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The synthesis of a new homogeneous reductant based on 4,4'- t Bu 2 -2,2'-bipyridine, t Bu-OED 4 , is reported. t Bu-OED 4 was prepared on a multigram scale in two steps from inexpensive and commercially available starting materials, with no chromatography required for purification. t Bu-OED 4 has a reduction potential of -1.33 V (vs Ferrocenium/Ferrocene) and is soluble in a range of common organic solvents. We demonstrate that t Bu-OED 4 can facilitate Ni/Co dual-catalyzed C(sp 2 )-C(sp 3 ) cross-electrophile coupling reactions and is highly functional group tolerant. t Bu-OED 4 is expected to be a valuable addition to the set of homogeneous reductants available for organic transformations., Competing Interests: Competing Financial Interests The authors declare no competing financial interests. Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

A Co II -porphyrin complex (1) with an appended aza-crown ether for Lewis acid (LA) binding was synthesized and characterized. NMR spectroscopy and electrochemistry show that cationic group I and II LAs ( i.e. , Li + , Na + , K + , Ca 2+ , Sr 2+ , and Ba 2+ ) bind to the aza-crown ether group of 1. The binding constant for Li + is comparable to that observed for a free aza-crown ether. LA binding causes an anodic shift in the Co II /Co I couple of between 10 and 40 mV and also impacts the Co III /Co II couple. The magnitude of the anodic shift of the Co II /Co I couple varies linearly with the strength of the LA as determined by the p K a of the corresponding metal-aqua complex, with dications giving larger shifts than monocations. The extent of the anodic shift of the Co II /Co I couple also increases as the ionic strength of the solution decreases. This is consistent with electric field effects being responsible for the changes in the redox properties of 1 upon LA binding and provides a novel method to tune the reduction potential. Density functional theory calculations indicate that the bound LA is 5.6 to 6.8 Å away from the Co II ion, demonstrating that long-range electrostatic effects, which do not involve changes to the primary coordination sphere, are responsible for the variations in redox chemistry. Compound 1 was investigated as a CO 2 reduction electrocatalyst and shows high activity but rapid decomposition., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A general one-pot approach to diverse N-acylsulfenamides from a common S-phenethylsulfenamide starting material is reported. This approach was demonstrated by C-S bond formation utilizing commercially abundant (hetero)aryl iodides and boronic acids to provide sulfilimine intermediates that undergo thermal elimination of styrene. In contrast, all prior approaches to N-acylsulfenamides rely on thiol inputs to introduce sulfenamide S-substituents. A broad scope of reaction inputs was demonstrated including for approved drugs and drug precursors with dense display of functionality. Several different types of sulfur functionalization were performed on a sulfenamide derived from a complex precursor of the blockbuster anticoagulant drug apixaban, highlighting the utility of this approach for the introduction of high oxidation state sulfur groups in complex bioactive compounds. Mechanistic studies established that the key styrene elimination step proceeds by a concerted elimination that does not require reagents or catalysts, and therefore, this one-pot approach should be applicable to the synthesis of N-acylsulfenamides utilizing diverse electrophiles and reaction conditions for C-S bond formation., (© 2023 Wiley-VCH GmbH.)

