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1. Activator-free single-component Co( i )-catalysts for regio- and enantioselective heterodimerization and hydroacylation reactions of 1,3-dienes. New reduction procedures for synthesis of [L]Co( i )-complexes and comparison to in situ generated catalysts

   https://doi.org/10.1039/d2dt01484j  

   Parsutkar, Mahesh M.; Moore, Curtis E.; RajanBabu, T. V. (June 2022, Dalton Transactions)

   Warren Piers (Ed.)

   Although cobalt( i ) bis-phosphine complexes have been implicated in many selective C–C bond-forming reactions, until recently relatively few of these compounds have been fully characterized or have been shown to be intermediates in catalytic reactions. In this paper we present a new practical method for the synthesis and isolation of several cobalt( i )-bis-phosphine complexes and their use in Co( i )-catalyzed reactions. We find that easily prepared ( in situ generated or isolated) bis-phosphine and (2,6- N -aryliminoethyl)pyridine (PDI) cobalt( ii ) halide complexes are readily reduced by 1,4-bis-trimethylsilyl-1,4-dihydropyrazine or commercially available lithium nitride (Li 3 N), leaving behind only innocuous volatile byproducts. Depending on the structures of the bis-phosphines, the cobalt( i ) complex crystallizes as a phosphine-bridged species [(P∼P)(X)Co I [μ-(P∼P)]Co I (X)(P∼P)] or a halide-bridged species [(P∼P)Co I [μ-(X)] 2 Co I (P∼P)]. Because the side-products are innocuous, these methods can be used for the in situ generation of catalytically competent Co( i ) complexes for a variety of low-valent cobalt-catalyzed reactions of even sensitive substrates. These complexes are also useful for the synthesis of rare cationic [(P∼P)Co I -η 4 -diene] + X − or [(P∼P)Co I -η 6 -arene] + X − complexes, which are shown to be excellent single-component catalysts for the following regioselective reactions of dienes: heterodimerizations with ethylene or methyl acrylate, hydroacylation and hydroboration. The reactivity of the single-component catalysts with the in situ generated species are also documented. 

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2. Heterogeneous Nature of Electrocatalytic CO/CO ₂ Reduction by Cobalt Phthalocyanines

   https://doi.org/10.1002/cssc.202001396  

   Wu, Yueshen; Hu, Gongfang; Rooney, Conor_L; Brudvig, Gary_W; Wang, Hailiang (July 2020, ChemSusChem)

   Abstract Molecular catalysts for electrochemical CO₂reduction have traditionally been studied in their dissolved states. However, the heterogenization of molecular catalysts has the potential to deliver much higher reaction rates and enable the reduction of CO₂by more than two electrons. In light of the recently discovered reactivity of heterogenized cobalt phthalocyanine molecules to catalyze CO₂reduction into methanol, direct comparison is needed to uncover the distinct catalytic activity and selectivity in homogeneous catalysis versus heterogeneous catalysis. Herein, soluble cobalt phthalocyanine derivatives were synthesized, and their catalytic activities in the homogeneous solutions were evaluated. The results show that the observed catalytic activities for both CO₂‐to‐CO and CO‐to‐methanol conversions in aqueous solutions of the cobalt phthalocyanines are predominantly heterogeneous in nature through the adsorbed species on the electrode. 

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3. Exploring the Surface Chemistry of Cobalt Porphyrin Complexed with Iodine Using Single Molecule Microscopy and Theory

   https://doi.org/10.1021/acs.jpcc.4c08743  

   Kashi, Chiranjeevulu; Nandi, Goutam; Johnson, Kristen N; Sireesha, Pedaballi; Gurdumov, Kirill; Chilukuri, Bhaskar; Hipps, K W; Mazur, Ursula (April 2025, The Journal of Physical Chemistry C)

