Synthesis, characterization, crystal structures, Hirshfeld surface analysis and theoretical calculations of some new bisphosphoramidate derivatives and novel binuclear triorganotin(IV) complexes with diphosphoryl ligand

Abstract

A series of new bisphosphoramidate and (thio)phosphoramidate derivatives with the general formula R1R2P(X)–Y–P(X)R1R2 have been synthesized and characterized by IR and NMR spectroscopies (L1–L12). The crystal structure of compound 1,4-[(C2H5O)2P(S)(CH2)3NH]2C4H8N2 (L4) is also investigated by X-ray diffraction analysis. Two novel organotin(IV) complexes μ-{1,4-[(C6H5)2P(O)(CH2)3NH]2C4H8N2}[SnR3Cl]2, R3SnCl (R = phenyl/butyl), C1 and C2, respectively, are prepared by the reaction of new diphosphoryl ligand L1 and R3SnCl under different conditions. C1 and C2 are characterized by IR and NMR spectroscopies and X-ray crystallography diffraction analysis. X-ray analysis illustrates that both complexes have similar structures containing binuclear triorganotin(IV) skeletons and ligand coordinates in a bridging mode through two phosphoryl groups. Sn(IV) coordination geometries are distorted trigonal bipyramidal (TBP) for C1, and C2 structures contained binuclear arrangement with two SnPh3Cl/SnBu3Cl groups linked via the bridging diphosphoryl ligand. The organization of the crystal structures and the intermolecular interactions are discussed. Hirshfeld surfaces and two-dimensional fingerprint plots are used to study short intermolecular contacts in C1, C2, and L4. Finally, the influence of chain length and the effects of various substituents on P=O and P=S bond strength in synthesized ligands (L1–L12) and optimized ligands (L13–L17) are theoretically investigated by NBO analysis to survey the character of mentioned bonds in these ligands. The AIM analysis is also used to determine the nature of the P=O bond in L1 and also P=O and O⋯Sn4+ bonds in C1 and C2. Results show ionic character for O⋯Sn4+ interaction in both complexes and mostly electrostatic character for P=O bond in the free ligand, but with a little shift to the covalent character after the complexation.