The present Review highlights the challenges and opportunities when using the combination CO2/H2 as a C1 synthon in catalytic reactions and processes. The transformations are classified according to ...the reduction level and the bond‐forming processes, covering the value chain from high volume basic chemicals to complex molecules, including biologically active substances. Whereas some of these concepts can facilitate the transition of the energy system by harvesting renewable energy into chemical products, others provide options to reduce the environmental impact of chemical production already in today's petrochemical‐based industry. Interdisciplinary fundamental research from chemists and chemical engineers can make important contributions to sustainable development at the interface of the energetic and chemical value chain. The present Review invites the reader to enjoy this exciting area of “catalytic chess” and maybe even to start playing some games in her or his laboratory.
The catalytic gambit: The combined use of CO2 and H2 as building blocks in catalytic processes provides access to products ranging from large volume base chemicals to highly functionalized complex molecules. The current state‐of‐the‐art is critically reviewed, highlighting pathways that are in line with “green chemistry” principles and offer the potential to harness renewable energy into the chemical value chain.
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The electrocatalytic transformation of carbon dioxide has been a topic of interest in the field of CO2 utilization for a long time. Recently, the area has seen increasing dynamics as an alternative ...strategy to catalytic hydrogenation for CO2 reduction. While many studies focus on the direct electron transfer to the CO2 molecule at the electrode material, molecular transition metal complexes in solution offer the possibility to act as catalysts for the electron transfer. C1 compounds such as carbon monoxide, formate, and methanol are often targeted as the main products, but more elaborate transformations are also possible within the coordination sphere of the metal center. This perspective article will cover selected examples to illustrate and categorize the currently favored mechanisms for the electrochemically induced transformation of CO2 promoted by homogeneous transition metal complexes. The insights will be corroborated with the concepts and elementary steps of organometallic catalysis to derive potential strategies to broaden the molecular diversity of possible products.
This review article illustrates and categorizes the currently favored molecular mechanisms for the electrochemically induced transformation of CO2 promoted by homogeneous transition metal complexes. The resulting insights are corroborated by the concepts and elementary steps of organometallic catalysis to derive strategies to broaden the molecular diversity of products.
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Designing for a green chemistry future Zimmerman, Julie B; Anastas, Paul T; Erythropel, Hanno C ...
Science (American Association for the Advancement of Science),
01/2020, Volume:
367, Issue:
6476
Journal Article
Peer reviewed
The material basis of a sustainable society will depend on chemical products and processes that are designed following principles that make them conducive to life. Important inherent properties of ...molecules need to be considered from the earliest stage-the design stage-to address whether compounds and processes are depleting versus renewable, toxic versus benign, and persistent versus readily degradable. Products, feedstocks, and manufacturing processes will need to integrate the principles of green chemistry and green engineering under an expanded definition of performance that includes sustainability considerations. This transformation will require the best of the traditions of science and innovation coupled with new emerging systems thinking and systems design that begins at the molecular level and results in a positive impact on the global scale.
The happy medium: A new catalytic pathway for the synthesis of the linear primary C8 alcohol products 1‐octanol and dioctyl ether from furfural and acetone has been developed using retrosynthetic ...analysis. This opens a general strategy for the synthesis of medium‐chain‐length alcohols from carbohydrate feedstock.
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CO2 conversion covers a wide range of possible application areas from fuels to bulk and commodity chemicals and even to specialty products with biological activity such as pharmaceuticals. In the ...present review, we discuss selected examples in these areas in a combined analysis of the state-of-the-art of synthetic methodologies and processes with their life cycle assessment. Thereby, we attempted to assess the potential to reduce the environmental footprint in these application fields relative to the current petrochemical value chain. This analysis and discussion differs significantly from a viewpoint on CO2 utilization as a measure for global CO2 mitigation. Whereas the latter focuses on reducing the end-of-pipe problem “CO2 emissions” from todays’ industries, the approach taken here tries to identify opportunities by exploiting a novel feedstock that avoids the utilization of fossil resource in transition toward more sustainable future production. Thus, the motivation to develop CO2-based chemistry does not depend primarily on the absolute amount of CO2 emissions that can be remediated by a single technology. Rather, CO2-based chemistry is stimulated by the significance of the relative improvement in carbon balance and other critical factors defining the environmental impact of chemical production in all relevant sectors in accord with the principles of green chemistry.
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While industrial NH3 synthesis based on the Haber–Bosch‐process was invented more than a century ago, there is still no molecular catalyst available which reduces N2 in the reaction system N2/H2 to ...NH3. As the many efforts of experimentally working research groups to develop a molecular catalyst for NH3 synthesis from N2/H2 have led to a variety of stoichiometric reductions it seems justified to undertake the attempt of systematizing the various approaches of how the N2 molecule might be reduced to NH3 with H2 at a transition metal complex. In this contribution therefore a variety of intuition‐based concepts are presented with the intention to show how the problem can be approached. While no claim for completeness is made, these concepts intend to generate a working plan for future research. Beyond this, it is suggested that these concepts should be evaluated with regard to experimental feasibility by checking barrier heights of single reaction steps and also by computation of whole catalytic cycles employing density functional theory (DFT) calculations. This serves as a tool which extends the empirically driven search process and expands it by computed insights which can be used to rationalize the various challenges which must be met.
Ok, computer: How can N2 be converted to NH3 by using H2 at a molecular catalyst? In this Concept article general insights are drawn from computational chemistry and a variety of intuition‐based concepts are presented with the intention to show how the problem can be approached systematically.
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Simply efficient: The homogenously catalyzed hydrogenation of CO2 to methanol is achieved by using a ruthenium phosphine complex under relatively mild conditions (see scheme; ...HNTf2=bis(trifluoromethane)sulfonimide). This is the first example of CO2 hydrogenation to methanol by using a single molecularly defined catalyst.
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The nonclassical ruthenium hydride pincer complex Ru(PNP)(H)2(H2) 1 (PNP = 1,3-bis(di-tert-butyl-phosphinomethyl)pyridine) catalyzes the anti-Markovnikov addition of pinacolborane to terminal alkynes ...yielding Z-vinylboronates at mild conditions. The complex Ru(PNP)(H)2(HBpin) 2 (HBpin = pinacolborane), which was identified at the end of the reaction and prepared independently, is proposed as the direct precursor to the catalytic cycle involving rearrangement of coordinated alkyne to Z-vinylidene as a key step for the apparent trans-hydroboration.
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The effective catalytic N‐methylation of anilines using CO2 as C1 source and molecular hydrogen as reducing agent was demonstrated using the well‐defined Ru(triphos)(tmm) catalyst. Secondary and ...primary (shown) aromatic amines were mono‐ or dialkylated, respectively, in high yields. N‐methylation of amides coupled with the amide hydrogenation offers an efficient approach to unsymmetrical tertiary methyl/alkyl/aromatic amines.
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A happy marriage of two processes: An effective catalytic system was identified for the direct synthesis of carboxylic acids from non‐activated olefins or alcohols, CO2, and H2. Detailed analysis ...together with labeling studies indicated that the overall hydrocarboxylation of simple olefins results from a combination of the reverse water–gas shift (rWGS) reaction and a hydroxycarbonylation step, each promoted by a rhodium catalyst (see scheme).
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