A new bisphosphinamide: X-ray crystallography, spectroscopy andthermogravimetry

Phosphinamides, with a C۲P(O)N fragment, are well-known for flame-retardancy properties[۱]. In this work, the synthesis, spectroscopy, thermogravimetry and X-ray crystallography of N,N'-(cyclohexane-۱,۴-diyl)-bis(P, P-diphenylphosphinic amide) are studied. The compoundcrystallizes in the monoclinic space group C۲/c. The asymmetric unit is composed of one half ofthe molecule, and the complete molecule is generated by an inversion element. The P atom has adistorted tetrahedral C۲P(O)N enviroment, and the maximum and minimum bond angles atphosphorus are related to N—P═O (۱۲۰.۲۳ (۶)°) and N—P—C (۱۰۱.۹۵ (۷)°). The bond-anglesum at nitrogen (about ۳۵۳°) confirms its sp۲ character. The P═O bond length (۱.۴۸۶۴ (۱۱) Å) isslightly longer than the typical phosphorus-oxygen double bond length and is comparable tothose in analogous compounds [۲, ۳]. The P—N bond length (۱.۶۴۰۷ (۱۳)Å) is standard forstructures with a C۲P(O)N skeleton [۳]. The NH unit adopts a synclinal orientation with respectto the P═O group. In the crystal structure, the molecules are aggregated through N—H…Ohydrogen bond in a two dimensional assembly along the bc plane. The ۳۱P NMR spectrum showsone signal at ۱۹.۹۱ ppm indicating the high purity of the compound. In the IR spectrum, the bandcentered at ۳۱۳۳ cm–۱ corresponds to the N—H stretching. The TGA exhibits the startingdecomposition point at about ۲۵۰ °C.

Keywords:

bisphosphinamide , Crystal structure , Thermogravimetric analysis