Abstract Tri-tert-butylsiloxane compounds of transition metals are obtained by two different routes, one of these involves condensation of tri-tert-butylsilanol with the binary oxides V2O5, CrO3, MoO3, and Re2O7, while the other proceeds via a similar reaction between the chlorides VOCl3, NbCl5, TaCl5, CrO2Cl2, and the silanol. The new compounds, having good thermal stability and remarkable resistence to hydrolysis, are characterized by IR, 1H NMR, and mass spectra.

Rotationshinderungen sterischer Art gibt es auch bei Si–C‐Einfachbindungen. Diese bisher nicht beobachtete Erscheinung ließ sich jetzt bei Verbindungen vom Typ (1) nachweisen, in denen das Siliciumatom drei tert.‐Butylgruppen und ein Halogenatom trägt.

1 ) Oxidative addition according to Eq. (I), for example with X = CHzC1, Y =C1. The hypothetical intermediate ( 5 )

angles between Te atoms are similar to those in elemental tellurium. The shortest atom separations between neighboring building units are 3.4 A.Structure analyses for the isotypic halides Te,X were carried out with Te,Br and TeJ. 748 reflections for the bromide (6,,,=25") and 1255 reflections for the iodide

Hexachlordisilan und Trichlor‐trichlormethylsilan reagieren mit Diazomethan ausschließlich unter Methyleninsertion in die Si‐Halogen‐Bindung (Bildung von Chlormethyl‐Derivaten).