V. Becker, W. Massa, R. Schmidt
Aug 3, 1982
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Abstract
Bis(dimethylamino)-1,3-diphenyl-l, 3-diphosphetane %a which is isolated as a by- product in the synthesis of (E)-(dimethy1amino)methylidene-phenylphosphine la crystallizes in the monoclinic space group P2,/c. The dimensions of the unit cell determined at -65 & 5°C are: a = 1004(1); b = 1018(3); c = 1873(2) pm; = 105.15(8)"; Z = 4. As it is shown by a low tempera- ture X-ray structure determination (Rg = 3.5%) the phenyl groups are placed above and the di- methylamino groups below the folded 1,3-diphosphetane ring; the molecule with its differently twisted substituents, however, deviates considerably from point symmetry mm2. The dihedral angle between the Pl-Cln-P2 planes (n = 1 or 2) is found to be 153". The relatively long Pn-Cln bond distances (187 to 191 pm) indicate a strained ring system; in solution 2 a decomposes to some extent and forms monomeric la again. Further characteristic average bond distances and angles are: Pn-C4n (phenyl) 184; C-N 146 pm; P1-Cln-P2 93"; C11-Pn-Cl2 84" and Pn-Cln-Xn 116".