Starke P – P‐Wechselwirkungen in Tetraphosphacubanen, PE‐spektroskopische Untersuchungen

Strong P – P Interactions in Tetraphosphacubanes. A PE‐Spectroscopic Investigation The comparison between the first peaks of the PE spectra of (tBuCP) 4 ( 2a ) yields about the same ionization energy for the first peak (4t 2 ), but a large difference (ca, 0.8 eV) for the second peak ( 1t 1 ). This difference is due to a strong interaction of the n orbitals at P with the P‐C σ bonds in 1. This n/σ interaction is much smaller in the case of 2 . The energy difference between 2 4T 2 and 2 3A 1 , corresponding to the lone‐pair combinations of the n orbitals at the P atoms, amounts to ≥ 3.4 eV for 1a and is estimated at ≥ 1.6 eV for 2a. The net charges for the P atoms in 1 are calculated to be positive, those for the C atoms negative. In the case of 2 negative values result for P and positive values for the net charges at Si.