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Despite recent advances in cluster-based catalysis for organic synthesis, the substrate scope of reactions catalyzed by metal nanoclusters is typically not superior to previously established catalytic systems. Herein, we develop new atomically precise copper nanoclusters for protosilylation, with scope expanding to alkenes and simple enynes that were not suitable for prior synthetic methodologies with traditional copper complexes. The involvement of a second copper center in the metal kernel during the migratory insertion step is thought to be responsible for the expanded scope. In addition, the reaction is highly compatible with water and can be carried out in open air rather than under inert gas protection. Mechanistic studies suggest that the cluster-catalyzed protosilylation proceeds in the absence of silyl radicals. The current findings demonstrate the potential of using metal nanoclusters for practical and sustainable chemical synthesis., (© 2024 Wiley-VCH GmbH.)

Pd(II)-catalyzed enantioselective C-H activation has emerged as a versatile platform for constructing point, axial, and planar chirality. Herein, we present an unexpected discovery of a Pd-catalyzed enantioselective cascade β,γ-methylene C(sp 3 )-H diarylation of free carboxylic acids using bidentate chiral mono-protected amino thioether ligands (MPAThio), enabling one-step synthesis of a complex chiral 9,10-dihydrophenanthrene scaffolds with high enantioselectivity. In this process, two methylene C(sp 3 )-H bonds and three C(sp 2 )-H bonds were activated, leading to the formation of four C-C bonds and three chiral centers in one pot. A plausible catalytic pathway starts with enantioselective β,γ-dehydrogenation to form chiral β,γ-cyclohexene. Intriguingly, this olefin serves as a norbornene-type reagent (presumably assisted by the carboxyl directing effect), relaying two successive Catellani arylation reactions and a C-H arylation reaction to furnish chiral 9,10-dihydrophenanthrenes along with meta-selective homocoupling products of iodoarene., (© 2024 Wiley-VCH GmbH.)

Electron-rich phosphines play a crucial role in transition metal-based homogeneous catalysis. While alkyl groups have traditionally been employed to increase the phosphine donor strength, recent studies have shown that zwitterionic functional groups such as phosphorus ylides can result in a further enhancement. Herein we report the concept of twisting a C=C double bond to introduce a zwitterionic substituent by the synthesis and application of N-heterocyclic olefin phosphines with a sulfonyl substituent (sNHOP). This sulfonyl group enables the twisting of the olefin moiety due to steric and electronic stabilization of the carbanionic center. The resulting zwitterionic structure leads to a significant increase of the donor strength of the sNHOP ligands compared to conventional NHOP systems with a planar N-heterocyclic olefin moiety. The potential of this new ligand platform for catalysis is demonstrated by its application in the gold-catalyzed hydroamination and cyclo-isomerization of alkynes. Here, the ligands outperform the original NHOP ligands suggesting favorable properties for future catalysis applications., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

A three-component coupling approach toward structurally complex dialkylsulfides is described via the nickel-catalyzed 1,2-carbosulfenylation of unactivated alkenes with organoboron nucleophiles and alkylsulfenamide (N-S) electrophiles. Efficient catalytic turnover is facilitated using a tailored N-S electrophile containing an N-methyl methanesulfonamide leaving group, allowing catalyst loadings as low as 1 mol %. Regioselectivity is controlled by a collection of monodentate, weakly coordinating native directing groups, including sulfonamides, amides, sulfinamides, phosphoramides, and carbamates. Key to the development of this transformation is the identification of quinones as a family of hemilabile and redox-active ligands that tune the steric and electronic properties of the metal throughout the catalytic cycle. Density functional theory (DFT) results show that the duroquinone (DQ) ligand adopts different coordination modes in different stages of the Ni-catalyzed 1,2-carbosulfenylation-binding as an η 6 capping ligand to stabilize the precatalyst/resting state and prevent catalyst decomposition, binding as an X-type redox-active durosemiquinone radical anion to promote alkene migratory insertion with a less distorted square planar Ni(II) center, and binding as an L-type ligand to promote N-S oxidative addition at a relatively more electron-rich Ni(I) center., (© 2024 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Alkyl chlorides are a class of versatile building blocks widely used to generate C(sp 3 )-rich scaffolds through transformation such as nucleophilic substitution, radical addition reactions and metal-catalyzed cross-coupling processes. Despite their utility in the synthesis of high-value functional molecules, distinct methods for the preparation of alkyl chlorides are underrepresented. Here, we report a visible-light-mediated dual catalysis strategy for the modular synthesis of highly functionalized and structurally diverse arylated chloroalkanes via the coupling of diaryliodonium salts, alkenes and potassium chloride. A distinctive aspect of this transformation is a ligand-design-driven approach for the development of a copper(II)-based atom-transfer catalyst that enables the aryl-chlorination of electron-poor alkenes, complementing its iron(III)-based counterpart that accommodates non-activated aliphatic alkenes and styrene derivatives. The complementarity of the two dual catalytic systems allows the efficient aryl-chlorination of alkenes bearing different stereo-electronic properties and a broad range of functional groups, maximizing the structural diversity of the 1-aryl, 2-chloroalkane products., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Alternating current (AC) and pulsed electrolysis are gaining traction in electro(organic) synthesis due to their advantageous characteristics. We employed AC electrolysis in electrochemically mediated Atom Transfer Radical Polymerization (eATRP) to facilitate the regeneration of the activator Cu I complex on Cu 0 electrodes. Additionally, Cu 0 served as a slow supplemental activator and reducing agent (SARA ATRP), enabling the activation of alkyl halides and the regeneration of the Cu I activator through a comproportionation reaction. We harnessed the distinct properties of Cu 0 dual regeneration, both chemical and electrochemical, by employing sinusoidal, triangular, and square-wave AC electrolysis alongside some of the most active ATRP catalysts available. Compared to linear waveform (DC electrolysis) or SARA ATRP (without electrolysis), pulsed and AC electrolysis facilitated slightly faster and more controlled polymerizations of acrylates. The same AC electrolysis conditions could successfully polymerize eleven different monomers across different mediums, from water to bulk. Moreover, it proved effective across a spectrum of catalyst activity, from low-activity Cu/2,2-bipyridine to highly active Cu complexes with substituted tripodal amine ligands. Chain extension experiments confirmed the high chain-end fidelity of the produced polymers, yielding functional and high molecular-weight block copolymers. SEM analysis indicated the robustness of the Cu 0 electrodes, sustaining at least 15 consecutive polymerizations., (© 2024 Wiley-VCH GmbH.)

