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A well-defined silica-supported tungsten oxo alkylidene is a highly active alkene metathesis catalyst
Grafting (ArO)2W(i=O)(i=CHtBu) (ArO = 2,6-mesitylphenoxide) on partially dehydroxylated silica forms mostly [(i - SiO)W(i=O)(i=CHtBu) (OAr)] along with minor amounts of [(i - SiO)W(i=O)(CH2tBu) (OAr)2] (20%), both fully ch
Conley, Matthew P.,Mougel, Victor,Peryshkov, Dmitry V.,Forrest, William P.,Gajan, David,Lesage, Anne,Emsley, Lyndon,Coperet, Christophe,Schrock, Richard R.
p. 19068 - 19070
(2013)
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Miyaura,N. et al.
p. 669 - 670
(1975)
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Benchmarked Intrinsic Olefin Metathesis Activity: Mo vs. W
Combining Surface Organometallic Chemistry with rigorous olefin purification protocol allows evaluating and comparing the intrinsic activities of Mo and W olefin metathesis catalysts towards different types of olefin substrates. While well-defined silica-supported Mo and W imido-alkylidenes show very similar activities in metathesis of internal olefins, Mo catalysts systematically outperform their W analogs in metathesis of terminal olefins, consistent with the formation of stable unsubstituted W metallacyclobutanes in the presence of ethylene. However, Mo catalysts are more prone to induce olefin isomerization, in particular when ethylene is present, probably because of their propensity to undergo more easily reduction processes.
Zhizhko, Pavel A.,Mougel, Victor,De Jesus Silva, Jordan,Copéret, Christophe
(2018)
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Bulky aryloxide ligand stabilizes a heterogeneous metathesis catalyst
The reaction of [W(=O)(=CHCMe2Ph)(dAdPO)2], containing bulky 2,6-diadamantyl aryloxide ligands, with partially dehydroxylated silica selectively yields a well-defined silica-supported alkylidene complex, [(≡SiO)W(=O)(= CHCMe2Ph)(dAdPO)]. This fully characterized material is a very active and stable alkene metathesis catalyst, thus allowing loadings as low as 50 ppm in the metathesis of internal alkenes. [(≡SiO)W(=O)(=CHCMe2Ph)(dAdPO)] also efficiently catalyzes the homocoupling of terminal alkenes, with turnover numbers exceeding 75 000 when ethylene is constantly removed to avoid the formation of the less reactive square-based pyramidal metallacycle resting state.
Conley, Matthew P.,Forrest, William P.,Mougel, Victor,Copret, Christophe,Schrock, Richard R.
p. 14221 - 14224
(2014)
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Quantitatively Analyzing Metathesis Catalyst Activity and Structural Features in Silica-Supported Tungsten Imido-Alkylidene Complexes
A broad series of fully characterized, well-defined silica-supported W metathesis catalysts with the general formula [(≡SiO)W(=NAr)(=CHCMe2R)(X)] (Ar = 2,6-iPr2C6H3 (AriPr), 2,6-Cl2C6H3 (ArCl), 2-CF3C6H4 (ArCF3), and C6F5 (ArF5); X = OC(CF3)3 (OtBuF9), OCMe(CF3)2 (OtBuF6), OtBu, OSi(OtBu)3, 2,5-dimethylpyrrolyl (Me2Pyr) and R = Me or Ph) was prepared by grafting bis-X substituted complexes [W(NAr)(=CHCMe2R)(X)2] on silica partially dehydroxylated at 700 C (SiO2-(700)), and their activity was evaluated with the goal to obtain detailed structure-activity relationships. Quantitative influence of the ligand set on the activity (turnover frequency, TOF) in self-metathesis of cis-4-nonene was investigated using multivariate linear regression analysis tools. The TOF of these catalysts (activity) can be well predicted from simple steric and electronic parameters of the parent protonated ligands; it is described by the mutual contribution of the NBO charge of the nitrogen or the IR intensity of the symmetric N-H stretch of the ArNH2, corresponding to the imido ligand, together with the Sterimol B5 and pKa of HX, representing the X ligand. This quantitative and predictive structure-activity relationship analysis of well-defined heterogeneous catalysts shows that high activity is associated with the combination of X and NAr ligands of opposite electronic character and paves the way toward rational development of metathesis catalysts.
Mougel, Victor,Santiago, Celine B.,Zhizhko, Pavel A.,Bess, Elizabeth N.,Varga, Jeno,Frater, Georg,Sigman, Matthew S.,Copéret, Christophe
p. 6699 - 6704
(2015)
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Synthesis of erythromycin derivatives via the olefin cross-metathesis reaction
Olefin cross metathesis (CM) was applied to the synthesis of 6-O-substituted erythromycin derivatives. The reactions were catalyzed by transition metal alkylidene complexes, particularly bis(tricyclohexylphosphine)benzylidine ruthenium (IV) dichloride (Grubbs' first-generation catalyst). This approach allowed for the elaboration of the 6-O-allyl group of highly functionalized macrolides at various stages of the synthetic sequence, affording 6-O-3-aryl-propenyl products with excellent E-selectivity. Little or no self-dimerization of the reacting components was found in the crude mixtures. Preliminary kinetic data accounts for the observed cross-selectivity based on substrate reactivity and steric factors.
Hsu, Margaret C.,Junia, Adam J.,Haight, Anthony R.,Zhang, Weijiang
p. 3907 - 3911
(2004)
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Metathesis of hex-1-ene in ionic liquids
The WCl6 + BMIMBF4 and NaReO4 + BMIMCl-AICl3 (BMIM is l-butyl-3-methylimidazolium) systems are effective catalysts for the metathesis of hex-1-ene to form oct-4-ene.
Vasnev, Alexander V.,Greish, Alexander A.,Kustov, Leonid M.
p. 59 - 61
(2004)
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Photochemistry of trivinylboranes: Preparation of anti-adducts of hydroboranes and alkynes
Trivinylboranes, which are conveniently prepared from the addition of diborane to acetylenes, are found to readily undergo photochemical Z/E isomerization. Since the chromaphore of the E-isomer is highly twisted by steric strain, photochemical conditions can completely convert the Z-isomer to the E-isomer. This high yield, two step process, provides an efficient procedure to bring about an anti-addition of hydroboranes to acetylenes.
Gano,Srebnik
p. 4889 - 4892
(1993)
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Increasing Olefin Metathesis Activity of Silica-Supported Molybdenum Imido Adamantylidene Complexes through E Ligand σ-Donation
Molybdenum imido adamantylidene complexes with different substituents on the imido ligand (dipp=2,6-diisopropylphenyl, ArF5=C6F5, and tBu) having distinct electron donating abilities were investigated for the metathesis of internal and terminal olefins, for both molecular and silica-supported species using standardized protocols. Here we show that surface immobilization of these compounds results in dramatically increased activity compared to their molecular counterparts. Additionally, we show that electron withdrawing imido groups increase the activity of the compound towards terminal olefins while they simultaneously decrease the ability to metathesize internal olefins. Furthermore, these systems also show high stability when used as initiators in olefin metathesis, although the species that display higher initial activity deactivate faster than those that show more a more moderate reaction rate at first. Our catalytic studies, augmented by DFT calculations, show that all investigated compounds have a remarkably small energy difference between the trigonal bipyramidal (TBP) and square planar (SP) configurations of the metallacyclobutane intermediates, which has previously been linked to high activity.
Nater, Darryl F.,Paul, Bhaskar,L?tsch, Lukas,Schrock, Richard R.,Copéret, Christophe
(2021)
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Reactions of α,β-Epoxysilanes with Grignard Reagents. Generation and Trapping of α-Trimethylsilyl Aldehydes and Ketones
α,β-Epoxysilanes react with Grignard reagents via initial rearrangement to generate α-silyl carbonyl compounds, which are trapped by the Grignard reagent to give β-hydroxysilanes. The reactions of epoxides 8 and 11 take place with very high stereoselectivity to form predominantly erythro β-hydroxysilanes 9 and 12, respectively, which undergo stereospecific β-elimination reactions to give either cis or trans olefins in 96-98percent isomeric purity.
Hudrlik, Paul F.,Hudrlik Anne M.,Misra, Raj N.,Peterson, David,Withers, Gregory P.,Kulkarni, Ashok K.
p. 4444 - 4448
(1980)
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Magnitude and consequences of or ligand σ-donation on alkene metathesis activity in d0 silica supported (≡SiO)W(NAr)(=CHtBu) (OR) catalysts
Well-defined silica supported W catalysts with the general formula [(SiO)W(NAr)(CHtBu)(OR)] (OR = OtBuF9, OtBuF6, OtBu F3, OtBu and OSi(OtBu)3), prepared by grafting bis-alkoxide complexes [W(NAr)(CHtBu)(OR)2] on silica dehydroxylated at 700 °C (SiO2(700)), display unexpectedly high activity in comparison to their Mo homologues. In this series, the activity of the self-metathesis of cis-4-nonene increases as a function of the OR ligand as follows: OtBu F3 3 F6 F9. In addition, the ratio of the two parent metallacyclobutane intermediates, trigonal bipyramidal (TBP)/square pyramidal (SP), which were formed by the metathesis of ethylene and observed by solid-state NMR, follows the same order: OtBu F3 3 F6 F9. This provides clear evidence of the decreasing σ-donating ability of the OR ligand with an increasing number of fluorine atoms and the positioning of a siloxy ligand in between OtBuF3 and OtBuF6. This study provides the first detailed structure-activity relationship analysis of a series of well-defined heterogeneous catalysts, showing that weaker σ-donor OR ligands lead to higher activity, and that the surface siloxy ligand is a rather small and weak σ-donor ligand overall, thus providing highly active yet stable catalysts. This journal is the Partner Organisations 2014.
Mougel,Coperet
p. 2475 - 2481
(2014)
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Cobalt Complexes of Bulky PNP Ligand: H2Activation and Catalytic Two-Electron Reactivity in Hydrogenation of Alkenes and Alkynes
The reactivity of cobalt pincer complexes supported by the bulky tetramethylated PNP ligands Me4PNPR(R = iPr, tBu) has been investigated. In these ligands, the undesired H atom loss reactivity observed earlier in some classical CH2-arm PNP cobalt complexes is blocked, allowing them to be utilized for promoting two-electron catalytic transformations at the cobalt center. Accordingly, reaction of the formally CoIMe complex 3 with H2 under ambient pressure and temperature afforded the CoIII trihydride 4-H, in a reaction cascade reasoned to proceed by two-electron oxidative addition and reductive eliminations. This mechanistic proposal, alongside the observance of alkene insertion and ethane production upon sequential exposure of 3 to ethylene and H2, prompted an exploration into 3 as a catalyst for hydrogenation. Complex 4-H, formed in situ from 3 under H2, was found to be active in the catalytic hydrogenation of alkenes and alkynes. The proposed two-electron mechanism is reminiscent of the platinum group metals and demonstrates the utility of the bulky redox-innocent Me4PNPR ligand in the avoidance of one-electron reactivity, a concept that may show broad applicability in expanding the scope of earth-abundant first-row transition-metal catalysis.
Fayzullin, Robert R.,Gallagher, James M.,Khaskin, Eugene,Khusnutdinova, Julia R.,Lapointe, Sébastien,Osborne, James,Pandey, Dilip K.
supporting information
p. 3617 - 3626
(2021/11/16)

