Exploration of novel phenyl mercury tetrazole‐thione complexes: Characterization and investigating the impact of diamine ligands on enhanced hydrogen storage

Ten mixed‐ligand phenyl mercury(II) complexes containing 1‐methyl‐1H‐tetrazole‐5‐thiol (HmtzS) ( 1 ) and phosphine or amine ligands. These complexes fall into two groups: [PhHg(mtzS){Ph 2 P(CH 2 )PPh 2 }] 2 ( 2 ) and [PhHg(mtzS){Ph 2 P(CH 2 ) n PPh 2 }] ( 3‐6 ), where n varies, and [PhHg(mtzS)(diamine)] ( 8‐10 ), with diamine choices being 2,2′‐bipyridyl (Bipy, 8 ), 1,10‐phenathroline (Phen, 9 ), or ethylenediamine (en, 10 ). These complexes were synthesized with moderate to high yields and characterized using various techniques. Characterization data revealed that the mtzS − ligand coordinates as a monodentate ligand through the thiolate sulfur atom in all complexes, adopting a tetrahedral geometry around the Hg(II) center. Furthermore, complexes [PhHg(mtzS)] ( 1 ) and its diamine derivatives ( 8‐10 ) were assessed for hydrogen storage at 77 K using the VTI method. Results demonstrated that the incorporation of diamines improves hydrogen storage capacity at low pressure. The precursor stored ( 1 ) 2.3 wt.% at 80 bar, while the other complexes showed storage capacities ranging from 2.9 to 3.86 wt.% at pressures of 45‐60 bar. Thermodynamic properties of the [PhHg(mtzS)(Bipy)] complex was calculated at three different temperatures. The results prove that the entropy was equal to 0.50543599 J/mol H 2 . K while the enthalpy equal to 0.0942638 KJ/(mol H 2 ).