Structures of [(Amino)phenylsilyl]lithiums and Related Compounds in Solution and in the Solid State

The solution structures of [bis(diethylamino)phenylsilyl]lithium (1), [(diethylamino)diphenylsilyl]lithium (2), and [(diethylamino)phenylmethylsilyl]lithium (3) were investigated by 13C, 29Si, 7Li, and 15N NMR spectroscopic experiments. The 29Si−7(6)Li coupling can be observed in each species at low temperature. The coupling patterns indicate that these three species exist as monomers in THF. Using a 15N-enrichment technique, the 29Si−15N couplings in 1 and 2 are observed. Next, the solid-state structures of [(diphenylamino)diphenylsilyl]lithium ((Ph2N)Ph2Si−X; X = Li) (4) and its fluoro (X = F) (16), stannyl (X = SnMe3) (17), and hydro (X = H) (18) derivatives were revealed by crystallographic studies as well as by solid-state 29Si NMR experiments. In the solid state, 4 exists as a monomer solvated with three THF molecules arising from the reaction solvent. The electropositive substituent X, such as lithium, causes the elongation of the Si−C and Si−N bonds, reduction of the sum of the C−Si−N (or C) angles, and a downfield shift of the 29Si resonances

Effect of Countercation Inclusion by [2.2.2]Cryptand upon Stabilization of Potassium Organofluorosilicates

The reaction of a series of organofluorosilanes with KF in the presence of [2.2.2]cryptand affords the corresponding organofluorosilicates with K+/[2.2.2]cryptand as the countercation. Not only diorganotrifluorosilicates, Ph2SiF3-, but also triorganodifluorosilicates, Ph3SiF2- and Ph2MeSiF2-, are obtained as stable solids. The X-ray crystal structure analyses of these silicates show that three-dimensional inclusion of the potassium cation by cryptand prevents an interaction between the potassium atom and fluorine atoms of the silicates. A comparison of the countercation between K+/[2.2.2]cryptand and K+/18-crown-6 reveals that the inclusion of the potassium cation by cryptand subtly facilitates the intramolecular ligand exchange, as observed by the variable-temperature 19F NMR spectra

Synthesis and Structures of Tris[2-(dimethylamino)phenyl]silane and -germane Compounds

Tris[2-(dimethylamino)phenyl]silane and -germane compounds (1 and 2) were synthesized and characterized by X-ray crystallography. Three 2-(dimethylamino)phenyl groups in the hydrosilane (1a) and hydrogermane (1b) encapsulate the hydrogen atom bonded to silicon and germanium, which results in the short Si−H and Ge−H bonds and an increase in the s character of the bonds. The silanol (2a) and germanol (2b) exist as monomers through the intramolecular hydrogen bonding between the hydroxy group and one of the amino groups

<i>a</i><i>ll-anti</i>-Octasilane: Conformation Control of Silicon Chains Using the Bicyclic Trisilane as a Building Block

The perfect all-anti-octasilane composed of two bicyclic trisilane units with trimethylsilyl groups at the termini has been synthesized. Its X-ray crystal structure and spectroscopic data demonstrate the effective σ-delocalization over the silicon framework, which is a definitive difference from the unconstrained n-Si8Me18

Tridurylboranes Extended by Three Arylethynyl Groups as a New Family of Boron-Based π-Electron Systems

A series of tris(phenylethynylduryl)boranes (R-C6H4-C⋮C-duryl)3B with various substituents R have been prepared as air-stable solids owing to the steric protection of the boron atom by the three bulky duryl groups. These compounds show unique photophysical properties due to the pπ−π* conjugation through the p-orbital on the boron atom. In particular, a push−pull type derivative with R = NMe2 exhibits a significant solvatochromism of fluorescence from blue to orange colors

Colorimetric Fluoride Ion Sensing by Boron-Containing π-Electron Systems

The boron-containing π-conjugated systems, including tri(9-anthryl)borane (1) and tris[(10-dimesitylboryl)-9-anthryl]borane (2), have been investigated as a new type of fluoride chemosensor. Upon complexation of 1 with a fluoride ion, a significant color change from orange to colorless was observed and, in the UV−visible absorption spectra, the characteristic band of 1 at 470 nm disappeared and new bands around 360−400 nm assignable to π−π* transitions of the anthryl moieties were observed. This change can be rationalized as a result of the interruption of the π-conjugation extended through the vacant p-orbital of the boron atom by the formation of the corresponding fluoroborate. The binding constant of compound 1 with the fluoride ion was quite high [(2.8 ± 0.3) × 105 M-1], whereas 1 only showed small binding constants with AcO- and OH- of around 103 M-1 and no sensitivity to other halide ions such as Cl-, Br-, and I-, thus demonstrating its selective sensing ability to the fluoride ion. In contrast to the monoboron system 1, compound 2 having four boron atoms showed multistage changes in the absorption spectra by the stepwise complexation with fluoride ions

Synthesis and Structures of Tris[2-(dimethylamino)phenyl]silane and -germane Compounds

Tris[2-(dimethylamino)phenyl]silane and -germane compounds (1 and 2) were synthesized and characterized by X-ray crystallography. Three 2-(dimethylamino)phenyl groups in the hydrosilane (1a) and hydrogermane (1b) encapsulate the hydrogen atom bonded to silicon and germanium, which results in the short Si−H and Ge−H bonds and an increase in the s character of the bonds. The silanol (2a) and germanol (2b) exist as monomers through the intramolecular hydrogen bonding between the hydroxy group and one of the amino groups

The Sila-Wittig Rearrangement

The Sila-Wittig Rearrangemen

Photophysical Properties Changes Caused by Hypercoordination of Organosilicon Compounds: From Trianthrylfluorosilane to Trianthryldifluorosilicate

Photophysical Properties Changes Caused by Hypercoordination of Organosilicon Compounds:  From Trianthrylfluorosilane to Trianthryldifluorosilicat

Silole Polymer and Cyclic Hexamer Catenating through the Ring Silicons

Silole Polymer and Cyclic Hexamer Catenating through the Ring Silicon