Аннотация:We prepared 1,1,3,3-tetramethyl-1,3-disila-2-oxa[3]ferrocenophane Fe(η5-C5H4)2-(SiCH3)2O 1 via the reaction of 1,1′-dilithioferrocene TMEDA with dichlorodimethylsilane followed by hydrolysis. Crystals 1A obtained from sublimation crystallize in the space group P-1 in analogy to the crystal structure recently published [1]. A new crystal structure 1B of compound 1 could be obtained by slow evaporation of the solvent (CDCl3) in the NMR tube. 1B crystallizes in the orthorhombic space group P212121. Whereas so far there have only been reports on a mixture of 3 conformers, we have succeeded in isolating one single conformer.