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The development of palladium‐catalyzed fluorination with biaryl monophosphine ligands has faced two important problems that limit its application for bromoarenes: the formation of regioisomers and insufficient catalysis for heteroaryl substrates as bromothiophene derivatives. Overcoming these problems requires more ligand design. In this work, reliable theoretical calculations were used to elucidate important ligand features necessary for achieving more rate acceleration and selectivity. These features include increasing the ligand‐substrate repulsion and creating a negative charge in the space around the fluoride ion bonded to the palladium. The investigated L5 ligand presents these features, and the calculations predict that this ligand completely suppresses the regioisomer formation in the difficult case of 4‐bromoanisole. In addition, the free energy barriers are decreased by 2–3 kcal mol−1 in comparison with the catalysis involving the AlPhos ligand. Thus, the present study points out a direction for new developments in palladium‐catalyzed fluorination. [ABSTRACT FROM AUTHOR]

Knölker complexes have been recently used to perform the catalytic C1‐oxidation of unprotected sugars into sugar lactones. This oxidation method remained limited by the stability of the catalyst with the polyhydroxylated substrates. Our objective is now to overcome these limitations and extend this method to more challenging substrates such as disaccharides. We proposed in this paper two original designs of Knölker‐type complexes conceived to promote secondary H‐bond interactions with the OH groups of the substrates to stabilise the system and favour the transformation. In total, 8 novel pre‐catalysts were synthesised, fully characterised and applied in the anomeric oxidation of several sugar derivatives. Two of these new complexes proved to be more efficient than the Knölker complex for the oxidation of disaccharides. Moreover, a preliminary DFT study revealed the presence of H‐bonds interactions between the substrate and the oxygen atom on the ligand arm of the best complexes suggesting a beneficial role of this heteroatom on the catalytic efficiency. [ABSTRACT FROM AUTHOR]

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−CH2Ar 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 %Vbur geometries ranging from 37.3 % to 52.7 %, with the latter representing the largest %Vbur 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 AuI complexes show superior catalytic performance in the hydroamination of alkynes compared to the monocarboranyl phosphine analogs. [ABSTRACT FROM AUTHOR]

Catalytic conversion of CO2 and hydrogen to methanol was achieved in a self‐separating multiphasic system comprising the tailor‐made complex [Ru(CO)ClH(MACHO‐C12)] (MACHO‐C12=bis{2‐[bis(4‐dodecylphenyl)phosphino]ethyl}amine) in n‐decane as the catalyst phase. Effective catalyst recycling was demonstrated for the carbonate and the amine‐assisted pathway from CO2 to methanol. The polar products MeOH or MeOH/H2O generated from the catalytic reactions spontaneously formed a separate phase, allowing product isolation and catalyst separation without the need for any additional solvent. In the amine‐assisted hydrogenation of CO2, the catalyst phase was recycled over ten subsequent runs, reaching a total turnover number to MeOH of 19200 with an average selectivity of 96 %. [ABSTRACT FROM AUTHOR]

In this study, dinuclear cobalt complexes (1 and 2) featuring bis(benzimidazole)pyrazolide‐type ligands (H2L and Me2L) were prepared and evaluated as molecular electrocatalysts for water oxidation. Notably, 1 bearing a non‐innocent ligand (H2L) displayed faster catalytic turnover than 2 under alkaline conditions, and the base dependence of water oxidation and kinetic isotope effect analysis indicated that the reaction mediated by 1 proceeded by a different mechanism relative to 2. Spectroelectrochemical, cold‐spray ionization mass spectrometric and computational studies found that double deprotonation of 1 under alkaline conditions cathodically shifted the catalysis‐initiating potential and further altered the turnover‐limiting step from nucleophilic water attack on (H2L)CoIII2(superoxo) to deprotonation of (L)CoIII2(OH)2. The rate–overpotential analysis and catalytic Tafel plots showed that 1 exhibited a significantly higher rate than previously reported Ru‐based dinuclear electrocatalysts at similar overpotentials. These observations suggest that using non‐innocent ligands is a valuable strategy for designing effective metal‐based molecular water oxidation catalysts. [ABSTRACT FROM AUTHOR]

