Die Kristall- und Molekülstruktur von Bis(trimethylsilyldiimin)

Abstract

The crystal structure of bis(trimethylsilyl)diimine, (CH3)3Si-N=N-Si(CH3)3, has been determined from three-dimensional X-ray data collected on a Stoe two-circle diffractometer at -130°C (Mo K(alpha) radiation, 673 reflexions, R=0·067). The crystals are monoclinic, space group P2(1/c), with cell dimensions a=6·12 (2), b=10·788 (3), c=8·892 (3) Å, and ß=103·4 (1)°. There are only two molecules in the unit cell and, consequently, the crystal site symmetry must be 1¯ (Ci). For several reasons, however, the free molecule is to be expected to adopt the higher point symmetry 2/m (C2h). Important molecular dimensions are the very short N-N bond (1·17 Å), the unusual long Si-N bond (1·81 Å), and the Si-N-N angle of 120°, which indicate the exceptional position of this compound among the other known trans-X-N=N-X systems. It is shown that some geometrical details of the crystal and molecular structure result from the stereochemical activity of the nitrogen lone pair.