GAS-PHASE ELECTRON-DIFFRACTION STUDY OF 1-CHLORO-2,4-DIMETHYL-1,2-DIHYDRO-1,5,2,3-PHOSPHAOXADIAZOLE

Abstract Earlier gas phase electron diffraction data on 1-chloro-2,4-dimethyl-1,2-dihydro-1,5,2,3-phosphaoxadiazole (I) obtained by these authors are treated using up-to-date developments in structure analysis and the conclusion of a considerable elongation of the P-Cl bond in chlorinated aminophosphines is subst anti ated. This bond length ( r a ) is found to be 2.168(4) A in I, i.e. far larger than the sum of the covalent radii (2.09 A). The r a parameters of the oxadiazaphospholene ring containing the NC double bond refine to the following values (bond lengths in A, angles in degrees): 1.699(6); PO, 1.628(5); weighted average , 1.403(9); NC, 1.277(8); NPO, 91.1(0.6); PNN, 108.7(1.0); POC, 109.3(1.0); NNC, 112.0(1.8); NCO, 114.0(2.0). The ring has an envelope-like nonplanar conformation with the P atom in the flap position. The dihedral angle between the NPO plane and the least-squares plane of the O-CN-N fragment is 20.0(2.5)°. The P–Cl bond is in the axial position. The amine nitrogen linked with phosphorus has a practically planar bond configuration (the sum of the valence angles at N is 357.7°).