Pd, Cu and Bimetallic PdCu NPs Supported on CNTs and Phosphine-Functionalized Silica: One-Pot Preparation, Characterization and Testing in the Semi-Hydrogenation of Alkynes
Triphenylphosphine stabilized Pd, Cu and PdCu nanocatalysts supported on carbon nanotubes (CNTs) or phosphorus functionalised silica (P?SiO2) were prepared via a one-pot methodology. The series of P?SiO2 supported catalysts evidenced metal particle sizes of metallic nanoparticles (M-NPs) between 1 and 2.4 nm, smaller than their equivalents on CNTs (2.4–2.6 nm). Such a difference in particle size as a function of the support and the metallic composition indicated the more pronounced mediation of the CNTs support during the formation of the M-NPs when compared to the P?SiO2 support. The series of supported catalysts were tested in the semi-hydrogenation of alkynes providing differences in reactivity which might be correlated with the size and composition of the M-NPs and the nature of corresponding support. The carbon supported catalysts displayed in general higher activities than those supported on silica and the bimetallic catalyst PdCu/CNTs were the most selective for the case of alkyl substituted alkynes. This catalyst could moreover be recycled several times without loss of activity nor selectivity.
Sánchez-Resa, Daniel,Delgado, Jorge A.,Fernández-Martínez, Maria Dolores,Didelot, Chloé,De Mallmann, Aimery,Szeto, Ka? C.,Taoufik, Mostafa,Claver, Carmen,Godard, Cyril
supporting information
p. 4970 - 4978
(2021/11/10)

Boosting the Metathesis Activity of Molybdenum Oxo Alkylidenes by Tuning the Anionic Ligand σ Donation
The catalytic performances of molecular and silica-supported molybdenum oxo alkylidene species bearing anionic O ligands [ORF9, OTPP, OHMT - where ORF9 = OC(CF3)3, OTPP = 2,3,5,6-tetraphenylphenoxy, OHMT = hexamethylterphenoxy] with different σ-donation a
De Jesus Silva, Jordan,Pucino, Margherita,Zhai, Feng,Mance, Deni,Berkson, Zachariah J.,Nater, Darryl F.,Hoveyda, Amir H.,Copéret, Christophe,Schrock, Richard R.
supporting information
p. 6875 - 6880
(2021/02/06)

Highly selective semi-hydrogenation of alkynes with a Pd nanocatalyst modified with sulfide-based solid-phase ligands
Soluble small molecular/polymeric ligands are often used in Pd-catalyzed semi-hydrogenation of alkynes as an efficient strategy to improve the selectivity of targeted alkene products. The use of soluble ligands requires their thorough removal from the reaction products, which adds significant extra costs. In the paper, commercially available, inexpensive, metallic sulfide-based solid-phase ligands (SPL8-4 and SPL8-6) are demonstrated as simple yet high-performance insoluble ligands for a heterogeneous Pd nanocatalyst (Pd@CaCO3) toward the semi-hydrogenation of alkynes. Based on the reactions with a range of terminal and internal alkyne substrates, the use of the solid-phase ligands has been shown to markedly enhance the selectivity of the desired alkene products by efficiently suppressing over-hydrogenation and isomerization side reactions, even during the long extension of the reactions following full substrate conversion. A proper increase in the dosage or a reduction in the average size of the solid-phase ligands enhances such effects. With their insoluble nature, the solid-phase ligands have the distinct advantage in their simple, convenient recycling and reuse while without contaminating the products. A ten-cycle reusability test with the SPL8-4/Pd@CaCO3 catalyst system confirms its well-maintained activity and selectivity over repeated uses. A mechanistic study with x-ray photoelectron spectroscopy indicates that the solid-phase ligands have electronic interactions with Pd in the supported catalyst, contributing to inhibit the binding and further reaction of the alkene products. This is the first demonstration of solid-phase ligands for highly selective semi-hydrogenation of alkynes, which show strong promise for commercial applications.
Huang, Lingqi,Hu, Kecheng,Ye, Ganggang,Ye, Zhibin
(2021/03/30)

Seed-mediated Growth of Alloyed Ag-Pd Shells toward Alkyne Semi-hydrogenation Reactions under Mild Conditions?
Ag@Ag-Pdx core-shell nanocomposites with various Ag/Pd ratio were deposited on Ag nanoplates using a seed growth method. When physically loaded on C3N4, Ag@Ag-Pd0.077/C3N4 with optimized Ag/Pd ratio could accomplish high catalytic performance for the semi-hydrogenation of phenylacetylene as well as other aliphatic (both terminal and internal alkynes) alkynes and phenylcycloalkynes containing functional groups (such as ester, hydroxyl, ethyl groups) under room temperature and 1 atm H2. The alloying and ensemble effects are used to interpret such catalytic performance.
Zheng, Yuqin,Tan, Taixing,Wang, Cheng
p. 3071 - 3078
(2021/09/13)

The role of CO2 in the dehydrogenation of n-octane using Cr-Fe catalysts supported on MgAl2O4
The effect of CO2 on the dehydrogenation of n-octane over Cr-Fe oxides supported on MgAl2O4 (MgAl) was investigated. Addition of Fe as a promoter facilitated the formation of Cr-O-Fe polymeric units, stabilizing the CrOx in the +3 state on the catalysts’ surface. Catalytic results revealed that the 2Cr-Fe catalyst was the most active and also stable (ca. 10 % CO2 conversion, 8 % n-octane conversion, 84 % selectivity to octene isomers) during a 30 h reaction. The stability and high octenes selectivity over this catalyst was reflected in its higher surface basicity. Based on a redox study using CO2, it was found that the dominant mechanism for CO2 activation was oxidative (Mars van Krevelen) over the monometallic Cr catalyst, while a non-oxidative (Reverse Water Gas Shift) mechanism applied over the nCr-Fe bimetallic catalysts. It is proposed that Cr-O-MgAl is the active site in the monometallic Cr catalyst, while the Cr-O-Fe polymeric units are the active sites in the bimetallic catalysts. Coke deposition was shown to be the major cause of deactivation of the catalysts.
Adam, Dailami S.,Bala, Muhammad D.,Friedrich, Holger B.,Mahomed, Abdul S.
(2021/08/09)

