PUB - Publikationen an der Universität Bielefeld

The compounds SiCl4 and GeCl4 reacted with Me(2)NNMeLi in hexane to form dichlorobis(trimethylhydrazido)silane, SiCl2(NMeNMe(2))(2) 1 and tetrakis(trimethylhydrazido)germane, Ge(NMeNMe(2))(4) 2 in 51 and 50% yield, respectively. The liquid 1 (m.p. 6 degrees C) and solid 2 (m.p. 73 degrees C) decompose at temperatures greater than 100 and 140 degrees C, respectively. Both compounds can be slowly vaporised at ambient temperature in high vacuum. They have been characterised by spectroscopic techniques including NMR (H-1, C-13, Si-29), IR, mass and high-resolution mass spectrometry. Evidence for higher co-ordination of the silicon atom occurs from the Si-29 chemical shift (delta - 44.0). The crystal structure of 1 shows the N-beta atoms of the hydrazide ligands interacting with the silicon atom resulting in a 4 + 2 co-ordination, whereas no N-beta ... Ge interactions are detectable in the structure of 2. While the geometry at the N-alpha atom in 1 is completely planar, that of the corresponding atom in 2 is slightly pyramidal. Ab initio calculations have been carried out for the model systems SiCl2(N2H3)(2) 1a, GeCl2(N2H3)(2) 1b (both C-2v), and Si(N2H3)(4) 2a and Ge(N2H3)(4) 2b (both S-4) up to the MP2/6-31G* level of theory. The results lead to the prediction that the germanium compound analogous to 1 should have N-beta ... Ge interactions which are even stronger than the N-beta ... Si ones in 1.