New alkali metal coordinations by chelating siloxazane units within molecules of the general formula [X-N-SiMe2-O-SiMe2-N-X](2)M-4

New solvent free alkali metal amides with Si-O-Si bridges of the general fo rmula [X-N-SiMe2-OSiMe2-N-X](2)M-4 (X = Bu-t (1), SiMe3 (2), (SiMe2Bu)-Bu-t (3) with M = Li; X = Bu-t (4), SiMe3 (5) with M = Na; X = Bu-t mit M = K, Li (6)) have been synthesised and characterised by spectroscopic means. X-r ay structure analyses of the six metal derivatives reveal a common structur al principle: the four metal atoms within the molecules are incorporated be tween two molecular halfs and form the bonding links between the two parts. The central molecular skeleton of the molecular halfs consists of a zig-za g chain N-Si-O-Si-N. This chain is connected to the second one either ideal ly or approximately by S-4 (4) symmetry. The point symmetries within the cr ystal are either S-4 (4) (compounds 2 and 4), C-2 (2) (compound 6), and C-1 (1) (compounds 3 and 5). Compound 1 is special in different aspects: the m olecule has the high crystallographic point symmetry D-2d (4m2) and the lit hium atoms occupy split atom positions (in a similar way as in compound 2). The high symmetry of 1 as well as the split atom positions of the lithium atoms are a consequence of dynamics within the crystal.