Ni-Catalyzed Isomerization-Hydrocyanation Tandem Reactions: Access to Linear Nitriles from Aliphatic Internal Olefins
A highly regioselective nickel-based catalyst system for the isomerization/hydrocyanation of aliphatic internal olefins is described. This benign tandem reaction provides facile access to a wide variety of aliphatic nitriles in good yields with excellent regioselectivities. Thanks to Lewis acid-free conditions, the protocol features board functional groups tolerance, including secondary amine and unprotected alcohol groups.
Gao, Jihui,Ni, Jie,Yu, Rongrong,Cheng, Gui-Juan,Fang, Xianjie
supporting information
p. 486 - 490
(2021/02/05)

ALCOHOL DEHYDRATION CATALYST, PREPARATION METHOD THE SAME AND METHOD FOR PREPARING ALPHA-OLEFINS USING THE SAME
The present invention relates to a catalyst for dehydration of a primary alcohol, a method of preparing the same, and a method of producing an alpha-olefin using the same. The catalyst for dehydration of a primary alcohol according to the present invention has an excellent catalyst stability while having an excellent activity with respect to dehydration, and a high turnover frequency, such that a linear alpha-olefin with high purity may be produced with a high selectivity even in a case where a relatively small amount of a cocatalyst is added as compared with a homogeneous catalyst system.
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(2020/11/24)

Efficient in situ palladium nano catalysis for Z-selective semi transfer hydrogenation of internal alkynes using safer 1, 4-butanediol
Simple and efficient in situ generated palladium nanoparticles (PdNPs) in PEG-4OO catalyzed semi transfer hydrogenation of internal alkynes to Z-alkenes with excellent selectivity along with the formation of beneficial γ-butyrolactone as a byproduct using low quantity of safer and attractive 1, 4-butanediol as a hydrogen source was described.
Rapeti, Siva Kumar,Kasina, Krishna Chaitanya,Gundepaka, Prasad,Birudaraju, Saritha,Sailaja
supporting information

(2019/12/09)

Accelerated Semihydrogenation of Alkynes over a Copper/Palladium/Titanium (IV) Oxide Photocatalyst Free from Poison and H2 Gas
Selective hydrogenation of alkynes to alkenes (semihydrogenation) without the use of a poison and H2 is challenging because alkenes are easily hydrogenated to alkanes. In this study, a titanium (IV) oxide photocatalyst having Pd core-Cu shell nanoparticles (Pd@Cu/TiO2) was prepared by using the two-step photodeposition method, and Pd@Cu/TiO2 samples having various Cu contents were characterized by electron transmission microscopy, X-ray photoelectron spectroscopy and UV-vis spectroscopy. Thus-prepared Pd@Cu/TiO2 samples were used for photocatalytic hydrogenation of 4-octyne in alcohol and the catalytic properties were compared with those of Pd/TiO2 and Cu/TiO2. 4-Octyne was fully hydrogenated to octane over Pd/TiO2 at a high rate and 4-octyne was semihydrogenated to cis-4-octene over Cu/TiO2 at a low rate. Rapid semihydrogenation of 4-octyne was achieved over Pd(0.2 mol%)@Cu(1.0 mol%)/TiO2, indicating that the Pd core greatly activated the Cu shell that acted as reaction sites. A slight increase in the reaction temperature greatly increased the rate with a suppressed rate of H2 evolution as the side reaction. Changes in the reaction rates of the main and side reactions are discussed on the basis of results of kinetic studies. Reusability and expandability of Pd@Cu/TiO2 in semihydrogenation are also discussed.
Imai, Shota,Nakanishi, Kousuke,Tanaka, Atsuhiro,Kominami, Hiroshi
p. 1609 - 1616
(2020/02/15)

Activation of Low-Valent, Multiply M-M Bonded Group VI Dimers toward Catalytic Olefin Metathesis via Surface Organometallic Chemistry
Olefin metathesis is a broadly employed reaction with applications that range from fine chemicals to materials and petrochemicals. The design and investigation of olefin metathesis catalysts have been ongoing for over half a century, with advancements made in terms of activity, stability, and selectivity. Immobilization of organometallic complexes onto solid supports such as silica or alumina is a promising strategy for catalyst heterogenization, often resulting in increased activity and stability. Consequently, a broad range of early transition metal catalysts bearing alkyl, oxide/alkoxide, and amide ligands have been grafted onto silica and their reactivities investigated. Herein, we report a series of silica-supported tungsten and molybdenum dimers (X3MMX3, where M = W and Mo; X = neopentyl, tert-butoxide, and dimethyl amide) and their reactivities toward catalytic olefin metathesis. Dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR), diffuse reflectance infrared Fourier transform (DRIFT), UV resonance Raman, and X-ray absorption (XAS) spectroscopies suggest that upon heterogenization the dimers bind to the surface in a monopodal fashion, with the MM triple bond remaining intact. These structural assignments were further corroborated by density functional theory (DFT) calculations. While the homogeneous dimer counterparts are inert, the supported low-valent alkyl W and Mo dimers become active for the disproportionative self-metathesis of propylene to ethylene and butenes and 4-nonene to 4-octene and 5-decene under mild conditions. The lack of activity observed for the free and supported tert-butoxide and dimethyl amide dimers likely suggests that the neopentyl groups are necessary for the formation of a putative alkylidene active species. The difference in reactivity between the free and supported dimers could be explained either by the lowering of the activation barrier of the complex through the electronic effects of the surface or by site isolation of catalytically relevant reactive intermediates.
Celik, Gokhan,Chapovetsky, Alon,Delferro, Massimiliano,Dogan, Fulya,Ferrandon, Magali S.,Kaphan, David M.,Khetrapal, Navneet,Kim, Hacksung,Kropf, A. Jeremy,Langeslay, Ryan R.,Perras, Frédéric A.,Pruski, Marek,Sattelberger, Alfred P.,Sharma, Prachi,Wegener, Evan C.,Wen, Jianguo,White, Jacob
supporting information
p. 1035 - 1045
(2020/05/04)

Selective hydrogenation of terminal alkynes over palladium nanoparticles within the pores of amino-modified porous aromatic frameworks
Palladium catalysts, based on porous aromatic frameworks, synthesized via Suzuki cross-coupling reaction and further modified with amino groups, were prepared and tested in hydrogenation of several unsaturated compounds. Catalysts obtained were characterized by several techniques including IR spectroscopy, solid-state NMR spectroscopy, low-temperature nitrogen adsorption, transmission electron microscopy, atomic emission spectroscopy and X-ray photoelectron spectroscopy. It was shown that the amino-groups within the structure of aromatic frameworks interact with palladium nanoparticles and enhance their selectivity towards hydrogenation of terminal alkynes.
Karakhanov, Edward,Maximov, Anton,Terenina, Maria,Vinokurov, Vladimir,Kulikov, Leonid,Makeeva, Daria,Glotov, Aleksandr
p. 176 - 184
(2019/05/24)

Constructing PtI?COF for semi-hydrogenation reactions of phenylacetylene
The great efforts have been devoted to fabricate excellent hydrogenation catalysts owing to the broad applications in industrial fields. However, the preparation processes of traditional hydrogenation catalysts are often complicated. Herein, mono-valence PtI?COF was synthesized as a catalyst for semi-hydrogenation of phenylacetylene for the first time. The easily prepared SO3H-linked COF possesses a two-dimensional eclipsed layered-sheet structure, making its incorporation with metal ions feasible. The as-prepared PtI?COF composite exhibits excellent performance for semi-hydrogenation phenylacetylene with 93.5% conversion and 90.2% selectivity to styrene under mild reaction conditions (1 ?bar H2, 25 ?°C) within 20 ?min. It's worth noting that the turnover frequency (TOF) value reaches at 3965 h-1, which outperforms most of recently reported excellent Pt-based catalysts for this reaction.
Li, Jian Hong,Yu, Zhi Wu,Li, Jian Qiang,Fan, Ya Ling,Gao, Zhi,Xiong, Jian Bo,Wang, Li,Tao, Yuan,Yang, Li Xiao,Xiao, Yu Xin,Luo, Feng
(2020/02/04)

