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Institute
Eight-membered rings of the composition [SO2(NR)2PR′]2 3a-d with R = CH3, C2H5, and R′ = CH3, C6H5, were prepared from substituted sulfamides and dichlorophosphanes in the presence of a tertiary amine. These molecules were characterized on the basis of 1H and 31P NMR investigations and of mass spectra. 3 a reacts with phosphorus pentachloride to yield the spirocyclic derivative 4 with the phosphorus atom in the center of two four-membered rings. Methyliodide reacts with 3 a and 3 b under opening of the eight- membered ring and formation of phosphonium salts. The structure of 3 b is discussed in detail. 8b crystallizes in the orthorhombic space group Pna 21 with a = 12.60(0), b = 13.27(1), c = 12.62(4) Å.
The neutral title compound, 8,8-bis(dimethylamino)dibenzo-[a,d]-heptafulvene, exhibits a first vertical ionization potential of only 6.98 eV and, therefore, can also be oxidized by AlCl3 in H2CCl2 solution. The radical cation generated shows a complex multiplet signal pattern, which is assigned based on additional ENDOR measurements. The photoelectron (PE) and ESR spectra of the 112 valence electron molecule are interpreted by “pararneter-optimized” HMO and by geometry-optimized MNDO calculations, which both suggest a non-planar π-type ground state with most of the charge and the spin distributed over the dibenzoheptatriene part of the radical cation.