The present review describes the homogenous catalytic methodologies for the synthesis of 2,2'‐bipyridines involving C−C bond formation from C−H bond. There are three main approaches to build well‐decorated 2,2'‐bipyridines from C−H bond cleavage: i) the formation of C2−C2′ bond by the dimerization of (activated) pyridines, ii) the C−H bond heteroarylation of activated pyridine, or iii) the late‐stage functionalization of (activated) 2,2'‐bipyridines including photoredox processes. Besides the scope and limitation of each methodologies, the relevant mechanisms of reaction are also discussed. [ABSTRACT FROM AUTHOR]

Novel seven‐membered cyclic imine‐based 1,3‐P,N ligands were obtained by capturing a Beckmann nitrilium ion intermediate generated in situ from cyclohexanone with benzotriazole, and then displacing it by a secondary phosphane under triflic acid promotion. These "cycloiminophosphanes" possess flexible non‐isomerizable tetrahydroazepine rings with a high basicity; this sets them apart from previously reported iminophophanes. The donor strength of the ligands was investigated by using their P‐κ1‐ and P,N‐κ2‐tungsten(0) carbonyl complexes, by determining the IR frequency of the trans‐CO ligands. Complexes with [RhCp*Cl2]2 demonstrated the hemilability of the ligands, giving a dynamic equilibrium of κ1 and κ2 species; treatment with AgOTf gives full conversion to the κ2 complex. The potential for catalysis was shown in the RuII‐catalyzed, solvent‐free hydration of benzonitrile and the RuII‐ and IrI‐catalyzed transfer hydrogenation of cyclohexanone in isopropanol. Finally, to enable access to asymmetric catalysts, chiral cycloiminophosphanes were prepared from l‐menthone, as well as their P,N‐κ2‐RhIII and a P‐κ1‐RuII complexes. [ABSTRACT FROM AUTHOR]

We describe a bundle for UCSF ChimeraX called SEQCROW that provides advanced structure editing capabilities and quantum chemistry utilities designed for complex organic and organometallic compounds. SEQCROW includes graphical presets and bond editing tools that facilitate the generation of publication‐quality molecular structure figures while also allowing users to build molecular structures quickly and efficiently by mapping new ligands onto existing organometallic complexes as well as adding rings and substituents. Other capabilities include the ability to visualize vibrational modes and simulated IR spectra, to compute and visualize molecular descriptors including percent buried volume, ligand cone angles, and Sterimol parameters, to process thermochemical corrections from quantum mechanical computations, to generate input files for ORCA, Psi4, and Gaussian, and to run and manage computational jobs. [ABSTRACT FROM AUTHOR]

Herein the synthesis of a new ethynyl ferrocenyl amidinate ligand [Fc−C≡C‐{C(Ndipp)2H}] (Fc=ferrocenyl; dipp=diisopropylphenyl) and the subsequent formation of the corresponding samarium amido complex [Sm{Fc−C≡C‐[C(Ndipp)2]}2{N(SiMe3)2}] is reported. [Fc−C≡C‐{C(Ndipp)2H}] and [Sm{Fc−C≡C‐[C(Ndipp)2]}2{N(SiMe3)2}] were fully characterized including the study of the complex' redox properties by cyclovoltammetry. Furthermore, we investigated the catalytic properties of the samarium complex in the intramolecular hydroamination reaction and intermolecular dehydrocoupling of pinacol borane with various amines. [ABSTRACT FROM AUTHOR]

Asymmetric gold catalysis has been rapidly developed in the past ten years. Breakthroughs have been made by rational design and meticulous selection of chiral ligands. This review summarizes newly developed gold‐catalyzed enantioselective organic transformations and recent progress in ligand design (since 2016), organized according to different types of chiral ligands, including bisphosphine ligands, monophosphine ligands, phosphite‐derived ligands, and N‐heterocyclic carbene ligands for asymmetric gold(I) catalysis as well as heterocyclic carbene ligands and oxazoline ligands for asymmetric gold(III) catalysis. [ABSTRACT FROM AUTHOR]

The reactivity of NiII and PdII 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 ‐CF3 analogue. The trippy substituent is substantially more electron‐withdrawing (σmeta=0.63) than the trifluoromethyl group (σmeta=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. [ABSTRACT FROM AUTHOR]

