| Abstract: | Metal Derivatives of Molecular Compounds. VIII. catena-Poly(2,5,8-trioxanonane-O2,O5) lithium-methylphosphanide] — a Compound with a meso-Helix Structure Studies of Fritz et al. 10] showed methylphosphane to be lithiated at ?60°C in 1,2-dimethoxyethane or bis(2-methoxyethyl) ether solution by stoichiometric amounts of lithium n-butanide in n-hexane. After removing the hydrocarbons almost completely by distillation and cooling the solutions to ?60°C again, colourless square crystals of (1,2-dimethoxyethane-O,O′)lithium ( 1 ) and (2,5,8-trioxanonane-O2,O5)lithium methylphosphanide ( 2 ) precipitate. As shown by an X-ray structure determination (monoclinic, P21/n; a = 805.5(1); b = 1820.6(2); c = 851.5(1) pm; β = 116.76(1)° at ?100 ± 3°C; Z = 4 formula units; R = 0.034) complex 2 forms a polymer which has the shape of an up to now scarcely noted meso-helix. Four-coordinated lithium is bound to two phosphorus (P? Li 252.9 and 253.2 pm; P? Li? P 131.8°; Li? P? Li 132.1°) and to two oxygen atoms (Li? O 203.9 and 206.8; O …? O 270.7 pm; O? Li? O 82.5°) of the inherently tridentate 2,5,8-trioxanonane ligand. As compared to the standard value (185 pm) the P? C distance (187.4 pm) is slightly lengthened. Structure determinations of (2,5,8-trioxanonane-O2,O5,O8) lithium 1-(phenylsulfonyl)alkyl compounds published some years ago 26, 27], allow a comparison of molecular parameters characteristic for the twofold or threefold coordinating chelate ligand. |
