CHARACTERIZATION OF (P(-MOLECULE CLUSTERS OF FIRST-ROW HYDRIDES()L(X))L(Y) ION)

Ab initio calculations of phosphorus ionic clusters of the type PL(+). L, PL(2)(+). L, PL(3)(+), and PL(4)(+), with L = NH3, OH2, and FH, in both triplet and singlet states have been carried out, in order to de termine their geometries and binding energies. The nature of the bindi ng has also been extensively studied by means of both the topological analysis of the total electron charge density and the natural bond orb ital analysis. When the ligand is bound as a second ligation shell thr ough a formal hydrogen bond, significant cooperative effects between t he two ligand shells have been detected. Substantial covalency is foun d for these hydrogen bonds, along with the weakening of the hydride bo nd with the inner ligand and the reinforcing of the bond between the i nner ligand and the phosphorus. These processes are greatly favored fo r the singlet state of the phosphorus, and for the case of ammonia and water ligands, conversion reactions leading to PXH(n-1). XH(n+1)(+) c omplexes are observed. It has been found that the maximum number of li gands bound to (P-3P+ is two, whereas that maximum is ligand dependent in the case of (D-1P+, with two for NH3, three for OH2, and four for FH. We have also observed that soft ligands present a sharp decrease i n successive binding energies to phosphorus, whereas hard ligands show smoother variations. Finally, for most cases, the addition of the new ligand as a second ligation shell is favored with respect to the dire ct addition to the phosphorus, since cooperative effects make more eff icient the donation of electronic charge to the phosphorus ion.