Transition metal‐catalyzed reactions in aqueous media are experiencing a constant increase in interest. In homogenous catalysis the use of water as a solvent offers advantages in cost, safety, the possibility of two‐phase catalysis and simplified separation strategies. In the life sciences, transition metal catalysis in aqueous systems enables the ligation or modification of biopolymers in buffer systems or even in their cellular environment. In biocatalysis, aqueous systems allow the simultaneous use of enzymes and transition metal catalysts in cascade reactions. The use of water‐soluble phosphine ligands still represents the most reliable and popular strategy for transferring metal catalysts into the aqueous phase. This review summarizes the recent advancements in this field since 2009 and describes current synthetic strategies for the preparation of hydrophilic phosphines and phosphites. In addition, recent applications of transition metal catalysis in aqueous solvents using these hydrophilic ligands are presented. [ABSTRACT FROM AUTHOR]

The pincer platform provides increased stability and often a rigid coordination mode in transition metal complexes that allows for the incorporation of reactive functional groups in the coordination sphere of a metal. Classical coordination patterns in pincer‐type complexes were established over the past decades, involving a preferred set of binding sites. In the current review, we discuss pincer‐type ligands with remarkable bonding situations and reactivity patterns, which are beyond the privileged ligand systems frequently used in homogeneous catalysis and bond activation reactions. This includes ligands with ligating atoms based on metalloid elements, π‐systems as well as different kinds of metallo‐ligands. We categorize the discussed pincer‐type ligands herein according to the covalent bond classification and distinguish between metallo‐ligands and ligands, which are based on nonmetal and metalloid elements. [ABSTRACT FROM AUTHOR]

In various nickel(II) salicylaldiminato ethylene polymerization catalysts, which are a versatile mechanistic probe for substituent effects, longer perfluoroalkyl groups exert a strong effect on catalytic activities and polymer microstructures compared to the trifluoromethyl group. This effect is accounted for by a reduced electron density on the active sites, and is also supported by electrochemical studies. Thus, β‐hydride elimination, the key step of chain transfer and branching pathways, is disfavored while chain‐growth rates are enhanced. This enhancement occurs to an extent that enables living polymerizations in aqueous systems to afford ultra‐high‐molecular‐weight polyethylene for various chelating salicylaldimine motifs. These findings are mechanistically instructive as well as practically useful for illustrating the potential of perfluoroalkyl groups in catalyst design. [ABSTRACT FROM AUTHOR]

The formal insertion of alkenes into aromatic chloro‐ and bromoalkynes takes place under cationic gold catalysis. This haloalkynylation reaction can be performed with cyclic, gem‐disubstituted and monosubstituted alkenes, using BINAP, triazolo[4,3‐b]isoquinolin‐3‐ylidene ligands or SPhos, respectively. The products were isolated in moderate to excellent yields and with complete diastereo‐ and regioselectivity; the halogen atom bonding the more substituted carbon of the alkene. Preliminary experiments showed that the enantioselective haloalkynylation of cyclopentene can be performed with (S)‐BINAP to afford the insertion products with moderate to good enantioselectivities. [ABSTRACT FROM AUTHOR]

The PNNP ligand (R,R)‐{PPh2(2‐C6H4)CH=N(pyrrolidine‐NBn)‐}22 was prepared by condensation between 2‐diphenylphosphino benzaldehyde and the pyrrolidine‐substituted diamine 1. Reduction with NaBH4 in MeOH afforded (R,R)‐{PPh2(2‐C6H4)CH–NH(pyrrolidine‐NBn)‐}23. The corresponding iron(II) complexes [FeCl2(2)] (4), [Fe(CH3CN)2(2)](BF4)2 (5) and [Fe(CH3CN)2(2)](PF6)2 (6) were synthesized and fully characterized by NMR, ESI‐HRMS, and EA. DFT calculations for complexes [FeCl2(2)] (4) and [Fe(CH3CN)2(2)](BF4)2 (5) were carried out in order to investigate the stability of related structures. The PNNP ligands 2 and 3 in combination with Fe3(CO)12 as iron source were tested as catalysts in the asymmetric transfer hydrogenation of a variety of ketones with conversions higher than 95 % and enantioselectivities up to 97 %. [ABSTRACT FROM AUTHOR]

