Synthesis and structural study of some new phosphorus( v ) hydrazide compounds: spectroscopic evidence and a theoretical approach

New phosphorus( v ) hydrazide compounds containing the [–P(O)NHNHC(O)OR] fragment have been prepared by the reaction of mono- and di-chloro phosphoryl intermediates with methyl (R = CH 3 , 1–5 ) and tert -butyl (R = C(CH 3 ) 3 , 6–9 ) carbazates, and characterized by IR and multinuclear NMR spectroscopy. Molecular structures of 1 , 2 , and 5 have been established by X-ray diffraction analysis to investigate the relative orientation of the present moieties, resulting hydrogen bonding motifs and stabilizing intermolecular interactions. The impact of the intermolecular contacts on crystal packing has been further studied by Hirshfeld surface analysis. The dependence of experimental δ 31 P and 2 J PNH values on phosphorus substituents has been explored using natural bond orbital (NBO) analysis. Likewise, the reasons for maintaining the tetrahedral geometry around the phosphorus atom in the synthesized compounds and not rearranging to a trigonal bipyramidal one (in comparison with spirophosphoranes) have been investigated theoretically. Overall, the NBO results reveal the influential role of electronic delocalization and s-content in hybridization for the above-mentioned experimental evidence.