Inorganic chemistry laboratory experiment on an energetic nickel (II) coordination compound, aimed at third-year undergraduate students

Umit B Demirci,Laurent Bernaud

doi:10.1515/cti-2020-0029

Abstract

Abstract This inorganic chemistry laboratory experiment, aimed at third-year undergraduate students, focuses on an energetic coordination compound, tris(hydrazine)nickel(II) nitrate [Ni(N2H4)3][NO3]2. As long as the solid is not subject to mechanical stimuli (impact and friction), it can be safely synthesized and handled. In our laboratory conditions (see supplementary information), the experiment includes synthesis of [Ni(N2H4)3][NO3]2 in two different morphologies, visual inspection of the samples, analysis by IR spectroscopy, checking the crystallinity by powder X-ray diffraction, 3D visualization of the crystal structure by means of a free program, and observation by scanning electron microscopy. In that respect, the experiment, as a whole, introduces students to nickel(II) complexes, coordination compounds, energetic materials, sonochemical and morphology-controlled syntheses, and a 3D visualization program for crystal structures and structural models. This laboratory experiment is also proposed in the form of alternate (light) versions so that it can be adopted in another inorganic chemistry laboratory that may have restrictions in terms of equipment, and in another third-year curriculum.

Highlights

Hexaaquanickel(II) [Ni(H2O)6]2+ is a typical octahedral complex where the Ni2+ metal center binds to six H2O ligands
The experiment, as a whole, introduces students to nickel(II) complexes, coordination compounds, energetic materials, sonochemical and morphology-controlled syntheses, and a 3D visualization program for crystal structures and structural models. This laboratory experiment is proposed in the form of alternate versions so that it can be adopted in another inorganic chemistry laboratory that may have restrictions in terms of equipment, and in another thirdyear curriculum
The spectrum favorably compares with previous results (Tignol & Demirci, 2019; Wang et al, 2009), confirming the successful synthesis of [Ni(N2H4)3]

Summary

Introduction

Hexaaquanickel(II) [Ni(H2O)6]2+ is a typical octahedral complex where the Ni2+ metal center binds to six H2O ligands. These ligands can be substituted by ammonia NH3, a stronger Lewis base, to form hexaamminenickel(II) [Ni(NH3)6]2+. With the ligand ethylenediamine C2H4(NH2), tris(ethylenediamine)nickel(II) [Ni((NH2)2C2H4)3]2+ forms. These complexes differ in color (green, blue and purple respectively) due to differences in energy between the degenerate t2g–eg orbitals which is in line with the differences in the Lewis basicity of the ligands (Roberts & Field, 1950; Shakhashiri, Dirreen, & Juergens, 1980; Summerlin, Borgford, & Ealy, 1987). Hydrazine N2H4 is another ligand of Ni2+, leading to tris(hydrazine)nickel(II) [Ni(N2H4)3]2+. [Ni(N2H4)3][NO3]2 is less sensitive to mechanical stimuli like impact and friction

Methods

Results

Conclusion