Precursors Containing Si and Ge Atoms-Cubic Germasilsesquioxanes-Synthesis, Thermal Decomposition and Spectroscopic Analysis

Compounds of the silsesquioxane type are attractive material precursors. High molecular weights and well-defined structures predestine them to create ceramics with a controlled composition at the molecular level. New molecular precursors of ceramic materials with the ratio of Si:Ge = 7:1 atoms were obtained. The influence of organic substituents on the thermal decomposition processes of germasilsesquioxanes was investigated. Some of the structures obtained are characterized by a high non-volatile residue after the thermal decomposition process. The introduction of the germanium atom to the structure of the silsesquioxane molecular cage reduces the thermal stability of the obtained structures.

Cooperative assembly of redistributed arylgermanium-bearing alkoxysilanes in a mesostructured siloxane network

Three redistributed arylgermanium-bearing mono-, bis- and tris-triethoxysilyl arms were designed, cocondensed with TEOS to access SBA-15-type materials and embedded in chitosan to prepare functional bioplastics.

Assembly of discrete and oligomeric structures of organotin double-decker silsesquioxanes: inherent stability studies

Discrete and oligomeric organotin DDSQs have been synthesized and characterized, both experimentally and through computational study. The stability of these compounds remains intrigued with the organization of their structure in the crystal lattice.

Synthesis of Bifunctional Silsesquioxanes and Spherosilicates with Organogermyl Functionalities

In this paper we present the synthesis of mixed bifunctional compounds of T₈ H₈ silsesquioxane and spherosilicate (HSiMe₂ O)₈ Si₈ O₁₂ derivatives via platinum-catalyzed hydrosilylation of alkenylgermanes and olefins. To the best of our knowledge, this is the first literature example of bifunctional compounds with organogermyl functionalities. Eleven mixed systems with a variety of substituents (Si-H, alkyl, germyl, epoxy, and hydroxy) were prepared and fully characterized by NMR spectroscopy. Additionally, our research includes a real-time FT-IR study of the synthesis of these bifunctional compounds of the general formula (R)_8-m (GeR'₃ (CH₂ )_n+2 R)_m Si₈ O₁₂ . and (R''(CH₂ )₂ R)_8-m (GeR'₃ (CH₂ )₂ R)_m Si₈ O₁₂ where m∼4.

B(C6F5)3-Catalyzed Dehydrocoupling of POSS Silanols with Hydrosilanes: A Metal-Free Strategy for Effecting Functionalization of Silsesquioxanes

We report a highly effective metal-free catalytic procedure for the functionalization of silsesquioxanes via dehydrocoupling of various POSS silanols with hydrosilanes in the presence of commercially available tris(pentafluorophenyl)borane B(C₆F₅)₃. This approach enables the unprecedented one-pot synthesis of valuable silsesquioxane derivatives under mild conditions, with no corrosive byproducts formed in the process.

Synthesis and Hydrosilylation of Vinyl-Substituted Open-Cage Silsesquioxanes with Phenylsilanes: Regioselective Synthesis of Trifunctional Silsesquioxanes

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.

The first example of a fully specified synthetic protocol allowing selective modification of trivinyl-substituted open-cage silsesquioxanes with silanes via platinum-catalyzed hydrosilylation is presented.

Dialkenylgermanes as Precursors of Silsesquioxane-based Macromolecular Structures

Herein we report a study of highly efficient platinum-catalyzed hydrosilylation of dialkenylgermanes with silsesquioxanes and spherosilicates. The use of divinyl- and diallylgermanes allowed the synthesis of new classes of compounds, i. e., dumbbell-type systems, silsesquioxanes with alkenyl pendant group, and oligomeric derivatives. The results are supported by detailed data from in situ FT-IR and NMR measurements, enabling precise monitoring of the reaction progress and determination of regioselectivity of the formed products.

Introduction of organogermyl functionalities to cage silsesquioxanes

In this work, we present the first example of highly efficient platinum-catalyzed hydrosilylation of vinyl- and allylgermanes with different types of silsesquioxanes and spherosilicates. This protocol allows the straightforward introduction of organogermyl functionalities with alkyl chains linked to the silsesquioxane core with good yields and excellent selectivity. These derivatives may be applied as precursors for the development of advanced hybrid materials in the future. In addition, a comparison made between vinylsilanes and vinylgermanes showed a higher reactivity of germanium compounds in the hydrosilylation reaction. To the best of our knowledge, this is the first literature example of the functionalization of silsesquioxanes and spherosilicates with these types of germanium derivatives. The reaction parameters and kinetics were determined by in situ FT-IR. In addition, our research is supported by extensive data obtained from NMR measurements.

