An X-ray investigation of a so-called disilyl hexamethylcyclotrisilazane. The crystal and molecular structure of a disilyl tetramethylcyclodisilazane

Abstract

Single-crystal X-ray diffraction methods show that a double silylation of hexamethylcyclotrisilazane with ClSiMePh₂ does not give the expected derivative but a cyclodisilazane, 1-methyldiphenylsilyl-3-(1,1,3-trimethyl-3,3-diphenylsilazanyl)-2,2,4,4-tetramethylcyclodisilazane, (III). The disilazane crystals are monoclinic, space group P2₁/c with a= 15·790, b= 8·443, c= 27·944 Å, β= 103·9°. The R factor for 2726 reflections whose intensities were measured on a linear diffractometer is 0·087. The four-membered silicon–nitrogen ring is planar. The Si–C(Me) bond length does not differ from the Si–C(Ar) length, the average values being 1·876 and 1·879 Å respectively. The Si–N bond attached to the four-membered ring (1·719 Å) is three standard deviations shorter than the cyclic (1·744 Å) and chain (1·738 Å) Si–N bonds.