The supramolecular assembly of the [(C6H5)2P(O)(NHC5H4N)]2HgI2 complex driven by the N–H...X, C–H...X, pi...X (X = O, pi), and C–H...I contacts is studied. The title molecule is the first mercury complex with a neutral (C)2P(O)(N)-based ligand, and the mercury atom adopts a geometry intermediate between pyramid and see-saw configurations. The interplay between intramolecular N–H...pi, O...pi, and C–H...pi contacts and the conformations of phenyl rings with respect to the P=O group is discussed. One ligand shows +ap–sp and +ac+sc conformations based on the C–C–P=O torsion angles and the other ligand shows +sc+ap and +ap–sp conformations (ap = antiperiplanar, sp = synperiplanar, ac = anticlinal and sc = synclinal). In the 13C{1H} NMR spectrum, the doublet signals are revealed for all of the carbon atoms of phenyl group (1J, 2J, 3J and 4J), and for the two ortho carbon atoms of pyridine moiety (2 * 3J), due to the coupling with phosphorus. Molecular Electrostatic Potential (MEP) calculation was performed to visualize charge distribution across the molecule.

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