Herein, multiple types of chiral Os(II) complexes have been designed to address the appealing yet challenging asymmetric C(sp 3 )-H functionalization, among which the Os(II)/Salox species is found to be the most efficient for precise stereocontrol in realizing the asymmetric C(sp 3 )-H amidation. As exemplified by the enantioenriched pyrrolidinone synthesis, such tailored Os(II)/Salox catalyst efficiently enables an intramolecular site-/enantioselective C(sp 3 )-H amidation in the γ-position of dioxazolone substrates, in which benzyl, propargyl and allyl groups bearing various substituted forms are well compatible, affording the corresponding chiral γ-lactam products with good er values (up to 99 : 1) and diverse functionality (>35 examples). The unique performance advantage of the developed chiral Os(II)/Salox system in terms of the catalytic energy profile and the chiral induction has been further clarified by integrated experimental and computational studies., (© 2024 Wiley-VCH GmbH.)

We disclose the development of a Cu-catalyzed C-O coupling method utilizing a new N 1 ,N 2 -diarylbenzene-1,2-diamine ligand, L8. Under optimized reaction conditions, structurally diverse aryl and heteroaryl bromides underwent efficient coupling with a variety of alcohols at room temperature using an L8-based catalyst. Notably, the L8-derived catalyst exhibited enhanced activity when compared to the L4-based system previously disclosed for C-N coupling, namely the ability to functionalize aryl bromides containing acidic functional groups. Mechanistic studies demonstrate that C-O coupling utilizing L8 ⋅ Cu involves rate-limiting alkoxide transmetallation, resulting in a mechanism of C-O bond formation that is distinct from previously described Pd-, Cu-, or Ni-based systems. This lower energy pathway leads to rapid C-O bond formation; a 7-fold increase relative to what is seen with other ligands. The results presented in this report overcome limitations in previously described C-O coupling methods and introduce a new ligand that we anticipate may be useful in other Cu-catalyzed C-heteroatom bond-forming reactions., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

We report the room temperature dimerization of carbon monoxide mediated by C4/C5-vicinal anionic dicarbenes Li(ADC) (ADC = ArC{(Dipp)NC} 2 ; Dipp = 2,6-iPr 2 C 6 H 3 ; Ar = Ph, DMP (4-Me 2 NC 6 H 4 ), Bp (4-PhC 6 H 4 )) to yield (E)-ethene-1,2-bis(olate) (i.e. - O-C=C-O - = CO en ) bridged mesoionic carbene (iMIC) lithium compounds CO en -[(iMIC)Li] 2 (CO en -[iMIC] 2 = [ArC{(Dipp)NC} 2 (CO)] 2 ) in quantitative yields. CO en -[(iMIC)Li] 2 are highly colored stable solids, exhibit a strikingly small HOMO-LUMO energy gap, and readily undergo 2e-oxidations with selenium, CuCl (or CuCl 2 ), and AgCl to afford the dinuclear compounds CO on -[(iMIC)E] 2 (E = Se, CuCl, AgCl) featuring a 1,2-dione bridged neutral bis-iMIC (i.e. CO on -[iMIC] 2 = [ArC{(Dipp)NC} 2 (C=O)] 2 ). CO en -[(iMIC)Li] 2 undergo redox-neutral salt metathesis reactions with LiAlH 4 and (Et 2 O) 2 BeBr 2 and afford CO en -[(iMIC)AlH 2 ] 2 and CO en -[(iMIC)BeBr] 2 , in which the dianionic CO en -moiety remains intact. All compounds have been characterized by NMR spectroscopy, mass spectrometry, and X-ray diffraction. Stereoelectronic properties of CO on -[iMIC] 2 are quantified by experimental and theoretical methods., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

IMes (IMes=1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) and IPr (IPr=1,3- bis(2,6-diisopropylphenyl)imidazol-2-ylidene) represent by far the most frequently used N-heterocyclic carbene ligands in homogeneous catalysis, however, despite numerous advantages, these ligands are limited by the lack of steric flexibility of catalytic pockets. We report a new class of unique unsymmetrical N-heterocyclic carbene ligands that are characterized by freely-rotatable N-aromatic wingtips in the imidazol-2-ylidene architecture. The combination of rotatable N-CH 2 Ar bond with conformationally-fixed N-Ar linkage results in a highly modular ligand topology, entering the range of geometries inaccessible to IMes and IPr. These ligands are highly reactive in Cu(I)-catalyzed β-hydroboration, an archetypal borylcupration process that has had a transformative impact on the synthesis of boron-containing compounds. The most reactive Cu(I)-NHC in this class has been commercialized in collaboration with MilliporeSigma to enable broad access of the synthetic chemistry community. The ligands gradually cover %V bur geometries ranging from 37.3 % to 52.7 %, with the latter representing the largest %V bur described for an IPr analogue, while retaining full flexibility of N-wingtip. Considering the modular access to novel geometrical space in N-heterocyclic carbene catalysis, we anticipate that this concept will enable new opportunities in organic synthesis, drug discovery and stabilization of reactive metal centers., (© 2023 Wiley-VCH GmbH.)

