In the past decade, palladium-catalyzed C-H activation/C-C bond forming reactions have emerged as promising new catalytic transformations; however, development in this field is still at an early stage compared to the state of the art in cross-coupling reactions using aryl and alkyl halides. This Review begins with a brief introduction of four extensively investigated modes of catalysis for forming C-C bonds from C-H bonds: Pd(II)/Pd(0), Pd(II)/Pd(IV), Pd(0)/Pd(II)/Pd(IV) and Pd(0)/ Pd(II) catalysis. More detailed discussion is then directed towards the recent development of Pd(II)-catalyzed coupling of C-H bonds with organometallic reagents through a Pd(II)/Pd(0) catalytic cycle. Despite much progress made to date, improving the versatility and practicality of this new reaction remains a tremendous challenge.

Palladium-catalyzed alkylations of sp2 and sp3 C-H bonds with either methylboroxine or alkylboronic acids were developed. Ag2O or AgCO3 is used as a crucial oxidant and promoter for the transmetalation step. Ether, ester, alcohol, and alkene functional groups are tolerated. A new C-H activation pathway differing from the cyclometalation process is elucidated using methylboroxine as the coupling partner.

The catalytic activation of C(sp 3 )ÀH and C(sp 2 )ÀH bonds in readily available, inexpensive starting materials would provide a valuable array of new transformations for organic chemistry research and the fine chemical industry.[1] Activation of C(sp 2 )ÀH bonds in benzene and ortho-substituted arenes has been successfully exploited in the development of catalytic CÀC bond-forming reactions by coupling to olefins. [2,3] The selective activation of C(sp 3 )ÀH bonds under mild conditions could be an attractive strategy for the development of catalytic reactions with wide applicability. Despite extensive efforts that have focused mainly on carbene and nitrene insertions, metathesis, Shilov chemistry, and biomimetic approaches, the catalytic and asymmetric functionalization of C(sp 3 )ÀH bonds remains a significant challenge.[4]We report herein an auxiliary approach for the chemoselective and asymmetric room-temperature iodination of

Lithium–sulfur (Li–S) batteries have extremely high theoretical energy density that make them as promising systems toward vast practical applications. Expediting redox kinetics of sulfur species is a decisive task to break the kinetic limitation of insulating lithium sulfide/disulfide precipitation/dissolution. Herein, we proposed a porphyrin‐derived atomic electrocatalyst to exert atomic‐efficient electrocatalytic effects on polysulfide intermediates. Quantifying electrocatalytic efficiency of liquid/solid conversion through a potentiostatic intermittent titration technique measurement presents a kinetic understanding of specific phase evolutions imparted by the atomic electrocatalyst. Benefiting from atomically dispersed “lithiophilic” and “sulfiphilic” sites on conductive substrates, the finely designed atomic electrocatalyst endows Li–S cells with remarkable cycling stablity (cyclic decay rate of 0.10% in 300 cycles), excellent rate capability (1035 mAh g−1 at 2 C), and impressive areal capacity (10.9 mAh cm−2 at a sulfur loading of 11.3 mg cm−2). The present work expands atomic electrocatalysts to the Li–S chemistry, deepens kinetic understanding of sulfur species evolution, and encourages application of emerging electrocatalysis in other multielectron/multiphase reaction energy systems.

Unactivated CH3 groups in 2‐oxazolines are oxidized by inexpensive oxidants, such as tert‐butyl peroxyacetate and lauroyl peroxide, in the presence of a catalytic amount of Pd(OAc)2. Carboxylic anhydrides are essential for both the oxidation of the PdC bonds and regeneration of Pd(OAc)2. The use of [D6]Ac2O as the solvent shows that the acetyl group incorporated into the product is from acetic anhydride rather than the oxidant (see scheme).

We study the preparation and capping of silver nanoparticles by several unsaturated long-chain carboxylates. UV-visible and FTIR spectroscopy and high-resolution electron microscopy are used to characterize the effect of the chain length, its configuration, and the degree of unsaturation on the size distribution of the nanoparticles. Langmuir layers and Langmuir-Blodgett films are used to study the adsorption of these carboxylates on the particles. We find that unsaturated carboxylates in the cis configuration are useful stabilizers for the control of particle size and its surface properties.

Lean-electrolyte conditions are highly pursued for practical lithium (Li) metal batteries. The previous studies on the Li metal anodes, in general, exhibited good stability with a large excess of electrolyte. However, the targeted design of Li hosts under relatively low electrolyte conditions has been rarely studied so far. Herein, we have shown that electrolyte consumption severely affects the cycling stability of Li metal anode. Considering carbon hosts as typical examples, we innovatively employed in situ synchrotron X-ray diffraction, in situ Raman spectroscopy, and theoretical computations to obtain a better understanding of the Li nucleation/deposition processes. We also showed the usefulness of in situ electrochemical impedance spectra to analyze interfacial fluctuation at the Li/electrolyte interface, together with nuclear magnetic resonance data to quantify electrolyte consumption. We have found that uneven Li nucleation/deposition and the crack of surface-area-derived solid-electrolyte interface (SEI) layer both lead to a great consumption of electrolyte. Then, we suggested a design principle for Li host to overcome the electrolyte loss, that is, uneven growth of the Li structure and the crack of the SEI layer must be simultaneously controlled. As a proof of concept, we demonstrated the usefulness of a 3D low-surface-area defective graphene host (L-DG) to control Li nucleation/deposition and stabilize the SEI layer, contributing to a highly reversible Li plating/ stripping. As a result, such a Li host can achieve stable cycles (e.g., 1.0 mAh cm −2 ) with a low electrolyte loading (10 μL). This work demonstrates the necessity to design Li metal anodes under lean-electrolyte conditions and brings Li metal batteries a step closer to their practical applications.

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