Hydroxy-Substituted Oligosilane Dendrimers: Controlling the Electronic Properties through Hydrogen Bonding

Exploring Planar-Chiral Amino Siloxides

We present the synthesis, structure, and exemplary reactivity of siloxides with a planar-chiral N,N-dimethylaminomethylferrocene backbone. Several zinc complexes based on the racemic as well as the enantiomerically pure silanol were synthesized in the presence of water and crystallographically characterized, and their behavior in solution was examined. The chiral probe present in this system is a valuable tool for identifying the structure in solution. Furthermore, the zinc siloxides exhibit a comparable reactivity to the corresponding silanols. Therefore, they can be regarded as "masked" silanols, especially when the silanols are preparatively inaccessible.

Oligosilanylsilatranes

Oligosilanes with attached silatranyl units were obtained by reactions of potassium oligosilanides with a silatranyl triflate. Interaction between Si and N atoms was observed in the ²⁹Si NMR spectra (upfield-shifted SiO₃ resonances) and in the solid-state structures (Si-N distances between 2.29 and 2.16 Å). The Si-N interaction can be "switched off" either by protonation of the nitrogen lone pair or by potassium silanide formation caused by trimethylsilyl group cleavage in the presence of potassium tert-butoxide.

Heterometallic europium disiloxanediolates: synthesis, structural diversity, and photoluminescence properties

This contribution presents a full account of a structurally diverse class of heterometallic europium disiloxanediolates. The synthetic protocol involves in situ metalation of (HO)SiPh2OSiPh2(OH) (1) with either (n)BuLi or KN(SiMe3)2 followed by treatment with EuCl3 in suitable solvents such as 1,2-dimethoxyethane (DME) or tetrahydrofuran (THF). Reaction of EuCl3 with 2 equiv of (LiO)SiPh2OSiPh2(OLi) in DME afforded the Eu(III) bis(disiloxanediolate) "ate" complex [{(Ph2SiO)2O}2{Li(DME)}3]EuCl2 (2), which upon attempted reduction with Zn gave the tris(disiloxanediolate) [{(Ph2SiO)2O}3{Li(DME)}3]Eu (3). Treatment of EuCl3 with (LiO)SiPh2OSiPh2(OLi) in a molar ratio of 1:2 yielded both the ate complex [{(Ph2SiO)2O}3Li{Li(THF)2}{Li(THF)}]EuCl·Li(THF)3 (4) and the LiCl-free europium(III) complex [{(Ph2SiO)2O}2{Li(THF)2}2]EuCl (5). Compound 5 was found to exhibit a brilliant red triboluminescence. When (KO)SiPh2OSiPh2(OK) was used as starting material in a 3:1 reaction with EuCl3, the Eu(III) tris(disiloxanediolate) [{(Ph2SiO)2O}3{K(DME)}3]Eu (6) was isolated. Attempted ligand transfer between 5 and (DAD(Dipp))2Ba(DME) (DAD(Dipp) = N,N'-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene) afforded the unique mixed-valent Eu(III)/Eu(II) disiloxanediolate cluster [(Ph2SiO)2O]6Eu(II)4Eu(III)2Li4O2Cl2 (7). All new complexes were structurally characterized by X-ray diffraction. Photoluminescence studies were carried out for complex 5 showing an excellent color quality, due to the strong (5)D0→(7)F2 transition, but a weak antenna effect.

Twisted oxygen-containing oligosilanes—unprecedented examples of σ–n mixed conjugated systems

Twisting the silicon backbone conformation in oxygen containing oligosilanes towards dihedral angles of 120-130 degrees either by intramolecular hydrogen bonding or incorporation into a covalently bonded ring system effectively extends the delocalization of electrons in these sigma-n mixed conjugated systems.