Aromatic amines are ubiquitous moieties in organic molecules and their direct functionalization is of great interest in many research areas due to their prevalence in pharmaceuticals and organic electronics. While several synthetic tools exist for the ortho- and para-functionalization of anilines, the functionalization of the less reactive meta-position is not easy to achieve with current methods. To date, the meta-C-H arylation of aniline derivatives has been restricted to either the use of directing groups & templates, or their transformation into anilides & quaternary anilinium salts. Herein, we report the first general and efficient meta-C-H-arylation of non-directed aniline derivatives via cooperative catalysis with a palladium-S,O-ligand-norbornene system. The reaction proceeds under mild conditions with a wide range of aniline derivatives and aryl iodides, while being operationally simple and scalable. Our preliminary mechanistic investigation-including the isolation of several palladium complexes and deuterium experiments-reveal useful insights into the substituent-effects of both the aniline-substrate and the norbornene-mediator during the meta-C-H activation step., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

While still rare, cationic ligands offer much promise as tunable electron-withdrawing ligands for π-acid catalysis. Recently, we introduced pincer-type sulfonium cations into the list of available strongly π-acidic ancillary ligands. However, the M-S bond in sulfonium complexes of these ligands was found highly labile, precluding their catalytic applications. Herein we demonstrate that this obstacle can be overcome by increasing the rigidity of the sulfonium pincer scaffold. X-ray analyses confirm that despite bearing a formal positive charge, the sulfur atom of this newly designed sulfonium ligand maintains its coordination to the Pt(II)-center, while DFT calculations indicate that by doing so it strongly enhances the electrophilic character of the metal. Kinetic studies carried out on three model cycloisomerization reactions prove that such a tris-cationic sulfonium-Pt(II) complex is highly reactive, compared to its thioether-based analogue. This proof-of-concept study presents the first example of employing sulfonium-based ligands in homogeneous catalysis., (© 2023 Wiley-VCH GmbH.)

Herein, a copper(I)-catalyzed asymmetric hydrophosphination of 3,3-disubstituted cyclopropenes is reported. It provides a series of phosphine derivatives in high to excellent diastereo- and enantioselectivities. The methodology enjoys broad substrate scope on both 3,3-disubstituted cyclopropenes and diarylphosphines. The high stereoselectivity is attributed to both the high stability of the Cu(I)-(R,R)-QUINOXP* complex in the presence of stoichiometric HPPh 2 and the produced phosphines, and the high-performance asymmetric induction of the Cu(I)-(R,R)-QUINOXP* complex. Finally, the method is used for the synthesis of new chiral phosphine-olefin compounds built on a cyclopropane skeleton, one of which serves as a wonderful ligand in Rh-catalyzed asymmetric conjugate addition of phenylboronic acid to various α,β-unsaturated compounds., (© 2023 Wiley-VCH GmbH.)

The study of the redox chemistry of mid-actinides (U-Pu) has historically relied on cerium as a model, due to the accessibility of trivalent and tetravalent oxidation states for these ions. Recently, dramatic shifts of lanthanide 4+/3+ non-aqueous redox couples have been established within a homoleptic imidophosphorane ligand framework. Herein we extend the chemistry of the imidophosphorane ligand (NPC=[N=P t Bu(pyrr) 2 ] - ; pyrr=pyrrolidinyl) to tetrahomoleptic NPC complexes of neptunium and cerium (1-M, 2-M, M=Np, Ce) and present comparative structural, electrochemical, and theoretical studies of these complexes. Large cathodic shifts in the M 4+/3+ (M=Ce, U, Np) couples underpin the stabilization of higher metal oxidation states owing to the strongly donating nature of the NPC ligands, providing access to the U 5+/4+ , U 6+/5+ , and to an unprecedented, well-behaved Np 5+/4+ redox couple. The differences in the chemical redox properties of the U vs. Ce and Np complexes are rationalized based on their redox potentials, degree of structural rearrangement upon reduction/oxidation, relative molecular orbital energies, and orbital composition analyses employing density functional theory., (© 2023 Wiley-VCH Verlag GmbH.)

The reactivity of metal-hydride complexes can be harnessed by the modification of ancillary ligands. With the aim of improving the hydride-donor ability of the key Mn-H intermediate and reducing steric hindrance, we herein report the rational design of a versatile and efficient NHC-based NNC-pincer Mn catalyst for hydrogenation reactions. This newly developed catalyst exhibited higher activity than the corresponding NNP-pincer Mn catalyst owing to its reduced steric hindrance and enhanced Mn-H σ-bonding orbital energy level through a π-antibonding interaction. Using this highly active NNC-pincer Mn catalyst, a rich array of polar unsaturated compounds (>80 examples) including esters, N-heteroarenes, amides, carbonates, and urea derivatives, were successfully hydrogenated under relatively mild conditions. This work represents a rare example of a general phosphine-free Mn-catalyzed hydrogenation system., (© 2023 Wiley-VCH GmbH.)

