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1. Carbonyl and ester C–O bond hydrosilylation using κ ⁴ -diimine nickel catalysts

   https://doi.org/10.1039/C8DT01857J  

   Rock, Christopher L.; Groy, Thomas L.; Trovitch, Ryan J. (January 2018, Dalton Transactions)

   The synthesis of alkylphosphine-substituted α-diimine (DI) ligands and their subsequent addition to Ni(COD) 2 allowed for the preparation of ( iPr2PPr DI)Ni and ( tBu2PPr DI)Ni . The solid state structures of both compounds were found to feature a distorted tetrahedral geometry that is largely consistent with the reported structure of the diphenylphosphine-substituted variant, ( Ph2PPr DI)Ni . To explore and optimize the synthetic utility of this catalyst class, all three compounds were screened for benzaldehyde hydrosilylation activity at 1.0 mol% loading over 3 h at 25 °C. Notably, ( Ph2PPr DI)Ni was found to be the most efficient catalyst while phenyl silane was the most effective reductant. A broad scope of aldehydes and ketones were then hydrosilylated, and the silyl ether products were hydrolyzed to afford alcohols in good yield. When attempts were made to explore ester reduction, inefficient dihydrosilylation was noted for ethyl acetate and no reaction was observed for several additional substrates. However, when an equimolar solution of allyl acetate and phenyl silane was added to 1.0 mol% ( Ph2PPr DI)Ni , complete ester C–O bond hydrosilylation was observed within 30 min at 25 °C to generate propylene and PhSi(OAc) 3 . The scope of this reaction was expanded to include six additional allyl esters, and under neat conditions, turnover frequencies of up to 990 h −1 were achieved. This activity is believed to be the highest reported for transition metal-catalyzed ester C–O bond hydrosilylation. Proposed mechanisms for ( Ph2PPr DI)Ni -mediated carbonyl and allyl ester C–O bond hydrosilylation are also discussed. 

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2. Uncovering a superfamily of nickel‑dependent hydroxyacid racemases and epimerases

   https://doi.org/10.1038/s41598-020-74802-6  

   Desguin, Benoît; Urdiain‑ Arraiza, Julian; Da Costa, Matthieu; Fellner, Matthias; Hu, Jian; Hausinger, Robert P.; Desmet, Tom; Hols, Pascal; Soumillion, Patrice (October 2020, Scientific reports)

   null (Ed.)

   Isomerization reactions are fundamental in biology. Lactate racemase, which isomerizes L- and D-lactate, is composed of the LarA protein and a nickel-containing cofactor, the nickel-pincer nucleotide (NPN). In this study, we show that LarA is part of a superfamily containing many different enzymes. We overexpressed and purified 13 lactate racemase homologs, incorporated the NPN cofactor, and assayed the isomerization of different substrates guided by gene context analysis. We discovered two malate racemases, one phenyllactate racemase, one α-hydroxyglutarate racemase, two D-gluconate 2-epimerases, and one short-chain aliphatic α-hydroxyacid racemase among the tested enzymes. We solved the structure of a malate racemase apoprotein and used it, along with the previously described structures of lactate racemase holoprotein and D-gluconate epimerase apoprotein, to identify key residues involved in substrate binding. This study demonstrates that the NPN cofactor is used by a diverse superfamily of α-hydroxyacid racemases and epimerases, widely expanding the scope of NPN-dependent enzymes. 

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3. Nickel-catalyzed reductive coupling of unactivated alkyl bromides and aliphatic aldehydes

   https://doi.org/10.1039/d1sc03712a  

   Cruz, Cole L.; Montgomery, John (September 2021, Chemical Science)

   A mild, convenient coupling of aliphatic aldehydes and unactivated alkyl bromides has been developed. The catalytic system features the use of a common Ni( ii ) precatalyst and a readily available bioxazoline ligand and affords silyl-protected secondary alcohols. The reaction is operationally simple, utilizing Mn as a stoichiometric reductant, and tolerates a wide range of functional groups. The use of 1,5-hexadiene as an additive is an important reaction parameter that provides significant benefits in yield optimizations. Initial mechanistic experiments support a mechanism featuring an alpha-silyloxy Ni species that undergoes formal oxidative addition to the alkyl bromide via a reductive cross-coupling pathway. 

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4. Nickel telluride as a bifunctional electrocatalyst for efficient water splitting in alkaline medium

   https://doi.org/10.1039/c8ta01760c  

   De Silva, Umanga; Masud, Jahangir; Zhang, Ning; Hong, Yu; Liyanage, Wipula P.; Asle Zaeem, Mohsen; Nath, Manashi (January 2018, Journal of Materials Chemistry A)

   Designing efficient electrocatalysts has been one of the primary goals for water electrolysis, which is one of the most promising routes towards sustainable energy generation from renewable sources. In this article, we have tried to expand the family of transition metal chalcogenide based highly efficient OER electrocatalysts by investigating nickel telluride, Ni 3 Te 2 as a catalyst for the first time. Interestingly Ni 3 Te 2 electrodeposited on a GC electrode showed very low onset potential and overpotential at 10 mA cm −2 (180 mV), which is the lowest in the series of chalcogenides with similar stoichiometry, Ni 3 E 2 (E = S, Se, Te) as well as Ni-oxides. This observation falls in line with the hypothesis that increasing the covalency around the transition metal center enhances catalytic activity. Such a hypothesis has been previously validated in oxide-based electrocatalysts by creating anion vacancies. However, this is the first instance where this hypothesis has been convincingly validated in the chalcogenide series. The operational stability of the Ni 3 Te 2 electrocatalyst surface during the OER for an extended period of time in alkaline medium was confirmed through surface-sensitive analytical techniques such as XPS, as well as electrochemical methods which showed that the telluride surface did not undergo any corrosion, degradation, or compositional change. More importantly we have compared the catalyst activation step (Ni 2+ → Ni 3+ oxidation) in the chalcogenide series, through electrochemical cyclic voltammetry studies, and have shown that catalyst activation occurs at lower applied potential as the electronegativity of the anion decreases. From DFT calculations we have also shown that the hydroxyl attachment energy is more favorable on the Ni 3 Te 2 surface compared to the Ni-oxide, confirming the enhanced catalytic activity of the telluride. Ni 3 Te 2 also exhibited efficient HER catalytic activity in alkaline medium making it a very effective bifunctional catalyst for full water splitting with a cell voltage of 1.66 V at 10 mA cm −2 . It should be noted here that this is the first report of OER and HER activity in the family of Ni-tellurides. 

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5. Three-Component Ni-Catalyzed Silylacylation of Alkenes

   https://doi.org/10.1021/acscatal.0c05449  

   Ni, Dongshun; Brown, M. Kevin (January 2021, ACS Catalysis)

   null (Ed.)

   A Ni-catalyzed silylacylation of alkenes is presented. The reaction combines alkenes, ClZnSiR3, and acid chlorides to provide rapid access to β-silyl ketones. Importantly, the method involves a [Ni]-SiR3 complex as a catalytic intermediate, which is rarely described for three-component alkene functionalization. Finally, the synthetic utility of the products is demonstrated, and the mechanistic details are described. 

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