Studies toward Isolation and Characterization of Aminated Nickel (II) Hydrate Intermediates

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Authors
Dailey, Tyler
Lohar, Noah
Advisor
Rowley, John
Coates, Rebecca
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Date of Issue
2024
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Title
Studies toward Isolation and Characterization of Aminated Nickel (II) Hydrate Intermediates
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Abstract
Metal-ligand coordination complexes are formed by step-wise ligand substitutions when ligands are introduced to metal ions. However, it is common for only the final product to be isolated in these types of reactions. Herein, a proposed ligand-exchange method for isolating and quantifying the stoichiometry of the intermediates of the nickel(II) hexahydrate to nickel(II) hexamine reaction is reported. The ligand-exchange method applied held the molar concentration of nickel(II) hexahydrate constant while varying molar ratios of reacting amine. Under these controlled conditions, stable isolated nickel(II) n-ammonia n-hydrate intermediate species were produced at all mole ratios investigated, whereas the nickel(II) hexamine was only formed under excess reacting ammonia. Stoichiometries of the aminated intermediate species were measured using UV-vis spectroscopic analysis due to the color difference between the hydrated and aminated species in an aqueous environment. The wavelength at which the hydrated species' absorbance was highest (λmax) was 394nm, and the λmax of the aminated species was 363nm. The isolated aminated intermediate species blue-shifted 5nm from the hexahydrate reactant species. From this, the intermediate species stoichiometry was determined to be 1:1.5, water ligands to ammonia ligands, coordinated to the nickel(II) center.
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Chemistry and Physics