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This paper addresses a review of platinum-based hydrosilylation catalysts. The main field of application of these catalysts is the curing of silicone polymers. Since the 1960s, this area has developed rapidly in connection with the emergence of new polymer compositions and new areas of application. Here we describe general mechanisms of the catalyst activity and the structural effects of the ligands on activity and stability of the catalysts together with the methods for their synthesis.

First-row, earth-abundant metals offer an inexpensive and sustainable alternative to precious-metal catalysts. As such, iron and cobalt catalysts have garnered interest as replacements for alkene and alkyne hydrofunctionalization reactions. However, these have required the use of air- and moisture-sensitive catalysts and reagents, limiting both adoption by the non-expert as well as applicability, particularly in industrial settings. Here, we report a simple method for the use of earth-abundant metal catalysts by general activation with sodium tert -butoxide. Using only robust air- and moisture-stable reagents and pre-catalysts, both known and, significantly, novel catalytic activities have been successfully achieved, covering hydrosilylation, hydroboration, hydrovinylation, hydrogenation and [2 π +2 π ] alkene cycloaddition. This activation method allows for the easy use of earth-abundant metals, including iron, cobalt, nickel and manganese, and represents a generic platform for the discovery and application of non-precious metal catalysis. NaO t Bu — an alkoxide salt — enables simple access to low-oxidation-state catalysis using sustainable first-row transition metals (Fe, Co, Mn, Ni). The approach works across a wide range of reductive alkene and alkyne functionlization reactions including hydroboration, hydrosilylation, hydrogenation, hydrovinylation and [2 π +2 π ] cyclization reactions.

Alkene hydrosilylation is one of the most concise and atom-economical methods to synthesize organosilicon molecules. Herein, we reported the precise immobilization of metal single atoms (M-SAs; M = Ru, Rh, Ir, Pd, Pt, and Au) into a porphyrinic metal-organic framework (MOF) of PCN-222 (PCN = porous coordination network), and then applied the resultant MOF composites of M-SAs@PCN-222 to alkene hydrosilylation. Under solvent-free conditions, Pt-SAs@PCN-222 displayed an especially high catalytic efficiency with the turnover frequency up to 119 s −1 and the maximum turnover number of 906,250 at room temperature. Experimental and theoretical studies revealed that there existed strong interactions between Pt-SAs@PCN-222 and the substrates, which helped to condense the substrates in the cavities of the porous catalysts. Further density functional theory calculations and molecular dynamics simulations disclosed that PCN-222 could transfer electrons to Pt-SAs to enhance the silane oxidative addition and drive the reaction to proceed smoothly via Chalk–Harrod pathway.

Transition-metal-catalyzed alkene hydrosilylation is one of the most important homogeneous catalytic reactions, and the development of methods that use base metals, especially iron, as catalysts for this transformation is a growing area of research. However, the limited number of ligand scaffolds applicable for base-metal-catalyzed alkene hydrosilylation has seriously hindered advances in this area. Herein, we report the use of 1,10-phenanthroline ligands in base-metal catalysts for alkene hydrosilylation. In particular, iron catalysts with 2,9-diaryl-1,10-phenanthroline ligands exhibit unexpected reactivity and selectivity for hydrosilylation of alkenes, including unique benzylic selectivity with internal alkenes, Markovnikov selectivity with terminal styrenes and 1,3-dienes, and excellent activity toward aliphatic terminal alkenes. According to the mechanistic studies, the unusual benzylic selectivity of this hydrosilylation initiates from π – π interaction between the phenyl of the alkene and the phenanthroline of the ligand. This ligand scaffold and its unique catalytic model will open possibilities for base-metal-catalyzed hydrosilylation reactions. Hydrosilylation of alkenes poses substantial challenges in terms of regioselectivity. Here, the authors report iron complexes with 1,10-phenantroline ligand scaffolds which  display benzylic selectivity in the hydrosilylation of internal alkenes and Markovnikov selectivity with terminal styrenes and 1,3-dienes.

Transition-metal-catalysed, redox-neutral dehydrosilylation of alkenes is a long-standing challenge in organic synthesis, with current methods suffering from low selectivity and narrow scope. In this study, we report a general and simple method for the manganese-catalysed dehydrosilylation and hydrosilylation of alkenes, with Mn2(CO)10 as a catalyst precursor, by using a ligand-tuned metalloradical reactivity strategy. This enables versatility and controllable selectivity with a 1:1 ratio of alkenes and silanes, and the synthetic robustness and practicality of this method are demonstrated using complex alkenes and light olefins. The selectivity of the reaction has been studied using density functional theory calculations, showing the use of an iPrPNP ligand to favour dehydrosilylation, while a JackiePhos ligand favours hydrosilylation. The reaction is redox-neutral and atom-economical, exhibits a broad substrate scope and excellent functional group tolerance, and is suitable for various synthetic applications on a gram scale.Methods for the dehydrosilylation of alkenes typically suffer from low selectivity and narrow scope. Now, the highly selective manganese-catalysed redox-neutral dehydrosilylation and hydrosilylation of alkenes has been achieved through ligand-tuned metalloradical activity. Whereas an electron-rich bidentate ligand promotes dehydrosilylation, hydrosilylation is the favoured pathway when using an electron-deficient phosphine ligand. DFT calculations have been carried out to understand the observed selectivity.

