Photoelectron Spectra of λ‐Di‐ and ‐Triphosphabenzenes

The He(I) photoelectron spectra of 1,1,3,3‐tetrakis(dimethyl‐amino)‐1λ 5 ,3λ 5 ‐diphosphabenzene ( 1a ), 1,1,3,3,5,5‐hexakis(dimethylamino)‐1λ 5 ,3λ 5 ,5λ 5 ‐ triphosphabenzene ( 2a ), 4‐ tert ‐butyl‐1,1,3,3‐tetrakis(dimethylamino)‐1λ 5 ,3λ 5 ,5λ 3 ‐triphosphabenzene ( 3a ), and the substitution products 4a and 5a of 1a have been recorded. The assignment of the PE spectra is based on a comparison of the PE spectra of related species with the MO calculations carried out by using the MNDO procedure. The investigations reveal that the first bands correspond to π‐MOs which are mainly localized on the C atoms of the six‐membered ring. The MO calculations predict a strong negative net charge for the ring carbon atoms adjacent to the P atoms and strong positive net charges for the P atoms.