In the palladium‐catalysed methoxycarbonylation of technical propyne, the presence of propadiene poisons the hemilabile Pd(P,N) catalyst. According to density functional theory calculations (B3PW91‐D3/PCM level), a highly stable π‐allyl intermediate is the reason for this catalyst poisoning. Predicted regioselectivities suggest that at least 11 % of propadiene should yield this allyl intermediate, in which the reaction gets stalled under the turnover conditions due to an insurmountable methanolysis barrier of 25.8 kcal mol−1. The results obtained for different ligands and substrates are consistent with the available experimental data. A new ligand, (6‐Cl‐3‐Me‐Py)PPh2, is proposed, which is predicted to efficiently control the branched/linear selectivity, avoiding rapid poisoning (with only 0.2 % of propadiene being trapped as the Pd allyl complex), and to tremendously increase the catalytic activity by decreasing the overall barrier to 9.1 kcal mol−1. [ABSTRACT FROM AUTHOR]

• Water-soluble phosphine ligands find application in two-phase catalysis and facilitate combination of chemo- and biocatalysis, as both reaction types occur in the same aqueous reaction medium. • A directed metalation strategy allows the synthesis of water-soluble dppf ligands with hydrophilic sulfonate groups attached to the ferrocene core. • The introduction of hydrophilic sulfonate resp. ammonium entities at the phenyl groups of dppf gives water-soluble dppf variants with even higher solubility in water. • The identity and electronic properties of these ligands could be characterized via X-ray structure analysis and 31P-NMR spectroscopy. • These ligands enable the Pd-catalyzed Tsuji-Trost allylation of aromatic and aliphatic amines in pure (!) water as solvent, delivering pharmaceutically relevant target molecules in an environmentally benign process. Hydrophilic phosphine ligands have proven indispensable for the translation of metal-catalyzed reactions into aqueous solvent systems and thus for the implementation of safe as well as sustainable chemical processes. Despite numerous reports on water-soluble variants of several renowned ligands, the dppf ligand family has been neglected thus far. Herein, we disclose synthetic strategies towards the first hydrophilic dppf derivatives overcoming issues typically encountered due to their intrinsic oxidizability. Core-sulfonated dppf ligands (meso ‑2,2′- or 2,5-disubstituted) were prepared by a directed metalation strategy starting from diisopropyl ferrocene-1,1′-disulfonate. Alternatively, hydrophilic sulfonate or ammonium groups were introduced at the phenyl substituents of dppf. The novel ligands were spectroscopically characterized and showed their catalytic potential in the Pd-catalyzed Tsuji-Trost allylation of amines in water furnishing pharmaceutically relevant N -allylated products (e.g., naftifine, cinnarizine) through a scalable, safe and environmentally benign process. [Display omitted] [ABSTRACT FROM AUTHOR]

Three triazolylmethylpyridine ligands are synthesized using the copper‐catalyzed azide‐alkyne cycloaddition (CuAAC). The corresponding copper(I) complexes are investigated as catalysts for the oxygenation of several monophenols, in analogy to the enzyme tyrosinase. Importantly, they show a higher catalytic activity than previously investigated systems. This is ascribed to the lower charge donation of the electron‐poor triazole heterocycle, supporting the hydroxylation of phenolic substrates by an electrophilic substitution mechanism. Click. Coordinate. Catalyze. Bidentate ligands with triazole groups are readily synthesized via a copper catalyzed azide‐alkyne cycloaddition. Their copper complexes turn out to be highly active catalysts for the oxygenation of various monophenols, in analogy to the enzyme tyrosinase. [ABSTRACT FROM AUTHOR]

Abstract: In view of literature reports, benzo[h]quinoline and its substituted analogues, due to their structural similarity to 2‐phenylpyridine derivatives, appear to be very promising C,N‐cyclometalating ligands for iridium‐based Phosphorescent Organic Light Emitting Diode technology. 5‐bromo‐benzo[h]quinoline aroused our particular interest as a convenient precursor for further transformations, and was successfully functionalized in the course of transition metal‐promoted exclusive C−C, C−O and C−N bond formation, yielding a series of 5‐substituted benzo[h]quinoline derivatives with unique structures and properties. Some of the synthesized compounds seemed to be appropriate starting materials for subsequent transformations, and enabled the preparation of new benzo[h]quinoline‐based materials, for instance those with fluorine or silsesquioxane groups, which have not been synthesized by the conventional Scraup protocol. In selected transformations, the assistance of microwave irradiation as a non‐conventional energy carrier significantly improved efficiency, leading to the formation of desired products with yields of up to 99%. [ABSTRACT FROM AUTHOR]

