Production Of Isocyanates Research Articles

Green non<italic>-</italic>phosgene process for manufacturing isocyanates

Isocyanates are the core feed-stocks for the synthesis of polyurethane. At present, the industrial production of isocyanates mainly bases on the phosgene process, which is extremely toxic and yields large amounts of corrosive HCl. Non - phosgene process for isocyanates production is always one of the most important missions for green chemistry and related contents, and its implementation will bring about the revolutionary change for the polyurethane industry. This review focuses on the development of two-step route for aliphatic isocyanates in our lab as well as the existing problems, i.e., catalytic synthesis of N- substituted carbamates using various carbonyl sources, then thermal cracking target on isocyanate, especially for our strategy to the formation and depolymerization of the polymer derived from the thermal cracking process. Based on our research, a three-step non - phosgene process for isocyanate production is proposed, which provides a promissing technology for industrial application.

Flame retardancy and thermal decomposition behavior of TPU/chitosan composites

The application of chitosan (CS) in new materials is a hot research topic. In this paper, CS was used alone as flame retardant to prepare thermoplastic polyurethane elastomer (TPU) composites. Then, the flame retardancy and thermal decomposition behavior of TPU/CS composites were intensively investigated using cone calorimeter test (CCT), scanning electron microscope (SEM), microscale combustion colorimeter (MCC) test, thermogravimetric analysis/infrared spectrometry (TG‐IR), and gas chromatography‐mass spectrometry (GC‐MS). The results showed that CS can reduce the fire risk of TPU; 2.0‐wt% CS could make the peak value of heat release rate (pHRR) decreased to 457.2 kW/m2, reduced by 65.9% compared with TPU. And the peak value of smoke production rate (pSPR) and total smoke release (TSR) of the same sample was decreased by 79.4% and 54.2%, respectively. The TG‐IR and GC‐MS results confirmed that CS could promote TPU decomposition in advance, reacting with the decomposition products of TPU. Therefore, the production of combustible gas was reduced. The GC‐MS results showed that the production of isocyanates and ethers was reduced with the addition of CS. The digital photographs of SEM for the samples after CCT were shown that the char residue layer of the sample containing 2.0‐wt% CS was fibrous in shape. It could be speculated that the thermal decomposition products from TPU could react with CS at low temperature, which reduced the production of flammable gases. So CS had a good prospect in reducing the fire hazard for TPU.

Polyurethanes without Isocyanates and Isocyanates without Phosgene as a New Field of Green Chemistry: Mechanism, Catalysis, and Control of Reactivity

A brief review of studies in the kinetics, catalysis, and reaction mechanisms of new green chemistry processes for polyurethanes performed at the Semenov Institute of Chemical Physics of the Russian Academy of Sciences over the past decade and a half is given. The review centers on the formation of hydroxyurethanes without the use of isocyanates on the basis of the reaction of cyclic carbonates with amines, the phosgene-free production of isocyanates by thermal decomposition of acylazides, and the prospects for using renewable plant-based raw materials for the production of novel polyurethanes.

Characterization of Aerosol Release during Spraying of Isocyanate Products.