Amide is one of the most widespread functional groups in organic and bioorganic chemistry, and it would be valuable to achieve stereoselective C(sp 3 )-H functionalization in amide molecules. Palladium(II) catalysis has been prevalently used in the C-H activation chemistry in the past decades, however, due to the weakly-coordinating feature of simple amides, it is challenging to achieve their direct C(sp 3 )-H functionalization with enantiocontrol by Pd II catalysis. Our group has developed sulfoxide-2-hydroxypridine (SOHP) ligands, which exhibited remarkable activity in Pd-catalyzed C(sp 2 )-H activation. In this work, we demonstrate that chiral SOHP ligands served as an ideal solution to enantioselective C(sp 3 )-H activation in simple amides. Herein, we report an efficient asymmetric Pd II /SOHP-catalyzed β-C(sp 3 )-H arylation of aliphatic tertiary amides, in which the SOHP ligand plays a key role in the stereoselective C-H deprotonation-metalation step., (© 2023 Wiley-VCH GmbH.)

The syntheses of the first B9-connected carboranylphosphines (B9-Phos) featuring two carboranyl moieties as well as access to B9-Phos ligands with bulky electron-donating substituents, previously deemed unattainable, is reported. The electrochemical properties of the B9-Phos ligands were investigated, revealing the ability of the mesityl derivatives to form stabilized phosphoniumyl radical cations. The B9-Phos ligands display an extremely electron-releasing character surpassing that of alkyl phosphines and commonly used N-heterocyclic carbenes. This is demonstrated by their very small Tolman electronic parameters (TEPs) as well as extremely low P-Se coupling constants. Cone angles and buried volumes attest to the high steric demand exerted by the (di)carboranyl phosphines. The dicarboranyl phosphine Au I complexes show superior catalytic performance in the hydroamination of alkynes compared to the monocarboranyl phosphine analogs., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Pd II -catalyzed C(sp 3 )-H activation of free carboxylic acids represents a significant advance from conventional cyclopalladation initiated reactions. However, developing a modular synthetic platform for diverse quaternary and tertiary carbon centers based on this reactivity, two challenges remain to be addressed: mono-selectivity in each consecutive C-H functionalization step; compatibility with heteroatoms. While the exclusive mono-selectivity was achieved by β-lactonization/nucleophilic attack, the latter limitation remains to be overcome. Herein, we report the Pd II -catalyzed β- and γ-C(sp 3 )-H heteroarylation of free carboxylic acids using pyridine-pyridone ligands capable of overcoming these limitations. A sequence of three consecutive C(sp 3 )-H activation reactions of pivalic acid provides an unique platform for constructing diverse quaternary carbon centers containing heteroaryls which could serve as an enabling tool for escaping the flat land in medicinal chemistry., (© 2022 Wiley-VCH GmbH.)

A flurry of recent research has centered on harnessing the power of nickel catalysis in organic synthesis. These efforts have been bolstered by contemporaneous development of well-defined nickel (pre)catalysts with diverse structure and reactivity. In this report, we present ten different bench-stable, 18-electron, formally zero-valent nickel-olefin complexes that are competent pre-catalysts in various reactions. Our investigation includes preparations of novel, bench-stable Ni(COD)(L) complexes (COD=1,5-cyclooctadiene), in which L=quinone, cyclopentadienone, thiophene-S-oxide, and fulvene. Characterization by NMR, IR, single-crystal X-ray diffraction, cyclic voltammetry, thermogravimetric analysis, and natural bond orbital analysis sheds light on the structure, bonding, and properties of these complexes. Applications in an assortment of nickel-catalyzed reactions underscore the complementary nature of the different pre-catalysts within this toolkit., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

A one-dimensional (1D) halogen-bridged dinuclear-metal complex (MMX-chain) exhibits various electronic states based on a mixed-valence metal-dimer system. This report deals with the synthesis and physical properties of a new MMX-chain with a bulky pendant ligand, Pt 2 (mcc-HexCS 2 ) 4 I (mcc-HexCS 2 =trans-4-(methoxycarbonyl)cyclohexanedithiocarboxylate). The steric hindrance caused by the bulky substituent induces a strain in its 1D chain, achieving at ambient condition the first pure alternate charge-polarization (ACP) state (-Pt 2+ -Pt 3+ -I - -Pt 3+ -Pt 2+ -I - -), a kind of spin-Peierls state, as confirmed by X-ray diffraction and its conducting and magnetic properties. The strain effect is also manifested as a very large linear thermal expansion along the chain direction, which is quite different from conventional MMX-chains without a bulky ligand. The design of low-dimensional materials with ligand variations is expected to lead to the emergence of new electron-lattice coupled electronic states., (© 2022 Wiley-VCH GmbH.)

Perfluororhodacyclopentane supported by PBP pincer ligand PBP-Rh III (CF 2 ) 4 (2) was prepared from PBP-Rh I -PPh 3 (1) and tetrafluoroethylene (TFE). By scXRD analysis, it was revealed that the Rh-C F bond trans to the boryl ligand was largely elongated compared to the one in the apical position. Although M-C F bonds of perfluorometallacyclopentanes are known to be very stable, 2 shows high reactivity toward hydrogenolysis, iodinolysis and protonolysis, thanks to the strong trans-effect of the highly σ-donating boryl ligand. Analogous PCP pincer complex PCP-Rh III (CF 2 ) 4 (4) showed slower reaction rate both in oxidative cyclization with TFE and hydrogenolysis of Rh-C F bond. Catalytic production of 1,1,2,2,3,3,4,4-octafluorobutane from two TFE and hydrogen in one pot was achieved via repetitive oxidative cyclization of TFE and Rh followed by the hydrogenolysis of Rh-C F bonds. This report demonstrates the possible application of PBP-pincer skeleton to the preparation of fluorinated compounds from TFE., (© 2022 Wiley-VCH GmbH.)