Extension of surface organometallic chemistry to metal?organic frameworks: Development of a well-defined single site [(≡Zr? O?)W(=O)(CH2TBu)3] olefin metathesis catalyst
We report here the first step by step anchoring of a W(≡CtBu)(CH2tBu)3 complex on a highly crystalline and mesoporous MOF, namely Zr-NU-1000, using a Surface Organometallic Chemistry (SOMC) concept and methodology. SOMC allowed us to selectively graft the complex on the Zr6 clusters and characterize the obtained single site material using state of the art experimental methods including extensive solid-state NMR techniques and HAADF-STEM imaging. Further FT?IR spectroscopy revealed the presence of a W=O moiety arising from the in situ reaction of the W≡CtBu functionality with the coordinated water coming from the 8-connected hexanuclear Zr6 clusters. All the steps leading to the final grafted molecular complex have been identified by DFT. The obtained material was tested for gas phase and liquid phase olefin metathesis and exhibited higher catalytic activity than the corresponding catalysts synthesized by different grafting methods. This contribution establishes the importance of applying SOMC to MOF chemistry to get well-defined single site catalyst on MOF inorganic secondary building units, in particular the in situ synthesis of W=O alkyl complexes from their W carbyne analogues.
Thiam, Zeynabou,Abou-Hamad, Edy,Dereli, Busra,Liu, Lingmei,Emwas, Abdul-Hamid,Ahmad, Rafia,Jiang, Hao,Isah, Abdulrahman Adamu,Ndiaye, Papa Birame,Taoufik, Mostafa,Han, Yu,Cavallo, Luigi,Basset, Jean-Marie,Eddaoudi, Mohamed
supporting information
p. 16690 - 16703
(2020/11/09)

Carbonylative, Catalytic Deoxygenation of 2,3-Disubstituted Epoxides with Inversion of Stereochemistry: An Alternative Alkene Isomerization Method
Reactions facilitating inversion of alkene stereochemistry are rare, sought-after transformations in the field of modern organic synthesis. Although a number of isomerization reactions exist, most methods require specific, highly activated substrates to achieve appreciable conversion without side product formation. Motivated by stereoinvertive epoxide carbonylation reactions, we developed a two-step epoxidation/deoxygenation process that results in overall inversion of alkene stereochemistry. Unlike most deoxygenation systems, carbon monoxide was used as the terminal reductant, preventing difficult postreaction separations, given the gaseous nature of the resulting carbon dioxide byproduct. Various alkyl-substituted cis- A nd trans-epoxides can be reduced to trans- A nd cis-alkenes, respectively, in >99:1 stereospecificity and up to 95% yield, providing an alternative to traditional, direct isomerization approaches.
Lamb, Jessica R.,Hubbell, Aran K.,MacMillan, Samantha N.,Coates, Geoffrey W.
supporting information
p. 8029 - 8035
(2020/05/01)

Xanthate-mediated synthesis of (E)-alkenes by semi-hydrogenation of alkynes using water as the hydrogen donor
Semi-hydrogenation of alkynes is one of the most widely used methods for obtaining alkenes in laboratory preparation and in industry. Transition metal catalysts have been extensively studied for this transformation, but the tolerance of functional groups, such as pyridine,-OH,-NH2,-Bpin, and halides, and the toxicity of the trace amount of transition metal catalysts are still highly challenging. In this study, we report a general and robust strategy to achieve the semi-hydrogenation of alkynes using inexpensive and commercially available xanthate as the mediator. Mechanism studies support a non-radical process and H2O acts as the hydrogen donor.
Luo, Xianglin,Chen, Xiuwen,Chen, Lu,Zhang, Kun,Li, Yibiao
supporting information
p. 2170 - 2173
(2019/02/24)

Gem-Dialkyl Effect in Diphosphine Ligands: Synthesis, Coordination Behavior, and Application in Pd-Catalyzed Hydroformylation
A series of palladium complexes with C3-bridged bidentate bis(diphenylphosphino)propane ligands with substituents of varying steric bulk at the central carbon have been synthesized. The size of the gem-dialkyl substituents affects the C-C-C bond angles within the ligands and consequently the P-M-P ligand bite angles. A combination of solid-state X-ray diffraction (XRD) and density functional theory (DFT) studies has shown that an increase in substituent size results in a distortion of the 6-membered metal-ligand chair conformation toward a boat conformation, to avoid bond angle strain. The influence of the gem-dialkyl effect on the catalytic performance of the complexes in palladium-catalyzed hydroformylation of 1-octene has been investigated. While hydroformylation activity to nonanal decreases with increasing size of the gem-dialkyl substituents, a change in chemoselectivity toward nonanol via reductive hydroformylation is observed.
Aitipamula, Srinivasulu,Britovsek, George J. P.,Nobbs, James D.,Romain, Charles,Tay, Dillon W. P.,Van Meurs, Martin,White, Andrew J. P.
p. 663 - 671
(2020/01/02)

Porous organic polymer supported rhodium as a heterogeneous catalyst for hydroformylation of alkynes to α,β-unsaturated aldehydes
A new porous organic polymer supported rhodium catalyst (Rh/POL-BINAPa&PPh3) has been developed for the hydroformylation of various alkynes to afford the corresponding α,β-unsaturated aldehydes with high chem- and stereoselectivity, excellent catalytic activity and good reusability (10 cycles). The heterogeneous catalyst exhibited more catalytic activity than the comparable homogeneous Rh/BINAPa/PPh3 system.
Liang, Zuyu,Chen, Jianbin,Chen, Xin,Zhang, Kai,Lv, Jinhe,Zhao, Haowen,Zhang, Guoying,Xie, Congxia,Zong, Lingbo,Jia, Xiaofei
supporting information
p. 13721 - 13724
(2019/11/19)

Catalytic Azido-Hydrazination of Alkenes Enabled by Visible Light: Mechanistic Studies and Synthetic Applications
A visible-light-enabled catalytic intermolecular azido-hydrazination method for unactivated alkenes is developed via an orderly radical addition sequence. This transformation features metal-free and redox-neutral conditions and is applicable to a wide range of alkenes with commercially available reagents. Mechanistic and kinetic studies reveal that the efficient generation of azide radical enabled by fluorenone under visible-light is critical to this methodology. The β-azido alkyl hydrazines prepared with this reaction can be conveniently derived to valuable synthetic building blocks, and one of the products has been successfully applied in the total synthesis of (±)-ibrutinib, which is used to treat B cell cancers. (Figure presented.).
Wang, Peng,Luo, Yunxuan,Zhu, Songsong,Lu, Dengfu,Gong, Yuefa
supporting information
p. 5565 - 5575
(2019/11/14)

Vanadium-Catalyzed Cross Metathesis: Limitations and Implications for Future Catalyst Design
Self-metathesis of terminal olefins using vanadium(V) alkylidenes is presented. Under various reaction conditions, incomplete conversion is observed due to decomposition of the metallocyclobutane intermediate via β-hydride elimination. The activity was observed to decline when a more electron withdrawing, less sterically bulky ligand was used, in contrast to trends observed in ring-opening metathesis polymerization with vanadium catalysts. These results provide insight into the current limitations of olefin metathesis with vanadium catalysts, as well as guidance for catalyst development.
Farrell, Wesley S.
supporting information
p. 3481 - 3485
(2019/11/13)

Bis(bipyridine) ruthenium(ii) bis(phosphido) metalloligand: Synthesis of heterometallic complexes and application to catalytic (E)-selective alkyne semi-hydrogenation
The first phosphido derivative of the bis(bipyridine) ruthenium(ii) fragment, cis-[(bpy)2Ru(PPh2)2] ([RuP2]), has been developed and applied as a P-donor metalloligand to form new Ru-Rh, Ru-Ir and Ru2Cu2 heterometallic complexes. The Ru-Ir hydride complex [([RuP2])IrH(NCMe)3][BF4]2 exhibits significant catalytic activity for (E)-selective semi-hydrogenation of alkynes.
Takemoto, Shin,Kitamura, Manami,Saruwatari, Shuhei,Isono, Atsutaka,Takada, Yoko,Nishimori, Rie,Tsujiwaki, Mina,Sakaue, Naoki,Matsuzaka, Hiroyuki
supporting information
p. 1161 - 1165
(2019/01/28)

A General One-Pot Methodology for the Preparation of Mono- and Bimetallic Nanoparticles Supported on Carbon Nanotubes: Application in the Semi-hydrogenation of Alkynes and Acetylene
A facile and straightforward methodology for the preparation of monometallic (copper and palladium) and bimetallic nanocatalysts (NiCu and PdCu) stabilized by a N-heterocyclic carbene ligand is reported. Both colloidal and supported nanoparticles (NPs) on carbon nanotubes (CNTs) were prepared in a one-pot synthesis with outstanding control on their size, morphology and composition. These catalysts were evaluated in the selective hydrogenation of alkynes and alkynols. PdCu/CNTs revealed an efficient catalytic system providing high selectivity in the hydrogenation of terminal and internal alkynes. Moreover, this catalyst was tested in the semi-hydrogenation of acetylene in industrially relevant acetylene/ethylene-rich model gas feeds and showed excellent stability even after 40 h of reaction.
Lomelí-Rosales, Diego A.,Delgado, Jorge A.,Díaz de los Bernardos, Miriam,Pérez-Rodríguez, Sara,Gual, Aitor,Claver, Carmen,Godard, Cyril
supporting information
p. 8321 - 8331
(2019/06/04)