   Understanding the interactions between molecules on surfaces is crucial for advancing technologies in sensing, catalysis, and energy harvesting. In this study we explore the complex surface chemistry resulting from the interaction of Co(II)octaethylporphyrin (CoOEP) and iodine, I2, both in solution and at the phenyloctane/HOPG interface. In pursuit of this goal, we report results from electrochemistry, NMR and UV-Vis spectroscopy, X-ray crystallography, scanning tunneling microscopy (STM), and density functional theory (DFT). Both spectroscopic methods of analysis confirmed that at and above the stoichiometric ratio of one CoOEP to one I2 the reaction product was metal centered CoIII(OEP)I. X-ray crystallography verified that a single iodine is bonded to each cobalt ion in the triclinic, P-1 system. The surface chemistry of CoOEP and I2 is complicated and remarkably dependent on the iodine concentration. STM images of CoOEP and I2 in phenyloctane on highly oriented pyrolytic graphite (HOPG) at low halogen concentrations (1:<2 Co:I ratios) presented random individual Co(OEP)I molecules weakly adsorbed onto a hexagonal (HEX) CoOEP monolayer. Images of 1:2 Co:I ratio solutions, showed phase segregated HEX CoOEP and pseudo-rectangular (REC) Co(OEP)I incorporating one solvent molecule per Co(OEP)I. The REC structure formed in long parallel rows with the number of rows increasing with increasing solution I2. In this case, the presence of CoOEP on the surface was attributed to the spontaneous reduction of Co(OEP)I by the graphite substrate. DFT calculations indicate that the REC Co(OEP)I:PhO form is energetically more stable than the HEX form of Co(OEP)I on HOPG. Experimental STM images and DFT calculated adsorption energies and STM images support our interpretation of the observed structures. 

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4. Bimetallic, Silylene‐Mediated Multielectron Reductions of Carbon Dioxide and Ethylene

   https://doi.org/10.1002/anie.202011489  

   Whited, Matthew T.; Zhang, Jia; Conley, Anna M.; Ma, Senjie; Janzen, Daron E.; Kohen, Daniela (November 2020, Angewandte Chemie International Edition)

   Abstract A metal/ligand cooperative approach to the reduction of small molecules by metal silylene complexes (R₂Si=M) is demonstrated, whereby silicon activates the incoming substrate and mediates net two‐electron transformations by one‐electron redox processes at two metal centers. An appropriately tuned cationic pincer cobalt(I) complex, featuring a central silylene donor, reacts with CO₂to afford a bimetallic siloxane, featuring two Co^IIcenters, with liberation of CO; reaction of the silylene complex with ethylene yields a similar bimetallic product with an ethylene bridge. Experimental and computational studies suggest a plausible mechanism proceeding by [2+2] cycloaddition to the silylene complex, which is quite sensitive to the steric environment. The Co^II/Co^IIproducts are reactive to oxidation and reduction. Taken together, these findings demonstrate a strategy for metal/ligand cooperative small‐molecule activation that is well‐suited to 3dmetals. 

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5. Atom-by-atom electrodeposition of single isolated cobalt oxide molecules and clusters for studying the oxygen evolution reaction

   https://doi.org/10.1073/pnas.2002168117  

   Jin, Zhaoyu; Bard, Allen J. (May 2020, Proceedings of the National Academy of Sciences)

   We report an electrodeposition protocol for preparing isolated cobalt oxide single molecules (Co₁O_x) and clusters (Co_nO_y) on a carbon fiber nanoelectrode. The as-prepared deposits are able to produce well-defined steady-state voltammograms for the oxygen evolution reaction (OER) in alkaline media, where the equivalent radius (r_d) is estimated by the limiting current of hydroxide oxidation in accordance with the electrocatalytic amplification model. The size of isolated clusters obtained from the femtomolar Co²⁺solution through an atom-by-atom technique can reach as small as 0.21 nm (r_d) which is approximately the length of Co–O bond in cobalt oxide. Therefore, the deposit was close to that of a Co₁O_xsingle molecule with only one cobalt ion, the minimum unit of the cobalt-based oxygen-evolving catalyst. Additionally, the size-dependent catalysis of the OER on Co_nO_ydeposits shows a faster relative rate on the smaller cluster in terms of the potential at a given current density, implying the single molecular catalyst shows a superior OER activity. 

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