Photoswitchable reagents can be powerful tools for high-precision biological control. TRPC5 is a Ca 2+ -permeable cation channel with distinct tissue-specific roles, from synaptic function to hormone regulation. Reagents giving spatiotemporally-resolved control over TRPC5 activity may be key to understanding and harnessing its biology. Here we develop the first photoswitchable TRPC5-modulator, BTDAzo, to address this goal. BTDAzo can photocontrol TRPC5 currents in cell culture, as well as controlling endogenous TRPC5-based neuronal Ca 2+ responses in mouse brain slices. BTDAzos are also the first reported azo-benzothiadiazines, an accessible and conveniently derivatised azoheteroarene with strong two-colour photoswitching. BTDAzo's ability to control TRPC5 across relevant channel biology settings makes it suitable for a range of dynamically reversible photoswitching studies in TRP channel biology, with the aim to decipher the various biological roles of this centrally important ion channel., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The development of C(sp 3 )-H functionalization reactions that use common protecting groups and practical oxidants remains a significant challenge. Herein we report a monoprotected aminoethyl thioether (MPAThio) ligand-enabled β-C(sp 3 )-H lactamization of tosyl-protected aliphatic amides using tert-butyl hydrogen peroxide (TBHP) as the sole oxidant. This protocol features exceedingly mild reaction conditions, reliable scalability, and the use of practical oxidants and protecting groups. Further derivatization of the β-lactam products enables the synthesis of a range of biologically important motifs including β-amino acids, γ-amino alcohols, and azetidines., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Aryl sulfones and aryl sulfonamides are of great importance in organic synthesis and medicinal chemistry. Although ortho-C-H functionalization of aryl sulfonyl compounds has been extensively explored, the functionalization of remote meta- and para-C-H bonds is very rare. Herein, we report a tunable meta- and para-selective C-H borylation of aryl sulfonyl compounds enabled by computationally designed ligands and iridium catalyst. This method is capable of accommodating a broad range of substrates under mild reaction conditions. Gram-scale preparation can be achieved with iridium catalyst loading as low as 0.1 mol%. As the introduced boronate group can be easily converted into many other groups, our method provides a general solution to installing functional groups at either meta- or para-position of aryl sulfones and aryl sulfonamides with good to excellent selectivity., (© 2022 Wiley-VCH GmbH.)

Ammonia oxidation catalyzed by molecular compounds is of current interest as a carbon-free source of dihydrogen. Activation of N-H bonds through coordination to transition metal centers is a key reaction in this process. We report the substantial activation of ammonia via reaction with low-valent molybdenum complexes of a diborate pentadentate ligand system. Spontaneous loss of dihydrogen from (B 2 Pz 4 Py)Mo II -NH 3 at room temperature to produce the dinuclear μ-nitrido compound (B 2 Pz 4 Py)Mo-N-Mo(B 2 Pz 4 Py) is observed due to substantial N-H bond weakening upon coordination to Mo. Mechanistic details are supported through the experimental observation/characterization of terminal amido, imido and nitrido complexes and density functional theory computations. The generally under-appreciated role of bridging nitrido intermediates is revealed and discussed, providing guidance for further catalyst development for this process., (© 2022 Wiley-VCH GmbH.)

Reversing the conventional site-selectivity of C-H activation processes provides new retrosynthetic disconnections to otherwise unreactive bonds. Here, we report a new catalytic system based on palladium/norbornene and an S,O-ligand for the meta-C-H arylation of aryl ethers that significantly outperforms previously reported systems. We demonstrate the unique ability of this system to employ alkoxyarene substrates bearing electron donating and withdrawing substituents. Additionally, ortho-substituted aryl ethers are well tolerated, overcoming the "ortho constraint", which is the necessity to have a meta-substituent on the alkoxyarene to achieve high reaction efficiency, by enlisting novel norbornene mediators. Remarkably, for the first time the monoarylation of alkoxyarenes is achieved efficiently enabling the subsequent introduction of a second, different aryl coupling partner to rapidly furnish unsymmetrical terphenyls. Further insight into the reaction mechanism was achieved by isolation and characterization of some Pd-complexes-before and after meta C-H activation-prior to evaluation of their respective catalytic activities., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The ubiquity of sulfur-containing molecules in biologically active natural products and pharmaceuticals has long attracted synthetic chemists to develop efficient strategies towards their synthesis. The strategy of direct α-C(sp 3 )-H modification of sulfides provides a streamlining access to complex sulfur-containing molecules. Herein, we report a photoinduced chemo-, site- and stereoselective α-C(sp 3 )-H functionalization of sulfides using isatins as the photoredox reagent and coupling partner catalyzed by a chiral gallium(III)-N,N'-dioxide complex. The reaction proceeds through a verified single-electron transfer (SET) mechanism with high efficiency, excellent functional group tolerance, as well as a broad substrate scope. Importantly, this cross-coupling protocol is highly selective for the direct late-stage functionalization of methionine-related peptides, regardless of the inherent structural similarity and complexity of diverse residues., (© 2022 Wiley-VCH GmbH.)

We report herein a facile and highly modular access to an intriguing class of free Au-substituted phosphines (AuPhos), namely (LAu) n PR 3-n (L=singlet carbene ligand; R=H, aryl, alkyl, silyl) (n=1-3). The Tolman electronic parameter (TEP) values coupled with theoretical investigations showcase that Au-substitution can boost the electron-releasing ability of AuPhos, thus leading to an electronically and sterically tunable, extremely electron-rich phosphorus center. The high basicity of AuPhos is attributed to the d-p lone pair π-repulsion arising from interaction between Au substituents and the lone pair at P. A series of multi-nuclear transition metal complexes (i.e. Rh, Ir, Pd, Au, W, Mn) ligated by AuPhos are readily prepared via a straightforward process. Preliminary catalytic results reveal the facilitation of Pd-catalyzed C-N coupling reactions and Ir-catalyzed decarbonylation reactions via AuPhos. This work provides insights for future development of electron-rich ligands., (© 2022 Wiley-VCH GmbH.)