The aerosol release during the professional application of two different isocyanate based two component spray systems was identified and the physicochemical properties of the released airborne aerosols were characterized. For this purpose, aerosol release fractions were measured using a mass balance method described by Schwarz and Koch. Besides the release of total aerosol mass special emphasis was directed to the content of free monomeric MDI (4,4'- and 2,4'-diphenylmethane diisocyanate) in three particle size fractions relevant for inhalation uptake: inhalable, thoracic, and respirable size fraction. Two products were investigated: a two component PUR (polyurethane) spray foam (Elastopor) and a polyurea spray coating (Elastocoat). The mass fraction of the applied products released with the overspray as inhalable aerosol is 6.3 × 10-4 (Elastopor) and 4.0 × 10-4 (Elastocoat). Of the released total overspray aerosol 75 or 80% were in the thoracic size range, and 26 or 47% in the respirable regime for the PUR spray foam or the polyurea spray coating, respectively. At the time point of release the content of monomeric MDI in the aerosol corresponds to the composition of the bulk product. However, analysis of air samples indicates that <1% of the spray foam aerosol mass release fraction is attributed to free monomeric 4,4'- and 2,4'-MDI. For the Spray Coating the monomeric MDI fraction is <0.1%. Higher oligomers of MDI and prereacted oligomeric reaction products make up a few percent of the aerosol. This results in a total fraction of 0.0023% (spray foam) and 0.00015% (spray coating), respectively, of the sprayed monomeric MDI that is transferred into an inhalable aged aerosol. This data demonstrates, that during professional spraying only a small fraction of the total applied mass is released as airborne aerosol. The potential distribution of the theoretically inhalable aerosol in the respiratory tract and a low residual monomer content is described, significantly contributing to a refined safety assessment of the spray applications at the workplaces.

Получение толуилендиизоцианата с использованием бис(трихлорметил)карбоната

Toluelenediisocyanate – large-capacity reagent with a wide scope. The main quantity (85% of world production) of a toluelenediisocyanate is used for receiving polyurethane foam. The main way of receiving a toluelenediisocyanate is interaction of a toluelenediamine with carbonyl-chloride. If in the industry use of carbonylchloride as carbonylating agents have no difficulties, then in laboratory they exist. Carbonylchloride is inaccessible in the market. Usually it is received at the same enterprises at which further use. Now, as alternative and commercially available carbonylating agents, use bis(trichlormethyl)carbonate. Bis(trichlormethyl)carbonate a possibility of use in synthesis of aryldiisocyanates is directly connected with its physical properties, bis(trichlormethyl)carbonate represents steady crystal connection. Therefore its use in reaction of carbonylation of amines is more convenient, than gaseous carbonylchloride. There was a need for definition of optimum conditions of carrying out process of receiving this aryldiisocyanate with a satisfactory exit, because of inconsistency of references. For achievement of goals of a research – receiving a toluelenediisocyanate with use the bis(trichlorme-thyl)carbonate – we defined conditions of solubility of a toluelenediamine and the bis(trichlormethyl)carbonate in benzenechloride, influence of their molar ratio on an aryldiisocyanate exit is studied, also need of use of surplus is proved the bis(trichlormethyl)carbonate for suppression of course of collateral reactions. The offered method allows carrying out reaction to one stage, also to refuse low temperature at a stage of introduction of amine and it is essential to reduce synthesis time. This method can be used both in laboratory practice and in the production of isocyanates in industrial conditions.

Получение изоцианатов на примере бутилизоцианата термолизом карбаматов

Butyl isocyanate is widely distributed as a precursor for the production of a number of biologically active substances: fungicides, preservatives, insecticides, personal care products, etc. Nowadays, there are a number of methods for the preparation of isocyanates, which can be divided into liquid phase and gas phase. One of the perspective methods for the production of isocyanates is the thermolysis of carbamate and/or the actions of various reaction activating agents, accompanied by the elimination of alcohol, but this process is reversible, which greatly complicates its use in industry. The paper presents the results of studies of non-catalytic thermal decomposition of N-alkylcarbamates with the formation of alkylisocyanates on the example of butylisocyanate in the gas phase, flow reactor in a wide temperature range (200 to 450 °C). In addition, a series of experiments was carried out using a catalyst, dibutyltin dilaurate, in order to reduce the thermolysis temperature and increase the yield of the final product. To implement the isocyanate production process, an experimental laboratory setup, consisting of a gas flow meter (argon) regulator, a packed column (for heating) and a sorption solution tank, was developed and tested. The thermolysis of N-n-butylcarbamate was carried out in two variations: the preparation of an individual n-butylisocyanate and the passage of reaction products through a sorption solution linking the n-butyl isocyanate to N-n-butyl-N '-(1-phenylethyl)urea, which allows to estimate the yield of the target n-butylisocyanate without additional losses. The analysis of the obtained substances was carried out by high performance liquid chromatography with a UV detector (target product) and a mass detector (analysis of by-products). According to the results of research, a modification of the laboratory facility was proposed, as well as n-butylisocyanate was obtained with a yield of 49% on the basis of a new technique.