Silylation of silanols with hydrosilanes via main-group catalysis: the synthesis of unsymmetrical siloxanes and hydrosiloxanes

Apart from some specific synthetic solutions, a dehydrogenative coupling of silanols with hydrosilanes seems to be the most atom-economical and practical method for the formation of unsymmetrical siloxanes.

A Highly Effective Route to Si-O-Si Moieties through O-Silylation of Silanols and Polyhedral Oligomeric Silsesquioxane Silanols with Disilazanes

A simple and highly practical catalyst-free O-silylation of silanols with commercially available disilazanes has been developed under mild conditions. In the case of polyhedral oligomeric silsesquioxane (POSS) silanols and some other silanols, it was necessary to use catalytic amounts of inexpensive Bi(OTf)₃ as additional catalyst. This efficient chlorine-free protocol involves the synthesis of a wide range of important organosilicon derivatives such as unsymmetrical disiloxanes and functionalized silsesquioxanes.

Synthesis of (E)-1,4-disilsesquioxylsubstituted but-1-en-3-ynes via platinum-catalyzed dimerization of ethynylsiloxysilsesquioxanes

A new platinum complex bearing bulky N-heterocyclic carbene ligand of the general formula [Pt(IPr*Ph)(dvtms)] (where IPr*Ph = 1,3-bis{2,4,6-tris(diphenylmethyl)phenyl}imidazol-2-ylidene, dvtms = divinyltetramethyldisiloxane) exhibits a high catalytic activity towards E-selective dimerization of ethynyl substituted siloxysilsesquioxanes. This process leads to a novel class of functionalized silsesquioxane derivatives, resembling their dumbbell-shaped silsesquioxane analogues.

Copper(ii) triflate-mediated synthesis of functionalized silsesquioxanes via dehydrogenative coupling of POSS silanols with hydrosilanes

In light of the fact that the design of new catalytic routes leading to functionalized silsesquioxanes is currently of high relevance; herein we report a novel, highly effective and convenient catalytic approach for the modification of silsesquioxanes. We present a dehydrogenative coupling reaction of completely as well as incompletely condensed POSS silanols with a wide range of commercially available hydrosilanes mediated by inexpensive copper(ii) trifluoromethanesulfonate. This research also includes mechanistic studies for this process.

Introduction of Boron Functionalities into Silsesquioxanes: Novel Independent Methodologies

Owing to their versatile application possibilities, silsesquioxanes (SQs) are of considerable interest for creating hybrid inorganic-organic materials. In this report, two novel and independent strategies for the direct attachment of boron functionalities to silsesquioxanes are presented. Encouraged by our previous work concerning the synthesis of borasiloxanes through the catalyst-free dehydrogenative coupling of silanols and boranes, we decided to apply our method to a synthesis of various boron-functionalized silsesquioxanes. During our tests, we also investigated the activity of scandium(III) triflate, which we have previously used as an excellent catalyst for the obtaining of Si-O-Si and Si-O-Ge moieties. As a result, we also discovered a novel approach for the O-borylation of Si-OH groups in silsesquioxanes with allylborane. Both routes are highly chemoselective and efficiently lead to the obtaining of Si-O-B moiety under air atmosphere and at room temperature.

A new “bicycle helmet”-like copper(ii),sodiumphenylsilsesquioxane. Synthesis, structure and catalytic activity

Use of silsesquioxane and 2,2′-bipyridine leads to isolation of catalytically active “Bicycle Helmet” cage.

N-Heterocyclic carbene-based ruthenium-hydride catalysts for the synthesis of unsymmetrically functionalized double-decker silsesquioxanes

The [RuHCl(CO)(SIDip)(PCy₃)] complex efficiently catalyzes the (E)-selective silylative coupling of divinyl-substituted double-decker silsesquioxanes with two distinctly substituted styrenes.

Chemoselective and Catalyst-Free O-Borylation of Silanols: A Facile Access to Borasiloxanes

This paper demonstrates the first highly chemoselective syntheses of various borasiloxanes from hydroboranes and silanols, achieved through catalyst-free dehydrogenative coupling at room temperature. This green protocol, which uses easily accessible reagents, allows for the obtaining of borasiloxanes under air atmosphere and solvent-free conditions.