New ligands for the iridium-catalyzed C(sp 3 )-H borylation of aliphatic compounds were established. In sharp contrast to 6-methyl-2,2'-bipyridine and 6-isobutyl-2,2'-bipyridine, 2,2'-bipyridine and 1,10-phenanthroline derivatives bearing a hydrosilylmethyl group (which would give a thermally stable NNSi pincer complex) served as suitable ligands for the reaction. Among them, a phenanthroline-based NNSi pincer ligand was shown to be an excellent ligand, and various aliphatic compounds were efficiently converted to the corresponding borylated products using the Ir/NNSi pincer catalyst system. The NNSi pincer ligand showed unique selectivity and enabled the iridium-catalyzed C(sp 3 )-H borylation using pinacolborane [H-B(pin)] instead of B 2 (pin) 2 . The formation of an iridium complex bearing a quinoline-based NNSi pincer ligand from [IrCl(cod)] 2 was observed, and the catalytic activity of the complex was demonstrated., (© 2022 Wiley-VCH GmbH.)

Enantioselective reactions that install functional groups at the positions of unactivated C-H bonds can be envisioned to produce intermediates for the synthesis of the active ingredients in pharmaceuticals and agrochemicals directly from simple feedstocks. Among these C-H bond functionalization reactions, those that form carbon-silicon (C-Si) and carbon-boron (C-B) bonds have been pursued because the products of these reactions can be converted to those containing a wide range of functional groups and because compounds containing silicon and boron possess unique properties that can be valuable for medicinal and materials chemistry. Although the silylation and borylation of C-H bonds have undergone extensive development during the past two decades, enantioselective versions of these reactions were not known until a few years ago. In this Minireview, we present the rapid development of enantioselective silylation and borylation of C-H bonds, with an emphasis on the design and development of the types of chiral ligands needed to achieve these reactions and an intention to inspire an expansion of these types of transformations., (© 2021 Wiley-VCH GmbH.)

A new cobalt catalyst is presented for the domino hydroformylation-reductive amination reaction of olefins. The optimal Co-tert-BuPy-Xantphos catalyst shows good to excellent linear-to-branched (n/iso) regioselectivity for the reactions of aliphatic alkenes with aromatic amines under mild conditions. This system is far more selective than traditional cobalt(I) catalysts and even better than most known rhodium catalysts., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The development of C(sp 3 )-H functionalizations of free carboxylic acids has provided a wide range of versatile C-C and C-Y (Y=heteroatom) bond-forming reactions. Additionally, C-H functionalizations have lent themselves to the one-step preparation of a number of valuable synthetic motifs that are often difficult to prepare through conventional methods. Herein, we report a β- or γ-C(sp 3 )-H carbonylation of free carboxylic acids using Mo(CO) 6 as a convenient solid CO source and enabled by a bidentate ligand, leading to convenient syntheses of cyclic anhydrides. Among these, the succinic anhydride products are versatile stepping stones for the mono-selective introduction of various functional groups at the β position of the parent acids by decarboxylative functionalizations, thus providing a divergent strategy to synthesize a myriad of carboxylic acids inaccessible by previous β-C-H activation reactions. The enantioselective carbonylation of free cyclopropanecarboxylic acids has also been achieved using a chiral bidentate thioether ligand., (© 2021 Wiley-VCH GmbH.)

In recent years, copper redox mediators have attracted growing interest in dye-sensitized solar cells (DSCs). However, experiments revealed that ubiquitously used Lewis-base additives in the electrolytes coordinate to the Cu II species, which restricts further enhancement of device performance and stability. We report the application of copper complexes endowed with diamine-tripyridine pentadentate ligands, [Cu(tpe)] 2+/+ (tpe=N-benzyl-N,N',N'-tris(pyridin-2-ylmethyl)ethylenediamine) and [Cu(tme)] 2+/+ (tme=N-benzyl-N,N',N'-tris(6-methylpyridin-2-ylmethyl)ethylenediamine), as redox mediators in DSCs. Experimental measurements demonstrate that the coordination environment of Cu(II) complexes with pentadentate ligands remains unchanged in the presence of TBP, which is in stark contrast to the state-of-the-art bipyridyl counterpart. DSCs based on [Cu(tme)] 2+/+ complexes exhibit an excellent long-term stability and maintain more than 90 % of the initial efficiency after 400 h under continuous illumination, which outperform the reference devices incorporating the bipyridyl counterpart (less than 80 %) under identical conditions., (© 2021 Wiley-VCH GmbH.)