バイオマスイソシアネートを中心としたバイオマスポリウレタンの開発動向

The shift from petroleum based plastics to biomass based plastics is one solution that can’t be avoided forthe global warming issues by reduction of CO2 emission in recent years. In the polyurethane market, naturaloil (biomass) based polyols have been applied in this market for a long time. On the other hand, biomass basedisocyanates haven’t almost been commercialized and applied due to the difficulty of the molecular design ofisocyanate. In recent years, new biomass feedstock have been available for the production of isocyanates. Inthis review, we explain about the development of new biomass based polyurethanes centering on biomassbased isocyanates. 1,5-penthamethylete diisocyanate (1,5-PDI; STABiOTM PDITM) derived from L-lysine exhibitsimproved reactivity with alcohol compared to those of petroleum based 1,6-hexamethylene diisocyanate (HDI)and the other commercialized aliphatic and alicyclic isocyanates. In addition, the polyurethane coatings basedon 1,5-PDI derivatives shows improved chemical resistance and mechanical properties than those of HDI basedones.

Carbon2Polymer – Chemical Utilization of CO2 in the Production of Isocyanates

AbstractCO2 was investigated as carbon source for the synthesis of the polymer precursor toluene‐2,4‐diisocyanate (TDI). A four‐step synthesis was envisaged. The first step, i.e., the Ru‐catalyzed CO2 hydrogenation to [HCOOH·amine] adducts, was carried out under biphasic conditions allowing for straightforward reutilization of the catalyst phase. The investigation of the second step, the esterification of formic acid with methanol to yield methyl formate (MF), is ongoing with a strong focus on the integration with the hydrogenation step. The potential hazards of the third step, the Pd‐catalyzed oxidative carbonylation of toluene‐2,4‐diamine with MF, have been addressed developing a sophisticated protocol for a safe operation with organics/CO/O2 mixtures. For the final step, the carbamate cleavage of toluene‐2,4‐dicarbamate (TDC) towards TDI, monofunctional model substrates and TDC were cleaved in the presence of bifunctional catalysts. The obtained kinetic data allowed to implement the reaction in a continuous stirred‐tank reactor and will serve as starting point for further process optimization.

Metal modified fluorapatite (metal = Co, Ni, Cu, Zn): a new type of efficient catalyst for methyl N-phenyl carbamate direct synthesis from urea, methanol and aniline

The application of metal modified fluorapatite (metal-FAP, MCa9(PO4)6F2, M = Ca, Co, Ni, Cu, Zn) as highly efficient catalysts for the synthesis of an important intermediate methyl N-phenyl carbamate (MPC) for non-phosgene isocyanate production, from urea, methanol and aniline is reported firstly. The catalysts metal-FAP powders were synthesized by co-precipitation method and their properties were identified by ICP-AES, XRD, BET, TEM, EDS and NH3-TPD. Zn modified fluorapatite (ZnCa9(PO4)6F2, ZnFAP) with the strongest acidity among the metal-FAP (metal = Ca, Co, Ni, Cu, Zn) catalysts exhibited the highest catalytic activity to MPC formation. The effects of reaction temperature, time, molar ratio of raw materials, dosage of catalyst and reusability of the catalyst on the process were investigated. The optimal reaction parameters were determined as follows: aniline 20 mmol, the molar ratio urea/aniline 5:1, the molar ratio of methanol to aniline 20:1, ZnFAP 8.0 mmol, 6 h, 180 °C, with 94.4% aniline conversion and 75.8% selectivity to methyl N-phenyl carbamate. ZnFAP catalyst showed little catalytic activity loss after five times repeated use. The reaction mechanism is proposed and discussed.

