The compounds SiCl₄ and GeCl₄ reacted with Me₂NNMeLi in hexane to form dichlorobis(trimethylhydrazido)-silane, SiCl₂(NMeNMe₂)₂1 and tetrakis(trimethylhydrazido)germane, Ge(NMeNMe₂)₄2 in 51 and 50% yield, respectively. The liquid 1(m.p. 6 °C) and solid 2(m.p. 73 °C) decompose at temperatures greater than 100 and 140 °C, respectively. Both compounds can be slowly vaporised at ambient temperature in high vacuum. They have been characterised by spectroscopic techniques including NMR (¹H, ¹³C, ²⁹Si), IR, mass and high-resolution mass spectrometry. Evidence for higher co-ordination of the silicon atom occurs from the ²⁹Si chemical shift (δ–44.0). The crystal structure of 1 shows the N_β atoms of the hydrazide ligands interacting with the silicon atom resulting in a 4 + 2 co-ordination, whereas no N_β⋯ Ge interactions are detectable in the structure of 2. While the geometry at the N_α 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)₂1a, GeCl₂(N₂H₃)₂1b(both C_2v), and Si(N₂H₃)₄2a and Ge(N₂H₃)₄2b(both S₄) 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_β⋯ Ge interactions which are even stronger than the N_β⋯ Si ones in 1.