Mechanistic Study of a Re-Catalyzed Monoalkylation of Phenols
A mechanistic study of a rhenium catalyzed monoalkylation of phenols is described. Reaction kinetics reveals a zero-order dependence on both alkene and phenol and a half order dependence on catalyst. Isotopic labeling studies, competition experiments, kinetic isotope effects, and Hammett analysis together afford experimental data consistent with a reversible C-H activation step and an irreversible hydrometalation process. The turnover-limiting step is identified as catalyst deaggregation. NMR studies of binary mixtures of catalyst and a single substrate (alkene or phenol) as well as those of reaction mixtures identify potential intermediates and off-cycle species. Despite the numerous Re complexes formed in these mixtures, the overall reaction is both high yielding and highly selective for monoalkylation of phenols.
Lehnherr, Dan,Wang, Xiao,Peng, Feng,Reibarkh, Mikhail,Weisel, Mark,Maloney, Kevin M.
supporting information
p. 103 - 118
(2018/11/06)

Dendrimer-Encapsulated Pd Nanoparticles, Immobilized in Silica Pores, as Catalysts for Selective Hydrogenation of Unsaturated Compounds
Heterogeneous Pd-containing nanocatalysts, based on poly (propylene imine) dendrimers immobilized in silica pores and networks, obtained by co-hydrolysis in situ, have been synthesized and examined in the hydrogenation of various unsaturated compounds. The catalyst activity and selectivity were found to strongly depend on the carrier structure as well as on the substrate electron and geometric features. Thus, mesoporous catalyst, synthesized in presence of both polymeric template and tetraethoxysilane, revealed the maximum activity in the hydrogenation of various styrenes, including bulky and rigid stilbene and its isomers, reaching TOF values of about 230000 h?1. Other mesoporous catalyst, synthesized in the presence of polymeric template, but without addition of Si(OEt)4, provided the trans-cyclooctene formation with the selectivity of 90–95 %, appearing as similar to homogeneous dendrimer-based catalysts. Microporous catalyst, obtained only on the presence of Si(OEt)4, while dendrimer molecules acting as both anchored ligands and template, demonstrated the maximum activity in the hydrogenation of terminal linear alkynes and conjugated dienes, reaching TOF values up to 400000 h?1. Herein the total selectivity on alkene in the case of terminal alkynes and conjugated dienes reached 95–99 % even at hydrogen pressure of 30 atm. The catalysts synthesized can be easily isolated from reaction products and recycled without significant loss of activity.
Karakanov, Edward A.,Zolotukhina, Anna V.,Ivanov, Andrey O.,Maximov, Anton L.
p. 358 - 381
(2019/04/04)

Ultralow-content palladium dispersed in covalent organic framework for highly efficient and selective semihydrogenation of alkynes
Developing noble-metal-based catalysts with ultralow loading to achieve excellent performance for selective hydrogenation of alkynes under mild reaction conditions is highly desirable but still faces huge challenges. To this end, a SO3H-anchored covalent organic framework (COF-SO3H) as the support was deliberately designed, and then ultralow-content Pd (0.38 wt %) was loaded by a wet-chemistry immersion dispersion method. The resulting Pd0.38/COF-SO3H composite exhibits outstanding performance for the selective hydrogenation of phenylacetylene with 97.06% conversion and 93.15% selectivity to styrene under mild reaction conditions (1 bar of H2, 25 °C). Noticeably, the turnover frequency value reaches as high as 3888 h-1, which outperforms most of reported catalysts for such use. Moreover, such a catalyst also exhibits excellent activity for a series of other alkynes and high stability without obvious loss of catalytic performance after five consecutive cycles.
Li, Jian Hong,Yu, Zhi Wu,Gao, Zhi,Li, Jian Qiang,Tao, Yuan,Xiao, Yu Xin,Yin, Wen Hui,Fan, Ya Ling,Jiang, Chao,Sun, Li Jun,Luo, Feng
supporting information
p. 10829 - 10836
(2019/08/22)

Organoselenium-catalyzed enantioselective syn-dichlorination of unbiased alkenes
The enantioselective dichlorination of alkenes is a continuing challenge in organic synthesis owing to the limitations of selective and independent antarafacial delivery of both electrophilic chlorenium and nucleophilic chloride to an olefin. Development of a general method for the enantioselective dichlorination of isolated alkenes would allow access to a wide variety of polyhalogenated natural products. Accordingly, the enantioselective suprafacial dichlorination of alkenes catalyzed by electrophilic organoselenium reagents has been developed to address these limitations. The evaluation of twenty-three diselenides as precatalysts for enantioselective dichlorination is described, with a maximum e.r. of 76:24 Additionally, mechanistic studies suggest an unexpected Dynamic Kinetic Asymmetric Transformation (DyKAT) process may be operative.
Gilbert, Bradley B.,Eey, Stanley T.-C.,Ryabchuk, Pavel,Garry, Olivia,Denmark, Scott E.
supporting information
p. 4086 - 4098
(2019/06/25)

Well-Defined Rhodium-Gallium Catalytic Sites in a Metal-Organic Framework: Promoter-Controlled Selectivity in Alkyne Semihydrogenation to E-Alkenes
Promoters are ubiquitous in industrial heterogeneous catalysts. The wider roles of promoters in accelerating catalysis and/or controlling selectivity are, however, not well understood. A model system has been developed where a heterobimetallic active site comprising an active metal (Rh) and a promoter ion (Ga) is preassembled and delivered onto a metal-organic framework (MOF) support, NU-1000. The Rh-Ga sites in NU-1000 selectively catalyze the hydrogenation of acyclic alkynes to E-alkenes. The overall stereoselectivity is complementary to the well-known Lindlar's catalyst, which generates Z-alkenes. The role of the Ga in promoting this unusual selectivity is evidenced by the lack of semihydrogenation selectivity when Ga is absent and only Rh is present in the active site.
Desai, Sai Puneet,Ye, Jingyun,Zheng, Jian,Ferrandon, Magali S.,Webber, Thomas E.,Platero-Prats, Ana E.,Duan, Jiaxin,Garcia-Holley, Paula,Camaioni, Donald M.,Chapman, Karena W.,Delferro, Massimiliano,Farha, Omar K.,Fulton, John L.,Gagliardi, Laura,Lercher, Johannes A.,Penn, R. Lee,Stein, Andreas,Lu, Connie C.
supporting information
p. 15309 - 15318
(2018/11/30)

NCP ligand, [...] complex, synthesis method, intermediate and application
The invention discloses an NCP ligand, iridium complex, synthetic method, intermediate and application thereof. The invention provides an NCP ligand and an NCP ligand iridium complex, wherein R1, R2, R3, R4, R5, R6 and R7 separately represent hydrogen atom or C1-C30 alkyl, R' and R'' independently represent C1-C30 alkyl. The invention provides the application of the NCP ligand iridium complex to the catalysis of alkane dehydrogenation reaction, olefin isomerization reaction, alcohol dehydrogenation reaction, ester alpha alkylation reaction, and amide alpha alkylation reaction. The NCP ligand provided by the invention contains dialkyl substituted phosphine, which has strong electron donating ability and can form a NCP ligand iridium complex by complexing with iridium. The NCP ligand iridium complex uses pyridine to replace a conventional alkyl phosphate electron donor, and has the advantages of good stability, high selectivity on alkane dehydrogenation reaction, mild reaction conditions, good catalytic effect, and industrial production prospect.
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Paragraph 0103; 0197-0199

(2018/07/30)