Abstract: That of carbones is a new family member in the class of low‐valent carbon compounds. Unlike its cousin, the conventional carbene, the carbone possesses two free electron lone pairs. In combination with their unique allene‐type structure, they possess stronger σ‐donating ability than conventional carbenes such as NHCs or CAACs. Because of this property, they have a huge potential to become a new class of ligands in organometallic chemistry and catalysis. Although carbodiphosphoranes (CDP) were initially discovered in 1961, nearly 50 years were needed to attract the attention of the chemical community with the synthesis of the carbodicarbene (CDC). This Concept paper summarizes developments over the last 10 years and future outlooks for this new class of σ‐donors, particularly carbodicarbenes. [ABSTRACT FROM AUTHOR]

The first transition metal catalyzed hydrophosphination of isocyanates is presented. The use of low-coordinate iron(II) precatalysts leads to an unprecedented catalytic double insertion of isocyanates into the P−H bond of diphenylphosphine to yield phosphinodicarboxamides [Ph2PC(=O)N(R)C(=O)N(H)R], a new family of derivatized organophosphorus compounds. This remarkable result can be attributed to the low-coordinate nature of the iron(II) centers whose inherent electron deficiency enables a Lewis-acid mechanism in which a combination of the steric pocket of the metal center and substrate size determines the reaction products and regioselectivity. [ABSTRACT FROM AUTHOR]

Keywords: Carboranes; Homogeneous Catalysis; Ligand Design; Phosphines; Strong Donors; Transition Metal Complexes EN Carboranes Homogeneous Catalysis Ligand Design Phosphines Strong Donors Transition Metal Complexes 1 1 1 03/23/23 20230327 NES 230327 B Carboranes b . Frontispiece: On the Edge of the Known: Extremely Electron-Rich (Di)Carboranyl Phosphines Carboranes, Homogeneous Catalysis, Ligand Design, Phosphines, Strong Donors, Transition Metal Complexes. [Extracted from the article]

For the first time, structurally defined manganese pincer complexes catalyze the dehydrogenation of aqueous methanol to hydrogen and carbon dioxide, which is a transformation of interest with regard to the implementation of a hydrogen and methanol economy. Excellent long-term stability was demonstrated for the Mn-PNP iPr catalyst, as a turnover of more than 20 000 was reached. In addition to methanol, other important hydrogen carriers were also successfully dehydrogenated. [ABSTRACT FROM AUTHOR]

A straightforward route for the preparation of a set of bis(cyclopropenium)-substituted phosphines is reported. Due to their dicationic nature, these ligands depict an excellent π-acceptor character. The effect of the ligand substituent pattern on the catalytic activity of the metal complexes thereof derived is also studied. Whereas sterically demanding biaryl groups directly attached to the phosphorus atom seem to facilitate elementary steps such as the product release from the catalyst, long chain dialkylamino groups on the cyclopropenium units maximize the catalysts solubility and, thus, allow the use of typical apolar solvents such as toluene. Importantly, all new ligands prepared can be easily handled in air. Finally, the impact of the newly prepared dicationic phosphines in hydroarylation reactions is demonstrated. In particular, their use in the synthesis of several naphtho[1,2- b]furanes and naturally occurring naphthalene derivatives such as Calanquinone C is reported. [ABSTRACT FROM AUTHOR]

The synthesis and structure of the first 1,2-bis(NHSi)-substituted ortho-carborane [(LSi:)C]2B10H10 (termed SiCCSi) is reported (NHSi= N-heterocyclic silylene; L=PhC(NtBu)2). Its suitability to serve as a reliable bis(silylene) chelating ligand for transition metals is demonstrated by the formation of [SiCCSi]NiBr2 and [SiCCSi]Ni(CO)2 complexes. The CO stretching vibration modes of the latter indicate that the SiII atoms in the SiCCSi ligand are even stronger σ donors than the PIII atoms in phosphines and CII atoms in N-heterocyclic carbene (NHC) ligands. Moreover, the strong donor character of the [SiCCSi] ligand enables [SiCCSi]NiBr2 to act as an outstanding precatalyst (0.5 mol % loading) in the catalytic aminations of arenes, surpassing the activity of previously known molecular Ni-based precatalysts (1-10 mol %). [ABSTRACT FROM AUTHOR]

