PUB - Publikationen an der Universität Bielefeld

The reactions of 1,2-bis(bromosilyl)ethane and 1,3-bis(bromosilyl)propane with anhydrous hydrazine lead to the two bicyclic silylhydrazines 1,6-diaza-2,5,7,10-tetrasila[4.4.0]bicyclodecane (1) and bis(1-aza-2,6-disila-1-cyclohexyl) (2), respectively. For compound 1, a distillable liquid with mp 7-degrees-C, the low-temperature crystal structure determination has shown a bicyclic configuration with the N-N unit shared by two slightly twisted, chair-formed heterocycles. The N-NSi2 Units are virtually planar but not orthogonal relative to each other owing to conformational restraints. In crystals of compound 2, mp 57-degrees-C, two six-membered rings each in a half-chair conformation are linked solely through the hydrazine N- N bond. The two planar NNSi2 units are at right angles as expected for a nonforced tetrasilylhydrazine geometry. The N-N bond is longer in 1 than in 2. Variable-temperature H-1 C-13 N-15, and Si-29 NMR spectra of both hydrazines have been measured, and the barrier of ring inversion of 1 has been determined.