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Eight-membered heterocycles containing two phosphorus atoms. X-ray diffraction and nuclear magnetic resonance studies of 2,6-dimethyl-1,3-dioxa-2,6-diphosphacyclo-octane 2,6-disulphides and 2,6-diselenides

par Piccinni Leopardi, Carla ;Reisse, Jacques ;Germain, Gabriel;Declercq, Jean-Paul;Van Meerssche, Maurice;Jurkschat, K.;Mügge, Clemens;Zschunke, Adolf;Dutasta, Jean-Pierre;Robert, Jean Bernard
Référence Journal of the Chemical Society. Perkin Transactions 2, 1, page (85-92)
Publication Publié, 1986

Article révisé par les pairs

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Résumé :

trans- and cis-2,6-dimethyl-1,3-dioxa-2,6-diphosphacyclo-octane 2,6-disulphides (1) and (2), and trans- and cis-2,6-diselenides (3) and (4), have been investigated by means of 1H (2D, J-resolved), 13C, and 31P n.m.r. spectroscopy and X-ray diffraction. In the solid state the cis-isomers adopt a crown conformation and the trans-isomers a boat-chair conformation. The orientations of P-X (X = S or Se) and P-Me bonds are quasi-axial and quasi-equatorial, respectively. Room-temperature n.m.r. data can be interpreted on the basis of the X-ray data. A fast enantiomerization between two boat-chair conformations of opposite chirality characterizes the trans-isomers, whereas the cis-isomers exist mainly in a crown conformation similar to that observed in the crystal.