The utility of RockPhos, Ad-BippyPhos, JosiPhos (CyPF- tBu), and Mor-DalPhos in palladium-catalyzed C-O cross-coupling reactions involving aliphatic alcohols and (hetero)aryl halides under analogous conditions was examined, both at room temperature and at elevated temperature (90 °C). In general, the RockPhos-based catalyst system proved superior, especially at room temperature, but catalysts based on the other ligands examined also proved effective across a range of C-O cross-couplings, in some cases providing better catalytic performance than RockPhos. New reactivity was established in terms of the scope of room temperature reactions. Proof-of-principle examples of such cross-couplings involving aryl mesylates were also demonstrated. [ABSTRACT FROM AUTHOR]

PdII complexes with PPh( o-C6H4SMe)2 acting as a pincer ligand in an S, S′, P- or S, P-coordination mode have been synthesized. The complexes include [PdCl2{PPh( o-C6H4SMe)2}] ( 1), [Pd(Me)Cl{PPh( o-C6H4SMe)2}] ( 2), and [Pd(X){PPh( o-C6H4SMe)2}]A [A = CF3SO3, X = Cl ( 3); A = CF3SO3, Me ( 4); A = PF6, X = Me ( 5)]. Insertion of CO into the Pd-Me bond of these complexes leads to [Pd(COMe)Cl{PPh( o-C6H4SMe)2}] ( 6) and [Pd(COMe){PPh( o-C6H4SMe)2}]A [A = CF3SO3 ( 7); A = PF6 ( 8)]. Some of these complexes are good Mizoroki-Heck catalysts (for the reactions between iodobenzene and methyl acrylate or styrene). The most active catalyst was found to be [Pd(Me)Cl{PPh( o-C6H4SMe)2}] ( 2). This catalyst could be retained on a silica gel column, recovered, and reused several times without losing activity. [ABSTRACT FROM AUTHOR]

Chiral monodentate phosphines based on ortho-disubstituted ferrocene units have been prepared and used for the synthesis of gold(I) complexes. These complexes are highly active catalysts for the cycloisomerization of 3-hydroxy-1,5-enynes into bicyclo[3.1.0]hexanones. Their high catalytic activity is ascribed to their structural analogy to the biaryl-based Buchwald phosphines. This paper discloses the first enantioselective variant of these reactions based on gold catalysis ( ee's up to 80 %). [ABSTRACT FROM AUTHOR]

Ligand design for metal-ligand cooperative (MLC) catalysis is inherently more complex than that for traditional non-cooperative ligands. The basicity, sterics and structure of the acid/base group in MLC proton-transfer (PT) complexes, for instance, undoubtedly influence catalyst performance. Herein, we evaluate the highly tunable PR2NR′2 (1,5-R′-3,7-R-1,5-diaza-3,7-diphosphacyclooctane) ligand family for the first time in an organic transformation. With [Ru(Cp)(P tBu2NBn2)(MeCN)][PF6] as the catalyst, no turnover was observed in the anti-Markovnikov hydration of alkynes, a known PT MLC reaction. Treatment of the cooperative complex with phenylacetylene affords a vinylammonium product in which the pendant nitrogen atom of the P tBu2NBn2 ligand forms a Lewis acid-base adduct with the alpha-carbon atom of the vinylidene intermediate. Characterization by X-ray crystallography and NMR spectroscopy conclusively assign this structure in both the solid and the solution state. The adduct formation is irreversible, and the adduct is characterized as a catalyst deactivation product. [ABSTRACT FROM AUTHOR]

A domino aza-Cope/aza-Prins cascade enabled the synthesis of a new class of 4-hydroxypiperidine-appended mono, bis, tris, and tetrakis unimolecular compounds that served as efficient ligands to catalyze Suzuki-Miyaura cross-coupling reactions under aerobic conditions. Various biaryls, terphenyls, and heterocyclic biphenyls were obtained in good to excellent yields. The ligands were also capable of catalyzing the Heck-Mizoroki reaction. As an application, the Suzuki-Miyaura coupling reaction was used in the synthesis of incrustoporin, its analogs, and the drug molecule preclamol. [ABSTRACT FROM AUTHOR]