Alkene Isomerization-Hydroboration Catalyzed by First-Row Transition-Metal (Mn, Fe, Co, and Ni) N-Phosphinoamidinate Complexes: Origin of Reactivity and Selectivity
We describe the results of our combined experimental and computational investigation of structurally analogous (N-phosphinoamidinate)metal(N(SiMe3)2) precatalysts ((PN)M; M = Mn2+, Fe2+, Co2+, and Ni2+ d5-d8) in the isomerization-hydroboration of 1-octene, cis-4-octene, or trans-4-octene (1a-c) with HBPin. As part of this investigation, the synthesis and crystallographic characterization of diamagnetic (PN)Ni, ((PN)NiH)2, (PN)NiH(L) (L = pyridine or DMAP), and (PN)Ni(NHdipp) (dipp = 2,6-iPr2C6H3) are reported. Divergent catalytic reactivity and selectivity was noted for members of the (PN)M series; (PN)Mn and (PN)Ni afforded poor hydroboration yields, whereas the use of (PN)Fe or (PN)Co afforded high conversion and selectivity for the terminal borylation product, (n-octyl)BPin (2a). DFT calculations involving (PN)M as well as stoichiometric reactivity studies featuring (PN)Ni confirmed that (PN)MH intermediates generated upon reaction of (PN)M with HBPin represent viable catalytic species whereby formation of putative (PN)Ni(H2BPin) is reversible. Conversely, poor catalytic performance was noted for ((PN)NiH)2 and (PN)NiH(L) (L = pyridine or DMAP). Using DFT calculations, the relative reactivity of (PN)M precatalysts was found to be a function of their spin-state energy gaps. For reaction of (PN)MnH with trans-4-octene (1c) there is no viable spin crossover mechanism and migratory insertion is slow, resulting in poor reaction yields. In contrast, (PN)FeH can access a lower barrier through spin crossover, whereas (PN)CoH has a very low migratory insertion barrier from its low spin state. While (PN)NiH has a reasonable migratory insertion barrier, it is plausible that off-catalytic cycle intermediates are responsible for the diminished reaction rate and product yields that are observed experimentally. On the basis of the computed isomerization and borylation energy landscapes, a Curtin-Hammett-type scenario with fast isomerization through β-hydride elimination and migratory insertion steps is proposed, giving rise to a catalytic equilibrium of isomeric (PN)M(octyl) resting states, followed by slow product-forming borylation. The significantly lower barriers calculated for borylation of terminal (PN)M(n-octyl) species versus isomeric internal (PN)M(CHR2) intermediates provides a rationale for the experimentally observed terminal isomerization-hydroboration selectivity.
Macaulay, Casper M.,Gustafson, Samantha J.,Fuller, Jack T.,Kwon, Doo-Hyun,Ogawa, Takahiko,Ferguson, Michael J.,McDonald, Robert,Lumsden, Michael D.,Bischof, Steven M.,Sydora, Orson L.,Ess, Daniel H.,Stradiotto, Mark,Turculet, Laura
p. 9907 - 9925
(2018/10/15)

Transition metal triflate catalyzed conversion of alcohols, ethers and esters to olefins
Herein, we report an efficient transition metal triflate catalyzed approach to convert biomass-based compounds, such as monoterpene alcohols, sugar alcohols, octyl acetate and tea tree oil, to their corresponding olefins in high yields. The reaction proceeds through C-O bond cleavage under solvent-free conditions, where the catalytic activity is determined by the oxophilicity and the Lewis acidity of the metal catalyst. In addition, we demonstrate how the oxygen containing functionality affects the formation of the olefins. Furthermore, the robustness of the used metal triflate catalysts, Fe(OTf)3 and Hf(OTf)4, is highlighted by their ability to convert an over 2400-fold excess of 2-octanol to octenes in high isolated yields.
Keskiv?li,Parviainen,Lagerblom,Repo
p. 15111 - 15118
(2018/05/04)

Highly β(Z)-Selective Hydrosilylation of Terminal Alkynes Catalyzed by Thiolate-Bridged Dirhodium Complexes
A series of novel monothiolate-bridged dirhodium complexes, [Cp Rh(μ-SR)(μ-Cl)2RhCp ][BF4] {Cp? = ??5-C5Me5, R = tertiary butyl (tBu), 1a; R = ferrocenyl (Fc), 1b; R = adamantyl (Ad), 1c} were designed and successfully synthesized, which can smoothly facilitate highly regioselective and stereoselective hydrosilylation of terminal alkynes to afford β(Z) vinylsilanes with good functional group compatibility. Furthermore, the hydride bridged dirhodium complex [Cp Rh(μ-StBu)(μ-Cl)(μ-H)RhCp ][BF4] (5) as a potential intermediate was obtained by the reaction of 1a with excess HSiEt3.
Zhao, Xiangyu,Yang, Dawei,Zhang, Yahui,Wang, Baomin,Qu, Jingping
supporting information
p. 5357 - 5361
(2018/09/13)

Olefin oligomerization via new and efficient Br?nsted acidic ionic liquid catalyst systems
Olefin oligomerization reaction catalyzed by new catalyst systems (a Br?nsted-acidic ionic liquid as the main catalyst and tricaprylylmethylammonium chloride as the co-catalyst) has been investigated. The synthesized Br?nsted acidic ionic liquids were characterized by Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV), 1H nuclear magnetic resonance (NMR), and 13C NMR to analyze their structures and acidities. The influence of different ionic liquids, ionic liquid loading, different co-catalysts, catalyst ratios (mole ratio of ionic liquid to co-catalyst), reaction time, pressure, temperature, solvent, source of reactants, and the recycling of catalyst systems was studied. Among the synthesized ionic liquids, 1-(4-sulfonic acid)butyl-3-hexylimidazolium hydrogen sulfate ([HIMBs]HSO4) exhibited the best catalytic activity under the tested reaction conditions. The conversion of isobutene and selectivity of trimers were 83.21% and 35.80%, respectively, at the optimum reaction conditions. Furthermore, the catalyst system can be easily separated and reused; a feasible reaction mechanism is proposed on the basis of the distribution of experimental products.
Wang, Guoqin,Song, Heyuan,Li, Ruiyun,Li, Zhen,Chen, Jing
p. 1110 - 1120
(2018/05/28)

Thermal, Catalytic Conversion of Alkanes to Linear Aldehydes and Linear Amines
Alkanes, the main constituents of petroleum, are attractive feedstocks for producing value-added chemicals. Linear aldehydes and amines are two of the most important building blocks in the chemical industry. To date, there have been no effective methods for directly converting n-alkanes to linear aldehydes and linear amines. Here, we report a molecular dual-catalyst system for production of linear aldehydes via regioselective carbonylation of n-alkanes. The system is comprised of a pincer iridium catalyst for transfer-dehydrogenation of the alkane using t-butylethylene or ethylene as a hydrogen acceptor working sequentially with a rhodium catalyst for olefin isomerization-hydroformylation with syngas. The system exhibits high regioselectivity for linear aldehydes and gives high catalytic turnover numbers when using ethylene as the acceptor. In addition, the direct conversion of light alkanes, n-pentane and n-hexane, to siloxy-terminated alkyl aldehydes through a sequence of Ir/Fe-catalyzed alkane silylation and Ir/Rh-catalyzed alkane carbonylation, is described. Finally, the Ir/Rh dual-catalyst strategy has been successfully applied to regioselective alkane aminomethylation to form linear alkyl amines.
Tang, Xinxin,Jia, Xiangqing,Huang, Zheng
supporting information
p. 4157 - 4163
(2018/03/29)

Thiol Treatment Creates Selective Palladium Catalysts for Semihydrogenation of Internal Alkynes
Surface and interfacial engineering of heterogeneous metal catalysts is effective and critical for optimizing selective hydrogenation for fine chemicals. By using thiol-treated ultrathin Pd nanosheets as a model catalyst, we demonstrate the development of stable, efficient, and selective Pd catalysts for semihydrogenation of internal alkynes. In the hydrogenation of 1-phenyl-1-propyne, the thiol-treated Pd nanosheets exhibited excellent catalytic selectivity (>97%) toward the semihydrogenation product (1-phenyl-1-propene). The catalyst was highly stable and showed no obvious decay in either activity or selectivity for over ten cycles. Systematic studies demonstrated that a unique Pd-sulfide/thiolate interface created by the thiol treatment was crucial to the semihydrogenation. The high catalytic selectivity and activity benefited from the combined steric and electronic effects that inhibited the deeper hydrogenation of C=C bonds. More importantly, this thiol treatment strategy is applicable to creating highly active and selective practical catalysts from commercial Pd/C catalysts for semihydrogenation of internal alkynes. The development of next-generation catalytic materials requires a methodological shift from trial-and-error to mechanism-directed design. It is highly desirable to build model catalyst systems with simplified structures to ensure maximized utilization of both state-of-the-art characterization tools and computational chemistry methods. In this work, thiol-treated palladium nanosheets are adopted as a model catalyst for the selective semihydrogenation of internal alkynes. Unexpectedly, thiol treatment created highly selective palladium catalysts with high activity toward the semihydrogenation reaction. The ultrathin nature of the as-prepared catalysts allows for the application of a variety of surface science and computational methods to resolve the complexity of metal-organic interfaces and thus elucidate the underlying mechanism. Driven by atomic-level understanding, we have realized practical, lead-free catalysts for semihydrogenation. Thiol treatment is demonstrated as a highly effective strategy for promoting the catalytic selectivity of Pd nanocatalysts in the hydrogenation of internal alkynes to alkenes.
Zhao, Xiaojing,Zhou, Lingyun,Zhang, Wuyong,Hu, Chengyi,Dai, Lei,Ren, Liting,Wu, Binghui,Fu, Gang,Zheng, Nanfeng
supporting information
p. 1080 - 1091
(2018/04/30)

