Carbon phosphide anions

Stable carbon phosphide anions have been prepared by the reaction of small carbon anions (C(n)(-)n=3-9) with gaseous P-4. The C-n(-) anions, produced by laser ablation, were trapped and reacted in a Fourier transform ion cyclotron resonance mass spectrometer. The compositions of the anions formed were CnP, CnP2, C4P4, CnP5. All the anions for n=3-9 are covered in this paper and have been investigated theoretically using density functional calculations, incorporating gradient corrections and numerical basis sets. The [CnP](-) and [CnP2](-) anions are calculated to be linear, with the P atoms at one and both ends of the C,, chain, respectively. The [C4P4](-) anion is the only ion containing four P atoms, and never has more than minor intensity; three structures close in energy are calculated for [C4P4](-), with the most stable possessing a CP4 mononocycle at the end of the C-4 chain. The [CnP5](-) anions observed when n=4, 6 or 8 have a lowest energy structure with one phosphorus atom at one end of the chain and a P-4 ring at the other end.