Biphenyl-based arsine ligands were prepared in two-step fashion by Pd-catalyzed arsination and microwave-assisted Suzuki--Miyaura coupling, providing sterically demanding arsine ligands in overall isolated yields up to 82% as air-stable solids. Short reaction times were achieved with the assistance of microwave irradiation in the direct and simple described protocol for the synthesis of biarylarsine ligands. The activities of the biphenyl arsine ligands were explored in Pd-catalyzed Heck coupling. As a general trend, the ligands with "blocked" ortho-positions on the non-arsine-containing ring of the biphenyl backbone performed more efficiently in the coupling reaction. This catalytic system allowed several interesting stilbenes to be obtained in very good yields. [ABSTRACT FROM AUTHOR]

Stable heteroleptic amido YbII and SmII complexes bearing aminoether-phenolate ligands and devoid of coordinated solvent have been structurally characterized. They afford highly active, chemoselective and, in the case of monoadditions, 100 % anti-Markovnikov regiospecific catalysts (down to 0.04 mol % loading) for the hydrophosphination of styrene with PhPH2 under mild conditions. [ABSTRACT FROM AUTHOR]

The synthesis of a light-responsive N-heterocyclic carbene copper(I) complex by introducing a nitrobenzospiropyran unit into the carbene ligand was developed. The solubility of this complex was controlled through reversible conversion between its netural and ionic states using ultraviolet light irradiation. Taking advantage of such a light-sensitive property facilitated its recovery and reuse in copper(I)-catalyzed homogeneous oxidation and "click" reactions. [ABSTRACT FROM AUTHOR]

A catalyst that couples a photoswitch to the biaryl backbone of a chiral bis(phosphine) ligand, thus allowing photochemical manipulation of ligand geometry without perturbing the electronic structure is reported. The changes in catalyst activity and selectivity upon switching can be attributed to intramolecular mechanical forces, thus laying the foundation for a new class of catalysts whose selectivity can be varied smoothly and in situ over a useful range by controlling molecular stress experienced by the catalyst during turnover. Forces on the order of 100 pN are generated, thus leading to measurable changes in the enantioselectivities of asymmetric Heck arylations and Trost allylic alkylations. The differential coupling between applied force and competing stereochemical pathways is quantified and found to be more efficient for the Heck arylations. [ABSTRACT FROM AUTHOR]

Reaction of the noninnocent iminophenol-iminopyridine hybrid ligand HLIPIP, where LIPIP denotes [2-(( E)-{( E)-2-[( E)-pyridin-2-ylmethyleneamino]benzylidene}amino)-4,6-di- tert-butylphenolate], with copper acetate afforded a copper complex, LAPIPCuII, in which one of the imine functional groups is oxidized to an amide during metal complexation. The new CuII complex is capable of catalyzing efficient aerobic alcohol oxidation under mild conditions. The crystal structure of LAPIPCuII exhibits a square-planar geometry with the CuII center coordinated by three nitrogen atoms and one oxygen atom. Electrochemical studies were conducted to evaluate the redox-active behavior of the complex, and the results showed a quasireversible reduction and a ligand-based oxidation process. The neutral species of LAPIPCuII is EPR active, which is consistent with a paramagnetic electronic ground state (d9, S = 1/2), whereas the one-electron oxidized complex was X-band EPR silent. One-electron chemical oxidation of LAPIPCuII gave a new species that can be attributed to a CuII-phenoxyl radical complex. Based on EPR measurements in conjunction with density functional theory calculations, [LAPIPCuII]+ is proposed to have a triplet electronic ground state, exhibiting a weak ferromagnetic interaction between the CuII center and the coordinated phenoxyl radical. [ABSTRACT FROM AUTHOR]

Since the first report in the early 1950s, 1,3-bis(2-pyridylimino)isoindolines (BPIs) have found widespread applications in organic, inorganic and materials chemistry. This microreview focuses on recent progress towards chiral BPI derivatives as ligands for enantioselective catalysis as well as developments in the use of BPI complexes in materials science, focusing on luminescent and birefringent materials. [ABSTRACT FROM AUTHOR]

