XRD Study of β-Aminophosphine and its Perfluoro-2,1,3-Benzothiadiazole Based Oxide

Abstract

N-(2-(diphenylphosphino)ethyl)-4,6,7-trifluoro-2,1,3-benzothiadiazol-5-amine (Ph₂PCH₂CH₂NH-btd-F₃ (PCCN)) is prepared by the reaction of 4,5,6,7-tetrafluoro-2,1,3-benzothiadiazole (btd-F₄) with 2-(diphenylphosphino)ethyl-1-amine (Ph₂PCH₂CH₂NH₂) leading to the nucleophilic substitution of F^– by a phosphinamide fragment (Ph₂PCH₂CH₂NH)^– in btd-F₄. Phase 1 (a product of cocrystallization of PCCN (85%) and its oxide Ph₂P(O)CH₂CH₂NH–btd-F₃ (POCCN, 15%)) is obtained by the separation of the mixture of products by thin-layer chromatography and subsequent evaporation of the solution. POCCN is obtained preparatively using the oxidation of PCCN by hydrogen peroxide. Phase 1, two polymorphs of POCCN (2 and 4), and the POCCN·C₆H₆ solvatomorph (3) are characterized by XRD. The P–C–C–N fragment in these phases adopts either a bent gauche-conformation with an intramolecular N–H⋯O hydrogen bond or an anti-conformation stabilized by a pair of intermolecular hydrogen bonds combining the molecules into a dimer. According to the DFT data, gauche-POCCN has a larger negative electrostatic potential at F and N than anti-POCCN, i.e. the btd-F₃ fragment of the first conformation is more likely to participate in predominantly electrostatic intermolecular interactions.