Carbon2Polymer – Conceptual Design of a CO2‐Based Process for the Production of Isocyanates

AbstractThe capture of carbon dioxide and its utilization as a building block in chemical synthesis aim at reducing the depletion of fossil resources and the emission of greenhouse gases. The project Carbon2Chem®‐L5 is dedicated to the development of processes using CO2 for the production of polymer building blocks for polyurethanes. In this work, a process concept is presented for the CO2‐based synthesis of diisocyanates, the main starting material in polyurethane manufacture. Key parameters for process performance are discussed.

Spectroscopic Characterization of Model Compounds, Reactants, and Byproducts Connected with an Isocyanate Production Chain

Aromatic amines and amine hydrochloride salts play an important part in certain large-scale isocyanate production chains. For the first time, via a combination of periodic-DFT calculations, infrared spectroscopy, and inelastic neutron scattering, this work provides a comprehensive vibrational assignment of 4-benzylaniline (C6H4CH2C6H4NH2), 4,4′-methylenedianiline (H2NC6H4CH2C6H4NH2), and their associated amine hydrochloride salts. Deuterated analogues are additionally utilized to assist vibrational assignments. The heightened awareness of vibrational transitions for these technically relevant reagents and byproducts provides the opportunity to apply infrared spectroscopy as an in-line diagnostic tool within the industrial-scale process operation.

Air Liquide to build hydrogen plant in Korea

Air Liquide will spend $125 million to build a hydrogen plant for Kumho Mitsui Chemicals at the firm’s Yeosu industrial complex, South Korea’s largest isocyanate production site. The new steam methane reformer will increase capacity for hydrogen and carbon monoxide by 50% at the complex, where Kumho Mitsui also expects to boost output of isocyanate-based chemicals used to make polyurethane foam and rubber. Air Liquide expects to complete construction of the new reformer in 2020.

Why does 4-biphenyl carbonyl azide have ultra-short lived excited states? An ultrafast UV-vis spectroscopic and computational study.

Upon excitation at 308 nm, 4-biphenyl carbonyl azide (4-BpCON3) shows unusually fast decay of transient absorption associated with the first excited singlet state, with time constants of several ps in MeOH, acetonitrile, and CHCl3. In cyclohexane and cyclohexene, the lifetimes are ca. 0.3 ps, which is in stark contrast to the lifetimes of hundreds of ps in the case of 2-naphthoyl azide. Furthermore, photolysis at 266 and 308 nm brought about the same yields of nitrene and isocyanate products. To understand these findings, we also applied ultrafast transient absorption spectroscopy to the structurally related molecule, fluorene-2-carbonyl azide (F2CON3), in which the two phenyl rings are fixed in a plane by a methylene group. Both carbonyl azides (biphenyl and fluorenyl) have very short lived excited states in different solvents, indicating that the twisting of phenyl rings is not the reason for the fast decay. Theoretical studies using time dependent density functional theory (TDDFT), especially with PBE0 and CAM-B3LYP functionals, suggest that excited-state potential energy surface crossings lead to the efficient and fast decomposition of carbonyl azides upon photoexcitation. Especially, the decay of the Franck-Condon state to the S1 state with π(CON3)-π*(N3') transition character, where -N3 is in a bent conformation (∠NNN = ca. 125°), is the key step. Finally, a model is presented to explain solvent dependence, different decaying rates, and other experimental findings.

Alkyl Isocyanates via Manganese-Catalyzed C-H Activation for the Preparation of Substituted Ureas.