A new family of cationic ligands, N-alkyl/aryl pyridiniophosphines, has been synthesized through a short, scalable, and highly modular route. Evaluation of their electronic properties evidenced weak σ-donor and quite strong π-acceptor character when used as ancillary ligands. These attributes confer a substantially enhanced π-acidity to the PtII and AuI complexes thereof derived and, as result, they depict an improved ability to activate alkynes towards nucleophilic attack. This superior performance has been demonstrated along several mechanistically diverse PtII- and AuI-catalyzed transformations. [ABSTRACT FROM AUTHOR]

Starting from tartaric acid derived chiral diols or dicarboxylic acid dichlorides with either a 2,2-dimethyl-1,3-dioxolane (Taddol) or a 2,3-dimethoxy-2,3-dimethyl-1,4-dioxane (Tatrol) core structure, and BH3-protected ortho-phosphanyl phenols, a set of fourteen new C2-symmetric diphosphine ligands was synthesized. In addition, three related ligands were obtained from ortho-diphenylphosphino-anilines. The fully characterized ligands were then tested in the Pd-catalyzed enantioselective O-allylation of 4-methoxyphenol using crotyl methyl carbonate as a reagent. In addition, a pseudo-intramolecular variant of the reaction, using crotyl 4-methoxyphenyl carbonate as a substrate, was studied. The so-called Trost ligand was used as a reference. Although the Trost ligand (3 mol-%) gave up to 84 % ee, one of the new ligands showed higher activity (50 % ee with 0.075 mol-%). [ABSTRACT FROM AUTHOR]

Abstract: Asymmetric hydrogenation of ketones (AHK) was revolutionized in 1987 and again in 1995 when Ru(CH3COO)2(binap)/HCl and RuCl2(binap)/diamine, respectively, were developed. Since then, the number of reports on Ru-catalyzed AHK has increased exponentially, and the utility of other precious metals (Os, Rh, Ir, and Pd) has also been shown. The utilization of inexpensive base metals (Fe, Co, Ni, and Cu) has been a recent trend. This digest summarizes the key advances in AHK in the past decade by categorizing the chiral ligands into six types: (i) diphosphines, (ii) diphosphines/diamines, (iii) tridentate or tetradentate phosphine amines, (iv) diamines, (v) tetradentate amines, and (vi) tetradentate thioether amines. [Copyright &y& Elsevier]

Computational studies, especially those that use density functional theory (DFT), have become pervasive in the characterization, mechanistic study, and optimization of homogeneous organometallic catalysts, and the 'rational' design of such catalysts seems within reach once more. But how advanced, user-friendly, and reliable are the computational tools that are currently available? Here we summarize the current state of the art for predictive computational organometallic chemistry in reference to the different stages of catalyst development by considering characterization, mechanistic studies, fine-tuning/optimization, and evaluation of novel designs. We also assess critically where the strengths and weaknesses of computational studies lie and hence map out the road ahead for the design and discovery of novel catalysts in silico and in combination with targeted experimental studies. [ABSTRACT FROM AUTHOR]

A rigid anilido bipyridyl ligand has been designed for use in an organoscandium-based carbon dioxide hydrosilation catalyst. Ligand attachment by alkane elimination results in metalation of an aryl CH bond in a 3,5-di- tert-butylphenyl group installed on the pyridyl unit, thus rendering the ligand tetradentate. Insertion of CO2 into the newly formed ScC bond leads to a κ1 carboxylate which, when treated with the borane B(C6F5)3, becomes hemilabile. In addition to activating the catalyst, the k1 carboxylate effectively sequesters free B(C6F5)3 and the ensemble is able to effectively hydrosilate CO2, in the presence of excess Et3SiH, almost exclusively to R3SiOCH2OSiR3. A maximum turnover number of about 3400 (conversion of silane) is observed. Mechanistic experiments suggest that the sequestration of free B(C6F5)3 by the hemilabile carboxylate contributes to the selectivity observed and prevents over reduction to methane. [ABSTRACT FROM AUTHOR]

A library of bis(phosphane) ligands based on the 2,8-substituted Tröger's base scaffold was synthesized through an efficient two-step protocol by starting from a commercially available aniline. The new ligands proved their efficiency in palladium-catalyzed Suzuki-Miyaura cross-coupling reactions and Buchwald-Hartwig aminations of aryl chlorides and bromides. [ABSTRACT FROM AUTHOR]