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A part of this work was supported by the JSPS KAKENHI (grant number 19KK0126) and King Abdullah University of Science and Technology (KAUST) AMPM research center under collaborative funding. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract no. DE-AC02-76SF00515.

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...

A new dinuclear Pd(i) complex coordinating two bis(NHC) ligands revealed an unsuspected stability despite the unsaturation of the two metal centres. Even more surprisingly, the compound showed high and selective antiproliferative activity against different cancer cell lines and ovarian cancer tumoroids, and the mechanism of action was different from that of cisplatin.

Here we report a practical, highly enantioselective photoredox allylation of aldehydes mediated by chiral nickel complexes with commercially available allyl acetate as the allylating agent. The methodology allows the clean stereoselective allylation of aldehydes in good to excellent yields and up to 93 % e.e. using a catalytic amount of NiCl2(glyme) in the presence of the chiral aminoindanol-derived bis(oxazoline) as the chiral ligand. The photoredox system is constituted by the organic dye 3DPAFIPN and a Hantzsch's ester as the sacrificial reductant. The reaction proceeds under visible-light irradiation (blue LEDs, 456 nm) at 8–12 °C. Compared to other published procedures, no metal reductants (such as Zn or Mn), additives (e.g. CuI) or air-sensitive Ni(COD)2 are necessary for this reaction. Accurate DFT calculations and photophysical experiments have clarified the mechanistic picture of this stereoselective allylation reaction.

Secondary ligand–metal interactions are decisive in many catalytic transformations. While arene–gold interactions have repeatedly been reported as critical structural feature in many high‐performance gold catalysts, we herein report that these interactions can also be replaced by Au⋅⋅⋅H−C hydrogen bonds without suffering any reduction in catalytic performance. Systematic experimental and computational studies on a series of ylide‐substituted phosphines featuring either a PPh3 (PhYPhos) or PCy3 (CyYPhos) moiety showed that the arene‐gold interaction in the aryl‐substituted compounds is efficiently compensated by the formation of Au⋅⋅⋅H−C hydrogen bonds. The strongest interaction is found with the C−H moiety next to the onium center, which due to the polarization results in remarkably strong interactions with the shortest Au⋅⋅⋅H−C hydrogen bonds reported to date. Calorimetric studies on the formation of the gold complexes further confirmed that the PhYPhos and CyYPhos ligands form similarly stable complexes. Consequently, both ligands showed the same catalytic performance in the hydroamination, hydrophenoxylation and hydrocarboxylation of alkynes, thus demonstrating that Au⋅⋅⋅H−C hydrogen bonds are equally suited for the generation of highly effective gold catalysts than gold‐arene interactions. The generality of this observation was confirmed by a comparative study between a biaryl phosphine ligand and its cyclohexyl‐substituted derivative, which again showed identical catalytic performance. These observations clearly support Au⋅⋅⋅H−C hydrogen bonds as fundamental secondary interactions in gold catalysts, thus further increasing the number of design elements that can be used for future catalyst construction., Experimental and computational studies on PPh3 and PCy3‐substituted ylide‐functionalized phosphines as well as on a biaryl and a cyclohexyl‐aryl phosphine demonstrate that Au⋅⋅⋅H−C hydrogen bonds can serve as secondary metal ligand interactions similar to gold–arene interactions often used in ligand design for the stabilization of catalytically active species. Remarkably short Au−H bonds are observed.

Calculations were partially performed at the TUBITAK ULAKBIM, High Performance and Grid Computing Center (TRUBA resources) as well as the computational resources at CCBG (www.ccbg.chem.boun.edu.tr) funded by the Bogazici University Research Fund (BAP Project No: 5156 and BAP-SUP Project No: 8245). B.D thanks Gebze Technical University Research Fund (BAP Project No: 2018-A105-32) for the financial support. The authors thank Assist. Prof. Yunus Emre Turkmen (Bilkent University, Ankara, Turkey) for fruitful discussions

Computational screening of a series of aluminum complexes for their activity in the ring-opening transesterification polymerization (ROTEP) of e-caprolactone (CL) was performed using a “framework distortion energy” (FDE) hypothesis. An {N,N,N,N}-aluminum complex with a bis-indolide Schiff-base ligand was predicted on the basis of that screening to be an efficient catalyst, and this prediction was tested and verified experimentally through the synthesis and characterization of the complex and evaluation of its ROTEP reactivity.

