Iminophosphorane-substituted proton sponges. Part 2. Preparation and crystal structure of four phosphoranylideneammonionaphthalene derivatives

Abstract

Crystal structure analysis of salts of one monosubstituted (1) and three peri disubstituted naphthalene derivatives (2, 3 and 4) are described. The strong repulsion between the nitrogen lone pairs in neutral structures is replaced by an intramolecular N⁺–H ⋯ N interaction in compounds 2, 3 and 4 giving rise to a similar distortion in the naphthalene skeleton in each case, an inward bending of the exocyclic C_aryl–N bonds and a decrease of the N ⋯ N distance: [2.606(4)–2.533(6)Å]versus 2.792(3)Å found in 1,8-bis(N,N-dimethyl)naphthalene and 2.716(11) and 2.739(10)Å in 1,8-diaminonaphthalene. This behaviour is characteristic of proton sponges.