Organic isocyanates are versatile intermediates that provide access to a wide range of functionalities. In this work, we have developed the first synthetic method for preparing aliphatic isocyanates via direct C-H activation. This method proceeds efficiently at room temperature and can be applied to functionalize secondary, tertiary, and benzylic C-H bonds with good yields and functional group compatibility. Moreover, the isocyanate products can be readily converted to substituted ureas without isolation, demonstrating the synthetic potential of the method. To study the reaction mechanism, we have synthesized and characterized a rare MnIV-NCO intermediate and demonstrated its ability to transfer the isocyanate moiety to alkyl radicals. Using EPR spectroscopy, we have directly observed a MnIV intermediate under catalytic conditions. Isocyanation of celestolide with a chiral manganese salen catalyst followed by trapping with aniline afforded the urea product in 51% enantiomeric excess. This represents the only example of an asymmetric synthesis of an organic urea via C-H activation. When combined with our DFT calculations, these results clearly demonstrate that the C-NCO bond was formed through capture of a substrate radical by a MnIV-NCO intermediate.

Social aspects of water consumption: risk of access to unimproved drinking water and to unimproved sanitation facilities—an example from the automobile industry

The main aim of this study is to provide a methodology for assessing the social impacts related to water consumption in life cycle assessment (LCA). Methods for the environmental assessment of water use in LCA have already been developed. However, the impacts of water consumption from a social life cycle perspective, which are also site-dependent, still need to be addressed. According to a sustainability concept, freshwater sources should be assessed by considering the social and economic, as well as the environmental impacts. For the life cycle inventory (LCI) modelling, blue water flows from production processes are separated into direct process water and indirect water from energy production. Primary data, published studies and the GaBi 6© software’s Database serve as sources for this study. Risk of access to unimproved drinking water (RADW) and risk of access to unimproved sanitation facilities (RASA) are the social indicators selected for consumed water based on published data and according to the guidelines for social life cycle assessment (S-LCA). In the automobile industry, the social assessment is applied in the production stage of a conventional vehicle instrument panel. In order to show the influence of site-dependent aspects on these social indicators, three production sites (China, Germany and South Africa) are compared. The inventory is also used for an environmental assessment based on water stress indices (WSI), thereby confirming the compatibility of both social and environmental assessments. Results showed that the instrument panel manufactured in China is the most water-intensive alternative. Indirect water was the main driver for water consumption in all processes. The hotspots of water consumption are found in the supply chain processes, where isocyanate production embraces the most water-intensive processes. China is the country where the water consumed in the production processes by the manufacturer led to the highest risk of accessing unimproved drinking water and sanitation, i.e. not protected from contamination, for the local community. Of all processes, the amount of water consumed by the energy production processes was the highest. Thus, the instrument panel manufactured in China led to the highest environmental impact as well. A feasible and practicable method for a social risk assessment of freshwater consumption for automotive products is proposed. This contributes to the method development leading towards a comprehensive life cycle sustainability assessment (LCSA) of freshwater. The approach provides valid indicators for decision makers. Furthermore, the social assessment is implemented in an industrial product with a simplified supply chain. It has been shown that the social assessment is consistent with an existing environmental assessment, this being a first practical step for a sustainability assessment of water use for the automobile industry. The proposed method should be integrated in commercialised databases for assessments of an entire vehicle in order to facilitate its implementation. In addition, the economic pillar needs to be included for a comprehensive LCSA of water use. Further case studies should allow for a finer granularity in regional assessment, if required for the decision makers.

Important Green Chemistry and Catalysis: Non‐phosgene Syntheses of Isocyanates – Thermal Cracking Way

Currently, industrial production of isocyanates, or diisocyanates in particular, has been exclusively based on phosgene processes. Phosgene is extremely toxic and large amounts of corrosive HCl are produced as a side product. In the view of environment protection and society safety, development of non‐phosgene processes for isocyanates production will be highly desired, and this should be one of the most important missions for green chemistry and catalysis. In this review, efforts for development of non‐phosgene method for syntheses of isocyanates, i.e., catalytic syntheses of N‐substituted carbamates from nitro‐ or amino‐compounds with CO, dimethyl carbonate (DMC), urea and even CO2 etc. as carbonyl sources, then thermal cracking of N‐substituted carbamates to afford corresponding isocyanates, are summarized, and a brief prospect for non‐phosgene syntheses of isocyanates is also addressed.