We report on the facile conversion of [Pd-2(mu-Cl)(mu-eta(3)-R-allyl)(NHC)(2)] complexes, which are commonly considered undesirable off-cycle species in cross-coupling reactions, into active [PdCl(mu-Cl)(NHC)](2) pre-catalysts. All reactions proceed under mild conditions (40 degrees C, 1-2 hours in acetone) using inexpensive HCl as both an oxidant and chloride source. DFT calculations were performed to explore the possible mechanism of this transformation, which appears to involve a combination of two different pathways. Moreover this study provides insights into factors favoring and hindering Pd(i) dimer formation undesirable in catalysis.

We report here the first step by step anchoring of a W(≡C

A series of Cu(III)-OH complexes supported by differently substituted bis(carboxamido)pyridine ligands is modeled to identify factors affecting electronic structure and hydrogen atom transfer reactivity. Activation of hydrocarbon substrates is inferred to be influenced by a combination of many factors, including overall charge state, counterion nature (when present), solvation, attractive and repulsive steric interactions, and quantum mechanical tunneling along the reaction coordinate.

Density functional theory (DFT) is employed to characterize in detail the mechanism for the ring-opening polymerization (ROP) of ε-caprolactone catalyzed by iron alkoxide complexes bearing redox-active bis(imino)pyridine ligands. The combination of iron with the non-innocent bis(imino)pyridine ligand permits comparison of catalytic activity as a function of oxidation state (and overall spin state). The reactivities of aryl oxide versus alkoxide initiators for the ROP of ε-caprolactone are also examined. An experimental test of a computational prediction reveals an Fe(III) bis(imino)pyridine bis-neopentoxide complex to be competent for ROP of ε-caprolactone.

Selective decarbonylation of p-nitrophenol esters of fatty acids to the corresponding linear α-olefins (LAOs) was achieved using palladium catalysis. After extensive ligand screening, a mixed-ligand system exploiting the trans-spanning diphosphine XantPhos and an N-heterocyclic carbene (IPr) was identified as the most effective in yielding high α-selectivity and high conversions of the ester (>98% selectivity, >90% conversion using 2.5 mol % of PdCl2 and 5 mol % of the ligands, 190 °C, 2–2.5 h). On the basis of insights from modeling at the density functional level of theory, we propose that the mixed-ligand set achieves high α-selectivity by promoting olefin dissociation from the palladium center following β-hydride elimination, which is especially facilitated both by the combined steric bias of the mixed-ligand set and by the ability of the XantPhos ligand to coordinate in both mono- and bidentate fashions.

The reactivity of iron-based ring opening polymerization catalysts is compared when the catalyst is in three different oxidation states. Formally iron(i) monoalkoxide complexes 3a (p-methoxyphenoxide) and 3b (neopentoxide) supported by bis(imino)pyridine ligands were synthesized and investigated as catalysts for the ring opening polymerization and copolymerization of various monomers. For most monomers, 3a and 3b were superior catalysts compared to analogous, formally iron(ii) and iron(iii) complexes (1a/1b and 2a/2b, respectively) for the ring opening polymerization of various cyclic ester and cyclic carbonate monomers. Experimental and computational investigation into the electronic structures of 3a and 3b revealed that they are most accurately described as containing a high spin iron(ii) center that is antiferromagnetically coupled to a singly reduced bis(imino)pyridine ligand. This electronic structure leads to increased electron density near the metal center without modulating the apparent metal oxidation state, which results in superior catalytic performance for the more highly reduced 3a and 3b compared to the increasingly more oxidized complexes (i.e.1a/1b and 2a/2b, respectively) in ring opening polymerization reactions. These findings have significant ramifications for the emerging field of redox-switchable polymerization catalysis.

Combining high-throughput experimentation with conventional experiments expedited discovery of new first-row nickel catalysts for the dehydrative decarbonylation of the bioderived substrates hydrocinnamic acid and fatty acids to their corresponding alkenes. Conventional experiments using a continuous distillation process (180 °C) revealed that catalysts composed of NiII or Ni0 precursors (NiI2, Ni(PPh3)4) and simple aryl phosphine ligands were the most active. In the reactions with fatty acids, the nature of the added phosphine influenced the selectivity for α-alkene, which reached a maximum value of 94%. Mechanistic studies of the hydrocinnamic reaction using Ni(PPh3)4 as catalyst implicate a facile first turnover to produce styrene at room temperature, but deactivation of the Ni(0) catalyst by CO poisoning occurs subsequently, as evidenced by the formation of Ni(CO)(PPh3)3, which was isolated and structurally characterized. Styrene dimerization is a major side reaction. Analysis of the reaction mechanis...