COBALT COMPLEXES, PROCESS FOR PREPARATION AND USE THEREOF
The present invention discloses a cobalt compound of formula (I), a process for the preparation and use thereof. The present invention further relates to a pharmaceutical composition and a method inhibition of Tau Aggregation in a subject in need thereof using compound of formula (I).
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Page/Page column 15; 16

(2019/01/06)

Catalyst versus Substrate Control of Forming (E)-2-Alkenes from 1-Alkenes Using Bifunctional Ruthenium Catalysts
Here we examine in detail two catalysts for their ability to selectively convert 1-alkenes to (E)-2-alkenes while limiting overisomerization to 3- or 4-alkenes. Catalysts 1 and 3 are composed of the cations CpRu(κ2-PN)(CH3CN)+ and Cp?Ru(κ2-PN)+, respectively (where PN is a bifunctional phosphine ligand), and the anion PF6-. Kinetic modeling of the reactions of six substrates with 1 and 3 generated first- and second-order rate constants k1 and k2 (and k3 when applicable) that represent the rates of reaction for conversion of 1-alkene to (E)-2-alkene (k1), (E)-2-alkene to (E)-3-alkene (k2), and so on. The k1:k2 ratios were calculated to produce a measure of selectivity for each catalyst toward monoisomerization with each substrate. The k1:k2 values for 1 with the six substrates range from 32 to 132. The k1:k2 values for 3 are significantly more substrate-dependent, ranging from 192 to 62 000 for all of the substrates except 5-hexen-2-one, for which the k1:k2 value was only 4.7. Comparison of the ratios for 1 and 3 for each substrate shows a 6-12-fold greater selectivity using 3 on the three linear substrates as well as a >230-fold increase for 5-methylhex-1-ene and a 44-fold increase for a silyl-protected 4-penten-1-ol substrate, which are branched three and five atoms away from the alkene, respectively. The substrate 5-hexen-2-one is unique in that 1 was more selective than 3; NMR analysis suggested that chelation of the carbonyl oxygen can facilitate overisomerization. This work highlights the need for catalyst developers to report results for catalyzed reactions at different time points and shows that one needs to consider not only the catalyst rate but also the duration over which a desired product (here the (E)-2-alkene) remains intact, where 3 is generally superior to 1 for the title reaction.
Paulson, Erik R.,Delgado, Esteban,Cooksy, Andrew L.,Grotjahn, Douglas B.
supporting information
p. 1672 - 1682
(2019/01/04)

Direct Conversion of Alcohols into Alkenes by Dehydrogenative Coupling with Hydrazine/Hydrazone Catalyzed by Manganese
We have developed unprecedented methods for the direct transformation of primary alcohols to alkenes in the presence of hydrazine, and for the synthesis of mixed alkenes by the reaction of alcohols with hydrazones. The reactions are catalyzed by a manganese pincer complex and proceed in absence of added base or hydrogen acceptors, liberating dihydrogen, dinitrogen, and water as the only byproducts. The proposed mechanism, based on preparation of proposed intermediates and control experiments, suggests that the transformation occurs through metal–ligand cooperative N?H activation of a hydrazone intermediate.
Das, Uttam Kumar,Chakraborty, Subrata,Diskin-Posner, Yael,Milstein, David
supporting information
p. 13444 - 13448
(2018/09/14)

Effect of Carboxylate Ligands on Alkane Dehydrogenation with (dmPhebox)Ir Complexes
A series of carboxylate-ligated iridium complexes (dmPhebox)Ir(O2CR)2(H2O) (R = -CH3, -CH2CH3, -CMe3, -CH2C6H5, and -CH=CMe2) were designed and synthesized to understand the carboxylate ligand effects on the reactivity of the complex for alkane dehydrogenation. Kinetic studies showed that the different R groups of the carboxylate iridium complexes can affect the reactivity with octane in the β-H elimination step. The rate constants for octene formation with different carboxylate ligands follow the order R = -CH=CMe2 > -CMe3 > -CH2CH3 > -CH3 > -CH2C6H5. In contrast, there is no significant effect of carboxylate ligand on the rate of the C-H activation step at 160 °C. These experimental results support the findings in the previously reported density functional theory study of the (dmPhebox)Ir complex in alkane C-H activation.
Yuan, Hongmei,Brennessel, William W.,Jones, William D.
p. 2326 - 2329
(2018/03/13)

Ligand-free nickel-catalyzed semihydrogenation of alkynes with sodium borohydride: A highly efficient and selective process for: Cis -alkenes under ambient conditions
We report a low-cost and efficient catalytic system, involving in situ generated ligand-free Ni NPs, methanol and sodium borohydride, for the semihydrogenation of alkynes under ambient conditions. This catalytic system exhibits remarkably high activity, satisfactory cis-selectivity for internal alkynes, good stability and general applicability.
Wen, Xin,Shi, Xiaozhen,Qiao, Xianliang,Wu, Zhilei,Bai, Guoyi
supporting information
p. 5372 - 5375
(2017/07/06)

Phosphoramidite complexes of Pd(II), Pt(II) and Rh(I): An effective hydrosilylation catalyst of 1-hexyne and 1-octene
The hydrophosphorane HP(OC6H4NMe)2 was used to prepare the diastereotopic complexes [MCl2{P(OC6H4NMe)OC6H4NHMe}] (M?=?Pd, Pt) by reaction with [MCl2(PhCN)2], and [RhCl(PPh3){P(OC6H4NMe)OC6H4NHMe}] by reaction with [RhCl(PPh3)3]. To form these complexes, the phosphorane undergoes ring-opening, whereby it is coordinated as the tautomeric neutral phosphoramidite-amino chelating ligand. The crystal structure of [RhCl(PPh3){P(OC6H4NMe)OC6H4NHMe}] was determined and the geometry about the Rh(I) atom is square-planar with cis-disposed phosphorus-donor ligands. The Rh–P distance is shortened (2.1056(6) ?) due to Rh(d)?→?P π-backbonding. In addition, [RhCl(PPh3){P(OC6H4NMe)OC6H4NHMe}] was shown to be an effective regio- and stereoselective catalyst for the hydrosilylation of 1-octene and 1-hexyne.
Carroll, Hannah K.,Parlane, Fraser G.L.,Reich, Noah,Jelier, Benson J.,Montgomery, Craig D.
p. 78 - 83
(2017/06/13)

Intermetallic Pd1–Zn1 nanoparticles in the selective liquid-phase hydrogenation of substituted alkynes
A comparative study of the catalytic characteristics of monometallic Pd/α-Al2O3 and bimetallic Pd–Zn/α-Al2O3catalysts in the liquid-phase hydrogenation of structurally different substituted alkynes (terminal and internal, symmetrical and asymmetrical) was carried out. It was established that an increase in the reduction temperature from 200 to 400 and 600°C led to a primary decrease in the activity of Pd–Zn/α-Al2O3 due to the formation and agglomeration of Pd1–Zn1 intermetallic nanoparticles. The Pd–Zn/α-Al2O3 catalyst containing Pd1–Zn1 nanoparticles exhibited increased selectivity to the target alkene formation, as compared with that of Pd/α-Al2O3. Furthermore, the use of the Pd–Zn/α-Al2O3 catalyst made it possible to more effectively perform the kinetic process control of hydrogenation because the rate of an undesirable complete hydrogenation stage decreased on this catalyst.
Mashkovsky,Markov,Bragina,Rassolov,Baeva,Stakheev, A. Yu.
p. 480 - 491
(2017/08/08)

