METAL DERIVATIVES OF MOLECULAR-COMPOUNDS .8. -TRIOXANONANE-O(2),O(5))LITHIUM-METHYLPHOSPHANIDE] - A COMPOUND WITH A MESO-HELIX STRUCTURE

Studies of Fritz et al. [10] showed methylphosphane to be lithiated at -60-degrees-C in 1,2-dimethoxyethane or bis(2-methoxyethyl) ether1) s olution by stoichiometric amounts of lithium n-butanide in n-hexane. A fter removing the hydrocarbons almost completely by distillation and c ooling the solutions to -60-degrees-C again, colourless square crystal s 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 st ructure determination (monoclinic, P2(1)/n; a = 805.5(1); b = 1820.6(2 ); c = 851.5(1) pm; beta = 116.76(1)degrees at - 100 +/- 3-degrees-C; Z = 4 formula units; R = 0.034) complex 2 forms a polymer which has th e shape of an up to now scarcely noted meso-helix. Four-coordinated li thium is bound to two phosphorus (P-Li 252.9 and 253.2 pm; P-Li-P 131. 8-degrees; Li-P-Li 132.1-degrees) and to two oxygen atoms (Li-O 203.9 and 206.8; O..O 270.7 pm; O-Li-O 82.5-degrees) of the inherently tride ntate 2,5,8-trioxanonane ligand. As compared to the standard value (I 85 pm) the P-C distance (t 87.4 pm) is slightly lengthened. Structure determinations of (2,5,8-trioxanonane-O2,O5,O8)lithium 1-(phenylsulfon yl) alkyl compounds published some years ago [26, 27], allow a compari son of molecular parameters characteristic for the twofold or threefol d coordinating chelate ligand.