All elementary steps in the mechanism of Pd-catalyzed decarbonylation of hydrocinnamic acid through formation of a mixed anhydride species have been characterized through electronic structure calculations. Oxidative addition of the mixed anhydride to a singly or doubly ligated Pd is followed by decarbonylation, alkene formation, and catalyst regeneration. Metal-assisted deprotonation of the alkyl-Pd species by a coordinated carboxylate is predicted to be the rate-determining step; theory suggests that bulkier phosphine ligands (e.g., P(o-Tol)3) reduce the free energy of activation substantially, while variation of the auxiliary anhydride has little influence on efficiency.

Copper is ubiquitous and its one-electron redox chemistry is central to many catalytic processes. Modeling such chemistry requires electronic structure methods capable of the accurate prediction of ionization energies (IEs) for compounds including copper in different oxidation states and supported by various ligands. Herein, we estimate IEs for 12 mononuclear Cu species previously reported in the literature by using 21 modern density functionals and the DLPNO-CCSD(T) wave function theory model; we consider extrapolated values of the latter to provide reference values of acceptable accuracy. Our results reveal a considerable diversity in functional performance. Although there is nearly always at least one functional that performs well for any given species, there are none that do so for every member of the test set, and certain cases are particularly pathological. Over the entire test set, the SOGGA11-X functional performs best with a mean unsigned error (MUE) of 0.22 eV. PBE0, ωB97X-D, CAM-B3LYP, M11-L, B3LYP, and M11 exhibit MUEs ranging between 0.23 and 0.34 eV. When including relativistic effects with the zero-order regular approximation, ωB97X-D, CAM-B3LYP, and PBE0 are found to provide the best accuracy.

The synthesis of a new potent strigolactone analogue (CISA-1), resulting in the formation of two interconverting structural isomers, which could not be identified, was recently reported. In the present study, a combined computational and experimental approach is used to identify the exact nature of these structural isomers. Although standard experimental techniques could not be used to determine the identity of the isomers, chromatographic methods excluded E/Z isomerisation. Computational H-1 NMR chemical shift values and DFT calculations on interconversion barriers strongly suggest that the CISA-1 isomers were interconverting (Z)-configured atropisomers.

Existing methods for preparing complex particles, i.e., hollow porous, depend on either multiple steps or a complex reactor design. Here, a straightforward method to prepare unique polymer particles with complex shapes via the use of simple equipment and readily available chemicals is reported. Beads, capsules, and rods with uniform size and interconnected pores are obtained through the formation of high internal phase emulsion (HIPE) droplets in a microfluidic channel. The method is applicable to a broad range of (meth)acralates. Controlling physical properties, such as viscosity and emulsion stability, is key to control the shape of the resulting particles. Post-modification of the particles via click chemistry, their application in liquid marble formation, and their use as droplet reactors are also demonstrated.

1,4-Cyclohexadiene (CHD) and 9,10-dihydroanthracene (DHA) are two substrates used to probe the steric requirements of metal-oxo oxidants in H-atom-transfer (HAT) reactions, based on the assumption that they have comparable C-H bond dissociation enthalpies (BDEs). We use computations to demonstrate that the BDE of DHA is ∼3.5 kcal mol(-1) larger than that of CHD and that their often comparable reactivity is based on a competing interplay of bond strengths and favorable van der Waals interactions.

The free-radical homopolymerization and copolymerization kinetics of styrene (ST) and 2-hydroxyethyl methacrylate (HEMA) in three different media (bulk, DMF, toluene) have been investigated by means of Density Functional Theory (DFT) calculations in combination with the Polarizable Continuum Model (PCM) and the Conductor-like Screening Model for Real Solvents (COSMO-RS). The conventional Transition State Theory (TST) is applied to calculate the rate parameters of polymerization. Calculated propagation rate constants are used to predict the monomer reactivity ratios, which are then used in the evaluation of the copolymer composition following the Mayo-Lewis equation. it is found that copolymerization reactions in bulk and toluene show similar transition geometries;, whereas, DMF has a tendency to form H-bonding interactions with the polar HEMA molecules, thus decreasing the reactivity of this monomer during homopolymerization and towards ST during copolymerization. Calculations of copolymer composition further show that the amount of HEMA monomer in the ST-HEMA copolymer system decreases in the polar DMF solution. The calculated spin densities of the radical species are in agreement with the rate parameters and confirm that the copolymerization propagation rate of the ST-HEMA system is in the order: k(p)(bulk) approximate to k(p)(toluene) > k(p)(DMF).