Gas phase ion chemistry and ab initio theoretical study of phosphine .1.

Gas phase ion processes of phosphine have been studied by theoretical calculations and experimental techniques. AZ, initio quantum chemical calculations have been performed on the ion/molecule reactions starting from P+ in PH3, as they have been observed by ion trapping. P+ gives P2Hn+ (n = 1,2) product ions with loss of H-2 or H in different pathways and also reacts in charge-exchange processes to form PH3+ The energies of transition structures, reaction intermediates, and final products, as well as their geometrical structures have been determined by theoretical methods. The initial step is formation of a tripler P2H3+ adduct of C-3 upsilon symmetry (P-PH3+). A hydrogen atom can either be directly lost from the tetracoordinated phosphorus, or first undergo a shift to the other P atom (H-P(+)-PH2), followed by P-H bond dissociation. Dissociation of H-2 from P2H3+ can also occur from both the initial P-PH3+ and HP+-PH2 species yielding PPH+. The heats of formation of the P2Hn+ ionic species have also been computed and compared with experimental data reported in the literature. (C) 1997 American Institute of Physics.