The focus of this work is the preparation and characterization of mixed ligand mercury (II) complexes with involvement of 4-fluoro-2-cyanoaminothiophenalate (F-CAT) as the initial ligand and amine or triphenylphosphine (PPh3) as an additive ligand. The complexes were prepared by a straight forward method by increasing the solution of HgCl2 in ethanol and F-CAT and then adding the corresponding co-ligands (AlJanabi et al., 2017). The synthesized complexes were further scrutinized using various spectroscopy techniques such as UV-Visible, IR, and NMR. UV–Vis profiles further exhibited bands characteristic of LMCT transitions, which further validated the successful coordination of F-CAT and the co-ligands to the mercurate ion. Additional support to the observed successful coordination was extracted from the shifts in the proton resonance frequency signals obtained from 1H NMR. Furthermore, 31P NMR study of Hg(F-CAT) PPh3 exhibited that PPh3 has coordinated to the mercury center. The similarities to literature results underlined our results as coherent with the existing pattern of mercury (II) complexation. The investigations presented in this work advance the overall knowledge of mercury (II) coordination chemistry and provide unique visions for the use of HELM in catalysis, material sciences, and medicinal chemistry.