Novel route to silanetriols and silanediols based on acetoxysilylalkoxides

Thermally stable polyfluorinated monoalkoxysilanetriols and dialkoxydisiloxanetetrols

The reaction of the polyfluorinated lithium triarylmethanolates Ar₃COLi (Ar = C₆F₅, 3,5-(CF₃)₂C₆H₃) with SiCl₄ provided the monosubstituted products Ar₃COSiCl₃ (1a, Ar = C₆F₅; 1b, Ar = 3,5-(CF₃)₂C₆H₃). The hydrolysis of 1a and 1b produced the silanetriols Ar₃COSi(OH)₃ (2a, Ar = C₆F₅; 2b, Ar = 3,5-(CF₃)₂C₆H₃) without the aid of an HCl scavenger. The reaction of two equivalents of Ar₃COLi (Ar = C₆F₅, 3,5-(CF₃)₂C₆H₃) with (Cl₃Si)₂O afforded the disubstituted products [(C₆F₅)₃COSiCl₂]₂O (3a) and {[(3,5-(CF₃)₂C₆H₃)₃CO]SiCl₂}₂O (3b), the hydrolysis of which gave the corresponding disiloxanetetraols [(C₆F₅)₃COSi(OH)₂]₂O (4a) and [(3,5-(CF₃)₂C₆H₃)₃COSi(OH)₂]₂O (4b). At high concentrations in the presence of HCl, 2b undergoes controlled condensation to yield 4b. In the solid-state, 2a, 4a and 4b are mainly associated by hydrogen bonds of the type SiO-H⋯O(H)Si whereas the competing SiO-H⋯O(C)Si type was not observed.

Hydrosilyation of CO2 using a silatrane hydride: structural characterization of a silyl formate compound

The silatrane hydride compound, [N(CH2CH2O)3]SiH, reacts with CO2 in the presence of the [tris(2-pyridylthio)methyl]zinc hydride complex, [Tptm]ZnH, to afford the silyl formate and methoxide derivatives, [N(CH2CH2O)3]SiO2CH and [N(CH2CH2O)3]SiOCH3. The molecular structure of [N(CH2CH2O)3]SiO2CH has been determined by X-ray diffraction, thereby demonstrating that the formate ligand adopts a distal conformation in which the uncoordinated oxygen atom resides with a trans-like disposition relative to silicon. Density functional theory calculations indicate that the atrane motif of [N(CH2CH2O)3]SiO2CH is flexible, such that the energy of the molecule changes relatively little as the Si···N distance varies over the range 2.0–3.0 Å.

The Influence of Weakly Coordinating Cations on the O-H⋅⋅⋅O- Hydrogen Bond of Silanol-Silanolate Anions

The reaction of a saline phosphazenium hydroxide hydrate with siloxanes led to a novel kind of silanol-silanolate anions. The weakly coordinating behavior of the cation renders the formation of silanol-silanolate hydrogen bonds possible, which otherwise suffer from detrimental silanolate-oxygen cation interactions. We investigated the influence of various weakly coordinating cations on silanol-silanolate motifs, particularly with regard to different cation sizes. While large cations favor the formation of intramolecular hydrogen bonds resulting in cyclic structures, the less bulky tetramethyl ammonium cation encourages the formation of polyanionic silanol-silanolate chains in the solid state.

Bifunctional silanol-based HBD catalysts for CO2 fixation into cyclic carbonates

Unprecedented silanol-based bifunctional HBD catalysts with tetraalkylammonium units directly incorporated into their structures were prepared from tailor-made silanols and used in the preparation of cyclic carbonates.