Unexpected Silaazetidine Formation in the Thermolysis of thf‐Supported Silanimine Et2Si=N–SitBu3·thf

The silyl amide Et₂SiCl‐NLi‐SitBu₃ can be cleanly prepared from precursor silylamine Et₂SiCl‐NH‐SitBu₃ and Li[nBu]. The CF₃SO₃SiMe₃ induced LiCl elimination of Et₂SiCl‐NLi‐SitBu₃ in thf afforded a 2‐silaazetidine derivative by [2+2] cycloaddition of Et₂Si=N–SitBu₃ with Et₂Si(OCH=CH₂)–NH–SitBu₃. X‐ray quality crystals of this 2‐silaazetidine derivative (triclinic, space group P$\bar{1}$ ) were grown from benzene at room temperature. The starting material for this approach, Et₂SiCl–NH–SitBu₃, is water‐sensitive. Hydrolysis of Et₂SiCl‐NH‐SitBu₃ gave [tBu₃SiNH₃]Cl along with (Et₂SiO)_n oligomers. The hydro chloride [tBu₃SiNH₃]Cl could be isolated and was characterized by X‐ray crystallography (trigonal, space group P$\bar{3}$ ).     

Disupersilylperoxo Radical Anion [tBu3SiOOSitBu3]⋅−: An Intermediate of Supersilanide Oxidation

In the oxidative process of the supersilanide anion [SitBu₃]^?, radical species are generated. The continuous wave (cw)‐EPR spectrum of the reaction solution of Na[SitBu₃] with O₂ revealed a signal, which could be characterized as disupersilylperoxo radical anion [tBu₃SiOOSitBu₃]^?? affected by sodium ions though ion‐pair formation. A mechanism is suggested for the oxidative process of supersilanide, which in a further step can be helpful in a better understanding of the oxidation process of isoelectronic phosphanes.     

Enantioselektive Katalysen. 155 [1] (Cymol)Ruthenium‐Halbsandwich‐Komplexe mit Pyrroloxazolin‐Liganden — Synthese,Stereochemie, Katalyse

Asymmetric Catalysis. 155 [1] (Cymene)Ruthenium Halfsandwich Complexes with Pyrroleoxazoline Ligands — Synthesis, Stereochemistry, Catalysis The (cymene)ruthenium halfsandwich complexes K1 and K2 with chiral pyrroleoxazoline ligands were synthesized and characterized. The complexes form diastereomers, which only differ in the metal configuration. Complex K1 crystallized as the pure diastereomer S_Ru, S_C4, R_C5. In solution epimerization S_Ru, S_C4, R_C5 ? R_Ru, S_C4, R_C5 occurred via change of the configuration at the ruthenium atom. The half‐life for the first‐order reaction at 0.4 °C in CD₂Cl₂ was 50.6 min. Thus, the two diastereomers equilibrate at room temperature. The equilibrium mixtures of K1 und K2 were used as catalysts for the transfer hydrogenation of acetophenone and for the Diels‐Alder reaction of cyclopentadiene with methacrolein. Enantiomeric excesses of up to 60 % ee were achieved.