Two very rare cases of barium boryloxides, the homoleptic [Ba(OB{CH(SiMe3)2}2)2.C7H8] and the heteroleptic [{LONO4}BaOB{CH(SiMe3)2}2] stabilised by the multidentate aminoetherphenolate {LONO4}-, are presented, and their structural properties are discussed. The electron-deficient [Ba(OB{CH(SiMe3)2}2)2.C7H8] shows in particular resilient η6-coordination of the toluene molecule. Together with its amido parents [Ba{N(SiMe3)2}2.thf2] and [Ba{N(SiMe3)2}2]2, this complex catalyses the fast and chemoselective dehydrocoupling of borinic acids R2BOH and hydrosilanes HSiR'3, yielding borasiloxanes R2BOSiR'3 in controlled fashion. The assessment of substrate scope indicates that, for now, the reaction is limited to bulky borinic acids. Kinetic analysis was performed, showing that the rate-limiting step of the catalytic manifolds traverses a dinuclear transition state. A detailed mechanistic scenario is proposed on the basis of DFT computations, the results of which are fully consistent with experimental data. It consists of a stepwise process with rate-determining nucleophilic attack of a metal-bound O-atom onto the incoming hydrosilane, involving throughout dinuclear catalytically active species.

Single atom catalysis (SAC) is a recent discipline of heterogeneous catalysis for which a single atom on a surface is able to carry out various catalytic reactions. A kind of revolution in heterogeneous catalysis by metals for which it was assumed that specific sites or defects of a nanoparticle were necessary to activate substrates in catalytic reactions. In another extreme of the spectrum, surface organometallic chemistry (SOMC), and, by extension, surface organometallic catalysis (SOMCat), have demonstrated that single atoms on a surface, but this time with specific ligands, could lead to a more predictive approach in heterogeneous catalysis. The predictive character of SOMCat was just the result of intuitive mechanisms derived from the elementary steps of molecular chemistry. This review article will compare the aspects of single atom catalysis and surface organometallic catalysis by considering several specific catalytic reactions, some of which exist for both fields, whereas others might see mutual overlap in the future. After a definition of both domains, a detailed approach of the methods, mostly modeling and spectroscopy, will be followed by a detailed analysis of catalytic reactions: hydrogenation, dehydrogenation, hydrogenolysis, oxidative dehydrogenation, alkane and cycloalkane metathesis, methane activation, metathetic oxidation, CO2 activation to cyclic carbonates, imine metathesis, and selective catalytic reduction (SCR) reactions. A prospective resulting from present knowledge is showing the emergence of a new discipline from the overlap between the two areas.

The use of palladium(II) catalysts for the synthesis of aryl alkenes by addition of aromatic C–H bonds to alkynes has received a great interest in the literature. The mechanistic features of the reaction have been largely discussed, but no systematic study has been reported so far, particularly for what concerns the role of ligands. In this work, we performed a detailed theoretical study in order to fill this gap. To this extent, three different systems have been considered, with the aim to emphasize how the steric and electronic metal environment affects the catalytic activity and, most notably, steers the reaction selectivity toward the two main products of single and double alkyne insertion into the aromatic C–H bond. Moreover, given the crucial role of the acid media, two acids have been considered, namely, trifluoroacetic acid and tetrafluoroboric acid, to understand the effect of the acid strength and coordinative power on the competition between the different pathways.

The engineering of catalysts with desirable properties can be accelerated by computer-aided design. To achieve this aim, features of molecular catalysts can be condensed into numerical descriptors that can then be used to correlate reactivity and structure. Based on such descriptors, we have introduced topographic steric maps that provide a three-dimensional image of the catalytic pocket—the region of the catalyst where the substrate binds and reacts—enabling it to be visualized and also reshaped by changing various parameters. These topographic steric maps, especially when used in conjunction with density functional theory calculations, enable catalyst structural modifications to be explored quickly, making the online design of new catalysts accessible to the wide chemical community. In this Perspective, we discuss the application of topographic steric maps either to rationalize the behaviour of known catalysts—from synthetic molecular species to metalloenzymes—or to design improved catalysts.

