The gas-phase route from Cp*2P6 to neutral hexaphosphorus

Density functional theory has been applied to gain insight into the fragmentation and redox behavior of CpnP6+/0 and Cp*nP6+/0 cations and neutral species (n = 1, 2) in the gas phase. Particular attention is paid to the previously reported generation of neutral hexaphosphorus upon high-energy collisions of the Cp*P6+ cation. Theory provides an explanation for the experimentally observed effect that collisional electron transfer to the Cp*P6+ cation is negligible in that the associated Franck-Condon factors are predicted to be unfavorable. In contrast, dissociation of Cp*P6+ into Cp*(+) + P6 has a relatively low energy demand, thereby accounting for the efficient formation of neutral P6 in the gas phase. Theoretical exploration of the parent compound Cp2P6 reveals that the unsubstituted cyclopentadienyl ligand is much less suitable in this respect, thereby sustaining the previous suggestion that Cp* is a particularly good leaving group.