Multiple C-H Activations of Linear Alkanes by Various (??5-Cyclopentadienyl)W(NO)(CH2CMe3)2 Complexes
As illustrated in the accompanying diagram, thermolysis of Cp?W(NO)(CH2CMe3)2 (Cp? = n5-C5Me5) at 80 °C in neat linear alkanes effects three successive C-H bond activations of the hydrocarbon substrates and forms Cp?W(NO)(H)(n3-allyl) complexes in which the allyl ligands are derived from the alkanes. These allyl hydrido compounds exist in solutions as mixtures of isomers containing monosubstituted (i.e., terminal) or 1,3-disubstituted (i.e., internal) allyl ligands which can have either an endo or exo orientation with the substituent groups being either proximal or distal to the nitrosyl ligand. Due to steric factors the most abundant isomer in all cases has a monosubstituted allyl ligand in the endo orientation with the alkyl end distal to the nitrosyl ligand. In addition, the relative abundance of Cp?W(NO)(H)(n3-allyl) isomers having monosubstituted allyl ligands decreases with increasing length of the n-alkane chain. Further thermolysis of the Cp?W(NO)(H)(n3-allyl) complexes results in the liberation of alkenes. Whether initiated by Cp?W(NO)(CH2CMe3)2 or independently synthesized Cp?W(NO)(H)(n3-allyl) complexes, the n-alkane dehydrogenations generally result in the preferential formation of 1-alkenes. They are stoichiometric, and their outcomes are not significantly affected by varying the experimental conditions employed (e.g., time, temperature, an open system, use of an H2 acceptor, etc.) or by changing the initial bis(neopentyl) tungsten reactant to its CpEt (n5-C5Me4Et) and CpiPr (n5-C5H4iPr) analogues or to Cp?Mo(NO)(CH2CMe3)2. The results of DFT calculations are consistent with these dehydrogenations proceeding via 16e Cp?M(NO)(n2-alkene) (M = Mo, W) intermediates that are in equilibrium with their more stable 18e Cp?M(NO)(H)(n3-allyl) isomers. These intermediates facilitate the allyl ligand exchange reactions depicted in the accompanying diagram by functioning as internal hydrogen acceptors during the dehydrogenation of the linear alkanes. Thermolysis of the final hydrido allyl complexes liberates the desired alkenes.
Shree, Monica V.,Fabulyak, Diana,Baillie, Rhett A.,Lefèvre, Guillaume P.,Dettelbach, Kevan,Béthegnies, Aurélien,Patrick, Brian O.,Legzdins, Peter,Rosenfeld, Devon C.
supporting information
p. 2714 - 2726
(2017/08/21)

OLEFIN METATHESIS CATALYSTS
This invention relates generally to metathesis catalysts and the use of such catalysts in the metathesis of olefins and olefin compounds, more particularly, in the use of such catalysts in Z and E selective olefin metathesis reactions. The invention has utility in the fields of organometallics and organic synthesis.
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Page/Page column 78; 79

(2017/07/06)

Rhenium-catalysed hydroboration of aldehydes and aldimines
The first examples for the rhenium-catalysed hydroboration of aldehydes, ketones and aldimines, including heteroaromatic quinoline, are reported herein. Reactions are remarkably chemoselective and tolerant of several functional groups. A wide array of rhenium complexes were efficient pre-catalysts for these hydroborations, including new low-valent complexes of the formula [Re(N-N)(CO)3(L)]X (N-N = bipy derivative, L = labile ligand/solvent, and X = [BArF4]- and [B(3,5-di-tBu-cat)2]-), which have been characterized fully including an X-ray diffraction study for [Re(bipy)(CO)3(quin)][BArF4] (2). A new silver spiroboronate ester Ag[B(3,5-di-tBu-cat)2](NCCH3)3 (3) was prepared and characterized fully, including an X-ray diffraction study, and used to make one of the new rhenium complexes.
Arévalo, Rebeca,Vogels, Christopher M.,Macneil, Gregory A.,Riera, Lucía,Pérez, Julio,Westcott, Stephen A.
supporting information
p. 7750 - 7757
(2017/07/11)

One-step hydroprocessing of fatty acids into renewable aromatic hydrocarbons over Ni/HZSM-5: Insights into the major reaction pathways
For high caloricity and stability in bio-aviation fuels, a certain content of aromatic hydrocarbons (AHCs, 8-25 wt%) is crucial. Fatty acids, obtained from waste or inedible oils, are a renewable and economic feedstock for AHC production. Considerable amounts of AHCs, up to 64.61 wt%, were produced through the one-step hydroprocessing of fatty acids over Ni/HZSM-5 catalysts. Hydrogenation, hydrocracking, and aromatization constituted the principal AHC formation processes. At a lower temperature, fatty acids were first hydrosaturated and then hydrodeoxygenated at metal sites to form long-chain hydrocarbons. Alternatively, the unsaturated fatty acids could be directly deoxygenated at acid sites without first being saturated. The long-chain hydrocarbons were cracked into gases such as ethane, propane, and C6-C8 olefins over the catalysts' Br?nsted acid sites; these underwent Diels-Alder reactions on the catalysts' Lewis acid sites to form AHCs. C6-C8 olefins were determined as critical intermediates for AHC formation. As the Ni content in the catalyst increased, the Br?nsted-acid site density was reduced due to coverage by the metal nanoparticles. Good performance was achieved with a loading of 10 wt% Ni, where the Ni nanoparticles exhibited a polyhedral morphology which exposed more active sites for aromatization.
Xing, Shiyou,Lv, Pengmei,Wang, Jiayan,Fu, Junying,Fan, Pei,Yang, Lingmei,Yang, Gaixiu,Yuan, Zhenhong,Chen, Yong
p. 2961 - 2973
(2017/02/05)

Synthesis, characterization, and reactivities of molybdenum and tungsten PONOP pincer complexes
A new series of molybdenum and tungsten tricarbonyl pincer complexes, bearing pyridine-based PONOP-type pincer ligands, have been synthesized and fully characterized. Addition of HBF4·Et2O to these tricarbonyl complexes generated seven-coordinate molybdenum and tungsten hydride complexes, and these compounds have been isolated in good yields. These metal hydrides show fluxional behavior in solution. The hydride ligands on these metal complexes are acidic in nature and are readily deprotonated by bases. The molybdenum hydride complex is shown to catalyze isomerization of 1-hexene to internal isomers under mild conditions.
Castro-Rodrigo, Ruth,Chakraborty, Sumit,Munjanja, Lloyd,Brennessel, William W.,Jones, William D.
supporting information
p. 3124 - 3131
(2016/10/09)

PROCESS FOR DEHYDROGENATION OF ALKYL-CONTAINING COMPOUNDS USING MOLYBDENUM AND TUNGSTEN NITROSYL COMPLEXES
A process for the dehydrogenation of alkyl-containing compounds comprises reacting an alkyl-containing compound and a Group VI nitrosyl complex characterized as a transition metal complex having the composition Cp'M(NO)(R1)(R2), wherein Cp' is selected from certain substituted and unsubstituted η5-cyclopentadienyl groups; M is W or Mo; and R1 and R2 are independently selected from CH2C(CH3)3; CH2Si(CH3)3; CH2(C6H5); CH3; hydrogen; and η3-allyl; provided that if R1 is hydrogen, R2 is η3-allyl; under conditions such that the alkyl-containing compound is converted to an olefin, and in particular embodiments, a terminal olefin. The dehydrogenation can be carried out using a neat and/or undried alkyl-containing compound and/or may be conducted under air, and does not require a sacrificial olefin to drive the reaction, thereby increasing convenience and decreasing cost in comparison with some other dehydrogenation processes.
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(2016/08/10)

Cross-Linked "poisonous" Polymer: Thermochemically Stable Catalyst Support for Tuning Chemoselectivity
Designed catalyst poisons can be deliberately added in various reactions for tuning chemoselectivity. In general, the poisons are "transient" selectivity modifiers that are readily leached out during reactions and thus should be continuously fed to maintain the selectivity. In this work, we supported Pd catalysts on a thermochemically stable cross-linked polymer containing diphenyl sulfide linkages, which can simultaneously act as a catalyst support and a "permanent" selectivity modifier. The entire surfaces of the Pd clusters were ligated (or poisoned) by sulfide groups of the polymer support. The sulfide groups capping the Pd surface behaved like a "molecular gate" that enabled exceptionally discriminative adsorption of alkynes over alkenes. H2/D2 isotope exchange revealed that the capped Pd surface alone is inactive for H2 (or D2) dissociation, but in the presence of coflowing acetylene (alkyne), it becomes active for H2 dissociation as well as acetylene hydrogenation. The results indicated that acetylene adsorbs on the Pd surface and enables cooperative adsorption of H2. In contrast, ethylene (alkene) did not facilitate H2-D2 exchange, and hydrogenation of ethylene was not observed. The results indicated that alkynes can induce decapping of the sulfide groups from the Pd surface, while alkenes with weaker adsorption strength cannot. The discriminative adsorption of alkynes over alkenes led to highly chemoselective hydrogenation of various alkynes to alkenes with minimal overhydrogenation and the conversion of side functional groups. The catalytic functions can be retained over a long reaction period due to the high thermochemical stability of the polymer.
Yun, Seongho,Lee, Songhyun,Yook, Sunwoo,Patel, Hasmukh A.,Yavuz, Cafer T.,Choi, Minkee
p. 2435 - 2442
(2016/04/26)