A structural study of 1,8-bis(dimethyl phosphonito) naphthalene and related crowded chalcogeno derivatives

1,8-Bis(dimethylphosphonito) naphthalene Nap[P(OMe)2]2(Nap = naphthalene-1,8-diyl) and a complete series of its mono- and dioxidized phosphonato counterparts Nap[P(E)(OMe)2]2(E = O, S, Se, lone pair and all their permutations) were prepared and fully characterized by X-ray crystallography and multinuclear NMR, IR, Raman and MS. Molecular distortion due to non-bonded substituent interactions was studied as a function of the bulk of the phosphorus substituents. The least and most strained molecules in the series are Nap[P(OMe)2]2 and Nap[P(Se)(OMe)2]2 with non-bonding P...P distances of 2.91 and 3.79 (angstrom) respectively.