Aliphatic isocyanurates and polyisocyanurate networks

The production, processing, and application of aliphatic isocyanate (NCO)‐based thermosets such as polyurethane coatings and adhesives are generally limited by the surprisingly high viscosity of tri‐functionality and higher‐functionality isocyanurates. These compounds are essential crosslinking additives for network formation. However, the mechanism by which these high viscosities are caused is not yet understood. In this work, model aliphatic isocyanurates were synthesized and isolated in high purity (&gt;99%), and their viscosities were accurately determined. It was shown that the presence of the NCO group has a strong influence on the viscosity of the system. From density functional theory calculations, a novel and significant bimolecular binding potential of −8.7 kJ/mol was identified between NCO groups and isocyanurate rings, confirming the important role of the NCO group. This NCO‐to‐ring interaction was proposed to be the root cause for the high viscosities observed for NCO‐functional isocyanurate systems. Molecular dynamics simulations carried out to further confirm this influence also suggest that the NCO‐to‐ring interaction causes a significant additional contribution to viscosity. Finally, model functional isocyanurates were further reacted into densely crosslinked polyisocyanurate networks which showed interesting material properties. Copyright © 2016 The Authors Polymers for Advanced Technologies published by John Wiley &amp; Sons, Ltd.

Lawrence R. Sita

Angewandte Chemie International EditionVolume 55, Issue 47 p. 14500-14500 Author ProfileFree Access Lawrence R. Sita First published: 08 June 2016 https://doi.org/10.1002/anie.201605082AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract “My motto is ‘There is no golden rule.’ I am waiting for the day when someone will discover instant coffee that tastes really really good ...” This and more about Lawrence R. Sita can be found on page 14500. Lawrence R. Sita The author presented on this page has recently published his 10th article in Angewandte Chemie in the last 10 years: “End-Group-Functionalized Poly(α-olefinates) as Non-Polar Building Blocks: Self-Assembly of Sugar–Polyolefin Hybrid Conjugates”: T. S. Thomas, W. Hwang, L. R. Sita, Angew. Chem. Int. Ed. 2016, 55, 4683; Angew. Chem. 2016, 128, 4761. Date of birth: August 6, 1959 Position: Professor, University of Maryland E-mail: lsita@umd.edu Homepage: http://www.chem.umd.edu/lawrence-r-sita/ ORCID: 0000-0002-9880-1126 Education: 1981 BS, Carnegie Mellon University, Pittsburgh 1986 PhD with Professor Satoru Masamune, Massachusetts Institute of Technology (MIT) 1986 Postdoctoral associate with Professor Richard R. Schrock, MIT Awards: 1995 Beckman Young Investigator Award; 1995 Camille Dreyfus Teacher-Scholar Award; 2004 NSF Special Creativity Award Current research interests: Inorganic and organometallic chemistry; polymer and material science; catalysis and new synthetic methods; self-assembly and nanofabrication Hobbies: Scuba diving, 3D modeling/printing, architecture My motto is “There is no golden rule.” I am waiting for the day when someone will discover instant coffee that tastes really really good. Chemistry is fun because we can still dream the seemingly impossible—and then make amazing discoveries while trying to achieve these goals. Looking back over my career, I am thankful for all my co-workers and their willingness to bring many oftentimes crazy ideas to fruition. The most significant historic event of the past 100 years was Edwin Hubble showing us that the universe is a lot bigger than we thought. In a spare hour, I plan for tomorrow, the next week, the next year, the next 10 years … My biggest inspiration is my wife and children. My favorite time of day is the break of dawn. My favorite way to spend a holiday is taking a very long and unscripted road trip. The secret of being a successful scientist is not giving up on any of your passions. In the future I see myself writing a memoir and science-fiction novels. My favorite author (science) is Stephen Jay Gould. The greatest scientific advance of the last decade was development of CRISPR/Cas9 gene editing. My 5 top papers: References 1“2,2,4,4,5,5-Hexakis(2,6-diethylphenyl)pentastanna[1.1.1]propellane: Characterization and Molecular Structure”: L. R. Sita, R. D. Bickerstaff, J. Am. Chem. Soc. 1989, 111, 6454. (The title molecule remains at the heart of questions regarding classical versus nonclassical bonding within main-group element frameworks.) 2“Tuning the Work Function of Gold with Self-Assembled Monolayers Derived from X−[C6H4−C≡C−]nC6H4−SH (n=0, 1, 2; X=H, F, CH3, CF3, and OCH3)”: R. W. Zehner, B. F. Parsons, R. P. Hsung, L. R. Sita, Langmuir 1999, 15, 1121. (Experimentally validated the concept of using SAMs to systematically modulate the energy barriers for electron and hole transport across interfaces.) 3“Stereospecific Living Ziegler–Natta Polymerization of 1-Hexene”: K. C. Jayaratne, L. R. Sita, J. Am. Chem. Soc. 2000, 122, 958. (A highly versatile platform for the living coordination polymerization of α-olefins.) 4“Highly Efficient, Living Coordinative Chain-Transfer Polymerization of Propene with ZnEt2: Practical Production of Ultrahigh to Very Low Molecular Weight Amorphous Atactic Polypropenes of Extremely Narrow Polydispersity”: W. Zhang, L. R. Sita, J. Am. Chem. Soc. 2008, 130, 442. (Presented the foundation for the large scale production of ‘precision’ polyolefins through living coordination polymerization of α-olefins.) 5“Metal-Mediated Production of Isocyanates, R3EN=C=O from Dinitrogen, Carbon Dioxide, and R3ECl”: A. J. Keane, W. S. Farrell, B. L. Yonke, P. Y. Zavalij, L. R. Sita, Angew. Chem. Int. Ed. 2015, 54, 10220; Angew. Chem. 2015, 127, 10358. (A complete chemical cycle for dinitrogen fixation.) Volume55, Issue47November 14, 2016Pages 14500-14500 ReferencesRelatedInformation

