Cross-coupling is a type of reaction capable of forming carbon-carbon bonds with the aid of a transition metal catalyst. Mechanistic studies electrochemical cross electrophile coupling reveal stoichiometric data and intermediate potentials which can lead to the development of novel strategies for carbon-carbon bond formation. This technique can be useful for production of pharmaceuticals and other industrial chemicals; therefore, it is crucial to study the catalysts that drive the mechanism. Monitoring potentials throughout a reaction process allows for more control over the chemical reaction and offers insight on favorable conditions that can lead to improved reaction selectivity and/or catalyst design. This investigation aimed to characterize (2,2’-Bipyridine) dichloronickel(II), [NiCl<sub>2</sub>(bpy)], and mechanistically study its catalytic cycle through a series of elementary reactions. This complex was synthesized using air-free techniques and characterized using nuclear magnetic resonance (NMR) spectroscopy, ultraviolet-visible spectroscopy, and cyclic voltammetry. Inert conditions helped improve synthesis procedures and data collection by distinguishing between features of atmospheric oxygen and the analyte. The geometry of the nickel bipyridine complex was predicted with an Evan’s method experiment using NMR. Further characterization with cyclic voltammetry was used to study the redox features of the complex at varying scan rates and scan directions. The use of electrochemical methods eliminates the need for a sacrificial metal reductant, thus improving atom economy, cost efficiency, and reaction selectivity.  Reductive features of [NiCl<sub>2</sub>(bpy)] demonstrated limited reversibility despite increases in scan rate. Preliminary data of integrated voltammograms’ reductive features in relation to a ferrocene standard were used to predict electron stoichiometry of reductive features. The peak currents were also graphed against the square root of scan rate, given Randles-Sevcik equation, which demonstrated that the reaction was mainly diffusion controlled. Overall, understanding this complex’s electronic structure and electrochemical behavior can help develop effective catalyts for electrophile cross-coupling reactions and aid in understanding of structure-function relationships.

Synthesis and characterization of (2,2’-Bipyridine) dichloronickel(II) using cyclic voltammetry and nuclear magnetic resonance spectroscopy

ACS Fall 2021

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