Iminophosphorane-substituted proton sponges. Part 3. Preparation and crystal structure of three salts of protonated 1-dimethylamino-8-triphenylphosphoranylideneammonionaphthalene

Abstract

Results of the crystal structure analysis of three 1-dimethylamino-8-triphenylphosphoranylideneammonionaphthalene salts are described. The ‘extra proton’ has been found to bind to the nitrogen atom of the iminophosphorane group, being engaged in a strong intramolecular contact [N ⋯ N = 2.519(3), 2.543(4), 2.571(6)Å; N–H ⋯ N = 154(6), 155(6) and 147(6)° for Br^–, BF₄^– and PF₆^– salts, respectively] which is shorter in two salts than those displayed by the 1,8-bis(dimethylamino)naphthalene salts of Br^–, BF₄^– and TeOF₅^–, which are considered as ‘proton sponges’[2.555(3), 2.562(2) and 2.574(3)Å, respectively].