Variation of Nucleophilicity NHnA of Atoms A in Hydrides HnA with the Group and Row of A within the Periodic Table.

Abstract

Nucleophilicities NHnA of hydrides of atoms A acting as hydrogen-bond acceptors in complexes HnALHX are reported. The HnA initially chosen were HB, H2C, H3N, H2O and HF, that is from Groups 13, 14, 15, 16 and 17, respectively, of Row 1 of the Periodic Table.  The Lewis acids HX involved in the complexes were HF, HCl, HBr, HI, HCCH, and HCP.  Nucleophilicities were determined from dissociation energies De for the process HnALHX = HnA + HX by  using De = cNHnA.EHX, where EHX are electrophilicities of the Lewis acids HX.  This procedure was also followed for hydrides HnA  where the atoms A were from the same Groups, but from Rows 2, 3, and 4 of the Periodic Table. The order of NHnA values found was Row 1 > Row2 ~ Row3 ~ Row 4 in each of the Groups 13, 15, 15, 16 and 17, with a large decrease from Row 1 to Row 2 but with small decreases from Rows 2 to 3 to 4. The series RgLHX, was similarly investigated to give the order of nucleophilicities Rg = Xe > Kr > Ar. > Ne, which is reversed from that in the hydrides of Groups 13 to 17.