Electrochemistry and Adsorption of Bis 2,2′‐Bipyridinecobalt(I) and Bis 6,6′‐Dimethyl‐2,2′‐Bipyridinecobalt(I) in Acetonitrile

Abstract

Cyclic voltammetry, coulometry, and chronocoulometry were used to examine the reduction of bis-2,2'-bipyridinecobalt(TI), Co(bipy)22+, and bis-6,6'-dimethyl-2,2'-bipyridinecobalt(II),Both of the cobalt(I) reduction products, Co(bipy)2 + and Co(dmbp) +, adsorb on mercury but not on graphite or platinum electrodes. Co(bipy) + decomposes at a modest rate while Co(dmbp)2 + is much more stable. Neither reduced complex proved effective as a catalyst for the electroreduction of nitrous oxide or alkyl halides.

Cobalt-Catalyzed C(sp2)–CN Bond Activation: Cross-Electrophile Coupling for Biaryl Formation and Mechanistic Insight

“…A close look at characteristic bond distances (see Table S9) and comparison with literature values validated the 3/1 ratio found and indicated a charge repartition mainly centered on the metallic atoms in the solid state of Co I (Bipy 0 ) 3 (see S6 for full details on X-ray structure solving) . Moreover, the X-ray structure of Co-Red is consistent with the observation by Willett and Anson that Co I complexes of less than three 2,2′-bipyridines per cobalt have high propensity to redistribute their ligands to fill their coordination sites in order to gain stability. Because the ligand redistribution is believed to generate cobalt(0), , this led us to propose the following equation for the formation of Co-Red (Chart ).…”

“…Moreover, the X-ray structure of Co-Red is consistent with the observation by Willett and Anson that Co I complexes of less than three 2,2′-bipyridines per cobalt have high propensity to redistribute their ligands to fill their coordination sites in order to gain stability. Because the ligand redistribution is believed to generate cobalt(0), , this led us to propose the following equation for the formation of Co-Red (Chart ). Besides, this result points out the importance of having investigated the nature of the catalysis.…”

“…The cyclic voltammogram of A revealed a 2-electron reduction wave at E ° = −1.55 V versus SCE, which corresponds to the Co I /Co –I couple. The partially reversible 1-electron wave at E p ox = −0.86 V versus SCE can be assigned to the oxidation of Co I into Co II species . By comparison, the cyclic voltammogram of B disclosed a slower electron transfer, presenting also a 2-electron reduction wave, but at E ° = −1.58 V versus SCE.…”

Metal–Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations

“…The steric protection around the Co center in ( Ar PDI)­Co­(N 2 ) is key to stabilizing the reduced Co compound from undergoing intermolecular decomposition. Co­( Me2 bpy) 2 showed broad UV–vis peaks in THF at 635 and 688 nm, indicating a strong metal-to-ligand charge-transfer (MLCT) transition in this low valence Co species . However, Co­( Me2 bpy) 2 is EPR silent even at 77 K, possibly due to rapid relaxation processes.…”

Dechlorination of β-methylallyl chloride by electrogenerated [Co(I)(bipyridine)3]+: An electrochemical study in the presence of cationic surfactants

“…In the reverse scan there are two anodic peaks at −1120 and −1070 mV (SCE) with an inverted peak in between them. The observed complicated redox behavior of [Co(II)(bpy) 3 ] 2+ in 0.1 M NaBr may be due to several processes, such as adsorption of the Co(II) complex, low solubility of the product formed at the cathodic peak, viz., [Co(I)(bpy) 3 ] + [24], and decomposition of the Co(I) complex in aqueous solution to a bis form [Co(I)(bpy) 2 ] + and the free ligand [25,26]. Curve crossing of CV traces between the forward and reverse scans (curve (a)) indeed signifies possibilities for a series of chemical reactions occurring within the electrochemical time scales of the CV scan [27][28][29].…”