An enantioselective sulfimidation of 3-thiosubstituted 2-quinolones and 2-pyridones was achieved with a stoichiometric nitrene source (PhI=NNs) and a silver-based catalyst system. Key to the success of the reaction is the use of a chiral phenanthroline ligand with a hydrogen bonding site. The enantioselectivity does not depend on the size of the two substituents at the sulfur atom but only on the binding properties of the heterocyclic lactams. A total of 21 chiral sulfimides were obtained in high yields (44-99 %) and with significant enantiomeric excess (70-99 % ee). The sulfimidation proceeds with high site-selectivity and can also be employed for the kinetic resolution of chiral sulfoxides. Mechanistic evidence suggests the intermediacy of a heteroleptic silver complex, in which the silver atom is bound to one molecule of the chiral ligand and one molecule of an achiral 1,10-phenanthroline. Support for the suggested reaction course was obtained by ESI mass spectrometry, DFT calculations, and a Hammett analysis., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The valence isoelectronic imido analog H 2 S(NtBu) 4 (1) of sulfuric acid H 2 SO 4 was synthesized, isolated, and characterized by NMR spectroscopy and high-resolution X-ray charge density analysis. The latter reveals strongly polarized S δ+ -N δ- bonds with virtually no double bond character. The easy-to-polarize S-N bonds are an advantageous and versatile feature of sulfur nitrogen ligands, which enables them to adapt to different electron requirements of various metal cations., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Boron reluctantly forms B=X (X=O, S, Se, Te) moieties, which has stimulated the quest for such species in the past few years. Based on the N,N'-chelating β-diketiminato ligand (HNacNac), a new amido imidazoline-2-imine ligand system (HAmIm) is presented, giving rise to the isolation of an exhaustive series of Lewis acid free, monomeric chalcogen B=X boranes with documented π-bond character between boron and the chalcogen. The chalcogenoboranes are isoelectronic and isolobal to the respective ketones. The chemical behavior of the oxoborane (B=O) strongly resembles the classical carbonyl reactivity in C=O bonds. The improved stability provided by HAmIm arises from the formation of more-stable five-membered boron chelates versus the six-membered NacNac analogues and from the imidazoline-2-imine moiety providing enhanced σ- and π-donation. The HAmIm ligand class may supersede the widely employed NacNac system in certain applications., (© 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The reactivity of Ni II and Pd II olefin polymerization catalysts can be enhanced by introduction of electron-withdrawing substituents on the supporting ligands rendering the metal centers more electrophilic. Reported here is a comparison of ethylene polymerization activity of a classical salicyliminato nickel catalyst substituted with the powerful electron-withdrawing 2,4,6-triphenylpyridinium (trippy) group to the -CF 3 analogue. The trippy substituent is substantially more electron-withdrawing (σ meta =0.63) than the trifluoromethyl group (σ meta =0.43) which results in a ca. 8-fold increase in catalytic turnover frequency. An additional advantage of trippy is the high steric bulk relative to the trifluoromethyl group. This feature results in a four-fold increase in polymer molecular weight owing to enhanced retardation of chain transfer. A significant increase in catalyst lifetime is observed as well., (© 2020 Wiley-VCH GmbH.)

The Ni-catalyzed N-arylation of β-fluoroalkylamines with broad scope is reported for the first time. Use of the air-stable pre-catalyst (PAd2-DalPhos)Ni(o-tol)Cl allows for reactions to be conducted at room temperature (25 °C, NaOtBu), or by use of a commercially available dual-base system (100 °C, DBU/NaOTf), to circumvent decomposition of the N-(β-fluoroalkyl)aniline product. The mild protocols disclosed herein feature broad (hetero)aryl (pseudo)halide scope (X=Cl, Br, I, and for the first time phenol-derived electrophiles), encompassing base-sensitive substrates and enantioretentive transformations, in a manner that is unmatched by any previously reported catalyst system., (© 2020 Wiley-VCH GmbH.)

Intramolecular 1,2-Dipp migration of seven mesoionic carbenes (iMIC Ar ) 2 a-g (iMIC Ar =ArC{N(Dipp)} 2 CHC; Ar=aryl; Dipp=2,6-iPr 2 C 6 H 3 ) under nickel catalysis to give 1,3-imidazoles (IMD Ar ) 3 a-g (IMD Ar =ArC{N(Dipp)CHC(Dipp)N}) has been reported. The formation of 3 indicates the cleavage of an N-C Dipp bond and the subsequent formation of a C-C Dipp bond in 2, which is unprecedented in NHC chemistry. The use of 3 in accessing super-iMICs (5) (S-iMIC=ArC{N(Dipp)N(Me)C(Dipp)}C) has been shown with selenium (6), gold (7), and palladium (8) compounds. The quantification of the stereoelectronic properties reveals the superior σ-donor strength of 5 compared to that of classical NHCs. Remarkably, the percentage buried volume of 5 (%V bur =45) is the largest known amongst thus far reported iMICs. Catalytic studies show a remarkable activity of 5, which is consistent with their auspicious stereoelectronic features., (© 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Regioselective transformation is among the long-standing challenges in organic synthesis. In this communication, a copper-catalyzed selectivity controlled regiodivergent borocarbonylation of imines with alkyl iodides has been developed. Various α-amino ketones and α-boryl amides were produced in moderate to good yields from the same substrates. The choice of the ligand is key for the regioselectivity control: α-amino ketones were produced selectively in good yields with (p-CF 3 C 6 H 4 ) 3 P as the ligand, whereas the corresponding α-boryl amides were obtained with high regioselectivities when using Me IMes as the ligand., (© 2020 Wiley-VCH GmbH.)

The synthesis of unprecedented BINOL-derived cationic phosphonites is described. Through the use of these phosphanes as ancillary ligands in Au I catalysis, a highly regio- and enantioselective assembly of appropriately designed alkynes into 1-(aryl)benzo[5]carbohelicenes is achieved. The modular synthesis of these ligands and the enhanced reactivity that they impart to Au I -centers after coordination have been found to be the key features that allow an optimization of the reaction conditions until the desired benzo[5]helicenes are obtained with high yield and enantioselectivity., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

This study describes the first palladium-catalyzed, site-selective α- and γ-arylation of α,β-unsaturated ketones with (hetero)aryl halides. A wide range of hetero(aryl)halides coupled with α,β-unsaturated ketones, and transformation into the arylated products proceeded with excellent to good yields. The site selectivity of the reaction is switchable by simply changing the phosphine ligand to access either α-arylated or γ-arylated products in good to excellent yields by using a low catalyst loading, and the method demonstrates good functional-group compatibility., (© 2020 Wiley-VCH GmbH.)

