PCCP does exist

Neutral and cationic [C-2,P-2] were investigated by a combination of mass s pectrometry and electronic structure calculations. The cationic [C-2,P-2](. +) potential energy surface including all relevant minima, transition state s and fragmentation products was calculated at the B3LYP/6-311G(3df) level of theory. The most stable structures are linear PCCP.+ 1(.+) (E-rel=0 kcal mol(-1)), a three-membered ring with exocyclic phosphorus c-(PCC)-P 2(.+) (E-rel = 40.8 kcal mol(-1)), and the rhombic isomer 3(.+) (E-rel = 24.9 kca l mol(-1)). All fragmentation channels are significantly higher in energy t han any of the [C-2,P-2](.+) isomers. Experimentally, [C-2,P-2](.+) ions ar e generated under high vacuum conditions by electron ionization of two diff erent precursors. The fragmentation of [C-2,P-2](.+) on collisional activat ion is preceded by rearrangement reactions which obscure the structural con nectivity of the ions. The existence and the high stability of neutral [C-2 ,P-2] were proved by a neutralization-reionization (NR) experiment. Althoug h an unambiguous structural assignment of the neutral species cannot be dra wn, both theory and experiment suggest that the long-sought neutral, linear PCCP 1 is generated using the NR technique.