Homogeneous noble metal catalysts used in alkene hydrosilylation reactions to manufacture organosilicon compounds commercially often suffer from difficulties in catalyst recovering and recycling, undesired disproportionation reactions, and energy-intensive purification of products. Herein, we report a heterogeneous 0.5Ru δ+ /ZrO 2 catalyst with partially charged single-atom Ru (0.5 wt.% Ru) supported on commercial ZrO 2 nanocrystals synthesized by the simple impregnation method followed by H 2 reduction. When used in the ethylene hydrosilylation with triethoxysilane to produce the desired ethyltriethoxysilane, 0.5Ru δ+ /ZrO 2 showed excellent catalytic performance with the maximum Ru atom utilization and good recyclability, even superior to homogeneous catalyst (RuCl 3 ·H 2 O). Structural characterizations and density functional theory calculations reveal the atomic dispersion of the active Ru species and their unique electronic properties distinct from the homogeneous catalyst. The reaction route over this catalyst is supposed to follow the typical Chalk—Harrod mechanism. This highly efficient and supported single-atom Ru catalyst has the potential to replace the current homogeneous catalyst for a greener hydrosilylation industry.

The addition of X 3 Si–H or X 2 B–H (X = H, OR or R) across a C–C multiple bond is a well-established method for incorporating silane or borane groups, respectively, into hydrocarbon feedstocks. These hydrofunctionalization reactions are often mediated by transition metal catalysts, with precious metals being the most commonly used owing to the ability to optimize reaction scope, rates and selectivities. For example, platinum catalysts effect the hydrosilylation of alkenes with anti-Markovnikov selectivity and constitute an enabling technology in the multibillion dollar silicones industry. Increased emphasis on sustainable catalytic methods and on more economic processes has shifted the focus to catalysis with more earth-abundant transition metals, such as iron, cobalt and nickel. This Review describes the use of first-row transition metal complexes in catalytic alkene hydrosilylation and hydroboration. Defining advances in the field are covered, noting the chemistry that is unique to first-row transition metals and the design features that enable them to exhibit precious-metal-like reactivity. Other important features, such as catalyst activity and stability, are covered, as are practical considerations, such as cost and safety. Transition-metal-catalysed hydrosilylation and hydroboration reactions are valuable in the synthesis of commodity and fine chemicals, respectively. This Review describes the catalyst design principles that enable us to perform these reactions using catalysts based on earth-abundant metals. Scenarios in which using earth-abundant metals can offer an advantage over using a precious metal are also outlined.

Hydrosilylation reactions, the (commonly) anti-Markovnikov additions of silanes to unsaturated bonds present in compounds such as alkenes and alkynes, offer numerous unique and advantageous properties for the preparation of polymeric materials, such as high yields and stereoselectivity. These reactions require to be catalyzed, for which platinum compounds were used in the initial stages. Celebrating the 50th anniversary of hydrosilylations in polymer science and, concomitantly, five decades of continuously growing research, hydrosilylation reactions have advanced to a level that renders them predestined for transfer into commercial products on the large scale. Facing this potential transfer, this review addresses and discusses selected current trends of the scientific research in the area, namely low-cost transition metal catalysts (focusing on iron, cobalt, and nickel complexes), metal-free catalysts, non-thermally triggered hydrosilylation reactions (highlighting stimuli such as (UV-)light), and (potential) industrial applications (highlighting the catalysts used and products manufactured). This review focuses on the hydrosilylation reactions involving alkene reactants.

Bringing silicon to life: Amino acids containing the element silicon were synthesized and demonstrated to undergo enzymatic transamination opening up broad perspectives for the biologization of silicon. This is illustrated by synthetic biologist Geppetto who watches in amazement as Silanocchio, his silicon‐based creation, comes to life. More information can be found in the Research Article by L. Fensterbank, P. Marliere and co‐workers. Artwork by Paola Olivares.

Desymmetrization of fully substituted carbons with a pair of enantiotopic functional groups is a practical strategy for the synthesis of quaternary stereocentres, as it divides the tasks of enantioselection and C−C bond formation. The use of disubstituted malonic esters as the substrate of desymmetrization is particularly attractive, given their easy and modular preparation, as well as the high synthetic values of the chiral monoester products. Here, we report that a dinuclear zinc complex with a tetradentate ligand can selectively hydrosilylate one of the carbonyls of malonic esters to give α-quaternary β-hydroxyesters, providing a promising alternative to the desymmetric hydrolysis using carboxylesterases. The asymmetric reduction features excellent enantiocontrol that can differentiate sterically similar substituents and high chemoselectivity towards the diester motif of substrates. Together with the versatile preparation of malonic ester substrates and post-reduction derivatization, the desymmetric reduction has enabled the synthesis of a diverse array of quaternary stereocentres with distinct structural features.The desymmetrization of easily accessible malonic esters represents an attractive approach towards the formation of chiral quaternary stereocentres, but is largely limited to enzymatic hydrolysis. Now, a zinc-catalysed asymmetric hydrosilylation reaction—that works with a broad scope of substrates—has been shown to reduce one of the esters to a primary alcohol with excellent enantiocontrol.