Metal‐Mediated Production of Isocyanates, R3ENCO from Dinitrogen, Carbon Dioxide, and R3ECl

AbstractA highly efficient and versatile chemical cycle has been developed for the production of isocyanates through the molecular fixation of N2, CO2 and R3ECl (E=C, Si, and Ge). Key steps include a ‘one‐pot’ photolytic NN bond cleavage of a Group 6 dinuclear dinitrogen complex with in situ trapping by R3ECl to provide a metal terminal imido complex that can engage in simultaneous nitrene‐group transfer and oxygen‐atom transfer to generate an intermediate metal terminal oxo complex with release of the isocyanate product. Reaction of the oxo complex with additional equivalents of R3ECl regenerates a metal dichloride that is the precursor for dinuclear dinitrogen starting material.

Metal-Mediated Production of Isocyanates, R3 EN=C=O from Dinitrogen, Carbon Dioxide, and R3 ECl.

A highly efficient and versatile chemical cycle has been developed for the production of isocyanates through the molecular fixation of N2 , CO2 and R3 ECl (E=C, Si, and Ge). Key steps include a 'one-pot' photolytic N-N bond cleavage of a Group 6 dinuclear dinitrogen complex with in situ trapping by R3 ECl to provide a metal terminal imido complex that can engage in simultaneous nitrene-group transfer and oxygen-atom transfer to generate an intermediate metal terminal oxo complex with release of the isocyanate product. Reaction of the oxo complex with additional equivalents of R3 ECl regenerates a metal dichloride that is the precursor for dinuclear dinitrogen starting material.