Selective hydroamination of terminal alkynes with primary aryl amines is catalyzed by an unprecedented well-defined silica-supported tantalum complex [(≡Si-O-)Ta(η1σ-NEtMe)2(=NtBu)]. A molecular-level characterization of the surface organometallic Ta species was done with the help of characterization tech-niques including as in situ infrared, in situ elemental microanal-ysis, 1H and 13C solid-state NMR (including double and triple quanta sequence), and X-ray absorption spectroscopies. These were complemented by the state-of-the-art DNP-SENS 15N characterization. Several catalytic intermediates have been isolated in particular the 4-membered metallacycle ring inter-mediate resulting from the anti Markovnikov addition of the alkyne to the surface tantalum imido. The mechanism proposed was based on the isolation of all intermediates. A DFT calcula-tion has confirmed all the elementary steps and intermediates that were fully characterized.

The concept of upcycling postconsumer plastics into higher-value products is attractive, but the challenges remain to develop a cost-effective upcycling scheme, discover property-enhancing structures, and, most importantly, install recyclability into upcycled plastics to enable a circular lifecycle. Reported herein is a convenient and effective strategy to upcycle polyester, exemplified by poly(glycolic acid) (PGA), via transesterification (TEster) in bioderived, commercially available γ-butyrolactone (BL) that serves as both the solvent and comonomer, which generates sequence-defined copolymer poly(GA-co-BL). Owing to the isolated glycolic sequence present in the copolymer created uniquely by TEster, it exhibits much-enhanced thermal stability (≥44 °C) over both homopolymers or copolymers without such sequences. This upconverted copolymer is chemically recyclable, enabling a complete recovery of pure glycolic acid and BL feedstocks.

A combined experimental and theoretical study elucidates how Ni∙∙∙O neighboring group interactions drastically switch catalytic properties towards ethylene. A range of salicylaldiminato complexes with aryloxy groups in 2,6-position of the N-phenyl group were found to dimerize and oligomerize ethylene to butenes and branched oligomers (C4, C6, C8, C10…) in pressure reactor experiments, while corresponding reference catalysts with arylmethylene groups yield linear polyethylene with Mn 100.000 g mol-1. While both types of catalysts consume ethylene with similar high activities (105 turnovers h-1), the rate of ß-hydride elimination (BHE) is much increased for the case of aryloxy substitution. DFT studies show that formation of the relevant cis-agostic complex from which BHE occurs by displacement of ethylene from the cis-alkyl olefin complex is promoted by an Ni∙∙∙O interaction. This low energy pathway renders chain transfer competitive with insertion chain growth. The resulting Ni∙∙∙O intermediate is rather stable and similar in energy to key species of catalysis (ß-agostic and alkyl olefin complexes) but barely not yet an energetic sink that would impede catalysis.

A new class of [Au(NHC)(Bpin)] complexes has been synthesized and their unusual reactivity was investigated using computational and experimental methods. The gold-boryl complexes exhibit unexpected high stability and reactivity.

Carbon monoxide participates in many copper-catalyzed reactions, which makes CO-induced structural changes of Cu catalysts key for important industrial processes. We have studied the interaction of carbon monoxide with the Cu(100) single crystal termination at 120, 200, and 300 K by means of low energy electron diffraction (LEED), temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), polarization-modulation infrared reflection absorption spectroscopy (PM-IRAS), and density functional theory (DFT) calculations. The absorption band of CO (2082 to 2112 cm-1) at elevated gas pressure (up to 5 mbar) and at 200/300 K was found at higher wavenumber than the characteristic band of the c(2×2)CO structure, and was consistent with CO adsorbed on low-coordinated Cu atoms. The combined PM-IRAS/DFT analysis revealed that exposure to CO induces surface roughening through the formation of Cu adatoms and clusters on the (100) terraces. The roughened surface seemed surprisingly active for CO dissociation, which indicates its unique catalytic properties.

A simple and efficient catalyst, benzimidazole (BIMH)-modified copper foil, is developed to enhance the selective conversion of CO2 to C2/C3 products. The overall faradaic efficiency (FE) for CO2 reduction reaches 92.1% and the undesired hydrogen evolution reaction (HER) is lowered to a FE of 7% at -1.07 VRHE.