摘要：

The Stabilization of the Trigonal-Bipyramidal Ground States of Spirocyclic Pentaorganyl-phosphoranes and -arsoranes According to the 1 H n.m.r. spectra the bis (4,4′-dimethyl-2,2′-biphenylylene)(8-Y-1-naphthyl)-phosphoranes 5a – g have trigonal-bipyramidal ground states, in which the 8-Y-1-naphthyl groups are situated in a rigid position nearly parallel to the equatorial plane. Furthermore, in the phosphoranes 5g and 1c the rotation of the dimethylamino group is also frozen. No indication of an inner onium-ate structure could be found for the phosphoranes 5f , g and 1b, c on the basis of 1 H and 31 P n.m.r. spectra. The total signal equilibrations observed at elevated temperatures (exception: 5g ) can be explained by pseudorotations of the spiro skeleton assuming concomitant rotation of the 8-Y-1-naphthyl groups. The stereochemistry of the analogous arsenic compounds 10a – c , e , h can be interpreted with the same model.

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