The insertion of CO 2 into metal alkyl bonds is a crucial elementary step in transition metal-catalyzed processes for CO 2 utilization. Here, we synthesize pincer-supported palladium complexes of the type ( t Bu PBP)Pd(alkyl) ( t Bu PBP = B(NCH 2 P t Bu 2 ) 2 C 6 H 4 - ; alkyl = CH 2 CH 3 , CH 2 CH 2 CH 3, CH 2 C 6 H 5 , and CH 2 -4-OMe-C 6 H 4 ) and ( t Bu PBP)Pd(C 6 H 5 ) and compare the rates of CO 2 insertion into the palladium alkyl bonds to form metal carboxylate complexes. Although, the rate constant for CO 2 insertion into ( t Bu PBP)Pd(CH 2 CH 3 ) is more than double the rate constant we previously measured for insertion into the palladium methyl complex ( t Bu PBP)Pd(CH 3 ), insertion into ( t Bu PBP)Pd(CH 2 CH 2 CH 3 ) occurs approximately one order of magnitude slower than ( t Bu PBP)Pd(CH 3 ). CO 2 insertion into the benzyl complexes ( t Bu PBP)Pd(CH 2 C 6 H 5 ) and ( t Bu PBP)Pd(CH 2 -4-OMe-C 6 H 4 ) is significantly slower than any of the n-alkyl complexes, and CO 2 does not insert into the palladium phenyl bond of ( t Bu PBP)Pd(C 6 H 5 ). While ( t Bu PBP)Pd(CH 2 CH 3 ) and ( t Bu PBP)Pd(CH 2 CH 2 CH 3 ) are resistant to β-hydride elimination, we were unable to synthesize complexes with n -butyl, iso-propyl, and tert -butyl ligands due to β-hydride elimination and an unusual reductive coupling, which involves the formation of new C-B bonds. This reductive process also occurred for ( t Bu PBP)Pd(CH 2 C 6 H 5 ) at elevated temperature and a related process involving the formation of a new H-B bond prevented the isolation of ( t Bu PBP)PdH. DFT calculations provide insight into the relative rates of CO 2 insertion and indicate that steric factors are critical. Overall, this work is one of the first comparative studies of the rates of CO 2 insertion into different metal alkyl bonds and provides fundamental information that may be important for the development of new catalysts for CO 2 utilization., Competing Interests: The authors declare no competing financial interests., (This journal is © The Royal Society of Chemistry.)

The kinetics of hydride transfer from Re( R bpy)(CO) 3 H (bpy = 4,4'-R-2,2'-bipyridine; R = OMe, t Bu, Me, H, Br, COOMe, CF 3 ) to CO 2 and seven different cationic N-heterocycles were determined. Additionally, the thermodynamic hydricities of complexes of the type Re( R bpy)(CO) 3 H were established primarily using computational methods. Linear free-energy relationships (LFERs) derived by correlating thermodynamic and kinetic hydricities indicate that, in general, the rate of hydride transfer increases as the thermodynamic driving force for the reaction increases. Kinetic isotope effects range from inverse for hydride transfer reactions with a small driving force to normal for reactions with a large driving force. Hammett analysis indicates that hydride transfer reactions with greater thermodynamic driving force are less sensitive to changes in the electronic properties of the metal hydride, presumably because there is less buildup of charge in the increasingly early transition state. Bronsted α values were obtained for a range of hydride transfer reactions and along with DFT calculations suggest the reactions are concerted, which enables the use of Marcus theory to analyze hydride transfer reactions involving transition metal hydrides. It is notable, however, that even slight perturbations in the steric properties of the Re hydride or the hydride acceptor result in large deviations in the predicted rate of hydride transfer based on thermodynamic driving forces. This indicates that thermodynamic considerations alone cannot be used to predict the rate of hydride transfer, which has implications for catalyst design.

The insertion of carbon dioxide into metal element σ-bonds is an important elementary step in many catalytic reactions for carbon dioxide valorization. Here, the insertion of carbon dioxide into a family of group 10 alkyl complexes of the type ( R PBP)M(CH 3 ) ( R PBP = B(NCH 2 PR 2 ) 2 C 6 H 4 - ; R = Cy or t Bu; M = Ni or Pd) to generate κ 1 -acetate complexes of the form ( R PBP)M{OC(O)CH 3 } is investigated. This involved the preparation and characterization of a number of new complexes supported by the unusual R PBP ligand, which features a central boryl donor that exerts a strong trans -influence, and the identification of a new decomposition pathway that results in C-B bond formation. In contrast to other group 10 methyl complexes supported by pincer ligands, carbon dioxide insertion into ( R PBP)M(CH 3 ) is facile and occurs at room temperature because of the high trans -influence of the boryl donor. Given the mild conditions for carbon dioxide insertion, we perform a rare kinetic study on carbon dioxide insertion into a late-transition metal alkyl species using ( t Bu PBP)Pd(CH 3 ). These studies demonstrate that the Dimroth-Reichardt parameter for a solvent correlates with the rate of carbon dioxide insertion and that Lewis acids do not promote insertion. DFT calculations indicate that insertion into ( t Bu PBP)M(CH 3 ) (M = Ni or Pd) proceeds via an S E 2 mechanism and we compare the reaction pathway for carbon dioxide insertion into group 10 methyl complexes with insertion into group 10 hydrides. Overall, this work provides fundamental insight that will be valuable for the development of improved and new catalysts for carbon dioxide utilization., Competing Interests: The authors declare no competing financial interests., (This journal is © The Royal Society of Chemistry.)