The first example of highly enantioselective fluoroarylation of gem-difluoroalkenes with aryl halides is presented by using a new chiral sulfinamide phosphine (Sadphos) type ligand TY-Phos. N-Me-TY-Phos can be easily synthesized on a gram scale from readily available starting materials in three steps. Salient features of this work including readily available starting materials, good yields, high enantioselectivities as well as broad substrate scope make this approach very practical and attractive. Notably, the asymmetric synthesis of an analogue of a biologically active molecule is also reported., (© 2020 Wiley-VCH GmbH.)

Iron(IV)-oxo intermediates in nature contain two unpaired electrons in the Fe-O antibonding orbitals, which are thought to contribute to their high reactivity. To challenge this hypothesis, we designed and synthesized closed-shell singlet iron(IV) oxo complex [(quinisox)Fe(O)] + (1 + ; quinisox-H=(N-(2-(2-isoxazoline-3-yl)phenyl)quinoline-8-carboxamide). We identified the quinisox ligand by DFT computational screening out of over 450 candidates. After the ligand synthesis, we detected 1 + in the gas phase and confirmed its spin state by visible and infrared photodissociation spectroscopy (IRPD). The Fe-O stretching frequency in 1 + is 960.5 cm -1 , consistent with an Fe-O triple bond, which was also confirmed by multireference calculations. The unprecedented bond strength is accompanied by high gas-phase reactivity of 1 + in oxygen atom transfer (OAT) and in proton-coupled electron transfer reactions. This challenges the current view of the spin-state driven reactivity of the Fe-O complexes., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

A series of structurally differentiated α-cationic phospholes containing cyclopropenium, imidazolium, and iminium substituents has been synthesized by reaction of chlorophosphole 1 with the corresponding stable carbenes. Evaluation of the donor properties of these compounds reveals that their strong π-acceptor character is heavily influenced by the nature of the cationic group. The coordination chemistry of these newly prepared ligands towards Au I centers is also described and their unique electronic properties exploited in catalysis. Interestingly, α-cationic phosphole containing catalysts were not only able to accelerate model cycloisomerization reactions, but also to efficiently discriminate between concurrent reaction pathways, avoiding the formation of undesired product mixtures., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

A new class of chiral cyclopentadienyl rhodium(I) complexes (CpRh I ) bearing C 2 -symmetric chiral bridged-ring-fused Cp ligands was prepared. The complexes were successfully applied to the asymmetric C-H activation reaction of N-methoxybenzamides with quinones, affording a series of chiral hydrophenanthridinones in up to 82 % yield with up to 99 % ee. Interestingly, structure analysis reveals that the side wall of the optimal chiral CpRh I catalyst is vertically more extended, horizontally less extended, and closer to the metal center in comparison with the classic binaphthyl and spirobiindanyl CpRh I complexes, and may thus account for its superior catalytic performance., (© 2020 Wiley-VCH GmbH.)

Triarylsilanolates are privileged ancillary ligands for molybdenum alkylidyne catalysts for alkyne metathesis but lead to disappointing results and poor stability in the tungsten series. 1 H, 183 W heteronuclear multiple bond correlation spectroscopy, exploiting a favorable 5 J-coupling between the 183 W center and the peripheral protons on the alkylidyne cap, revealed that these ligands upregulate the Lewis acidity to an extent that the tungstenacyclobutadiene formed in the initial [2+2] cycloaddition step is over-stabilized and the catalytic turnover brought to a halt. Guided by the 183 W NMR shifts as a proxy for the Lewis acidity of the central atom and by an accompanying chemical shift tensor analysis of the alkylidyne unit, the ligand design was revisited and a more strongly π-donating all-alkoxide ligand prepared. The new expanded chelate complex has a tempered Lewis acidity and outperforms the classical Schrock catalyst, carrying monodentate tert-butoxy ligands, in terms of rate and functional-group compatibility., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

The combination of more than one bioactive moiety in a multitargeted anticancer agent may result in synergistic activity of its components. Using this concept, bioorganometallic compounds were designed to feature a metal center, a 2-pyridinecarbothioamide (PCA), and a hydroxamic acid, which is found in the anticancer drug vorinostat (SAHA). The organometallics showed inhibitory activity in the nanomolar range against histone deacetylases (HDACs) as the key target for SAHA. In particular, the Rh complex was a potent inhibitor of HDAC6 over HDAC1 and HDAC8. Whereas this complex was highly cytotoxic in human cancer cells, it showed low toxicity in hemolysis studies and zebrafish, demonstrating the role of the metal center. For this complex a slightly reduced expression of vascular endothelial growth factor receptor 2 (VEGFR2) was established, which was upregulated by SAHA. This finding indicates that the new organometallics display different modes of action than their bioactive components., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

To explore the structure-function relationships of cobalt complexes in the catalytic hydrogen evolution reaction (HER), we studied the substitution of a tertiary amine with a softer pyridine group and the inclusion of a conjugated bpy unit in a Co complex with a new pentadentate ligand, 6-[6-(1,1-di-pyridin-2-yl-ethyl)-pyridin-2-ylmethyl]-[2,2']bipyridinyl (Py3Me-Bpy). These modifications resulted in significantly improved stability and activity in both electro- and photocatalytic HER in neutral water. [Co(Py3Me-Bpy)(OH 2 )](PF 6 ) 2 catalyzes the electrolytic HER at -1.3 V (vs. SHE) for 20 hours with a turnover number (TON) of 266 300, and photolytic HER for two days with a TON of 15 000 in pH 7 aqueous solutions. The softer ligand scaffold possibly provides increased stability towards the intermediate Co I species. DFT calculations demonstrate that HER occurs through a general electron transfer/proton transfer/electron transfer/proton transfer pathway, with H 2 released from the protonation of Co II -H species., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)