Stoichiometric Conditions Research Articles

Pr-rich cerium-zirconium-praseodymium mixed oxides for automotive exhaust emission control

This study describes the textural, structural, redox properties, oxygen reactivity of two Pr-rich cerium-zirconium-praseodymium (CZP) oxides (Ce0.45Zr0.10Pr0.45O2−x and Ce0.475Zr0.05Pr0.475O2−x) and their catalytic activity for propane and CO oxidation in both stoichiometric and lean conditions, two important reactions for automotive exhaust emission control. The concentration of oxygen vacancies can be tuned by the quantity of Pr3+ cations which depend both on the preparation method and the composition. The Pr4+(4 f1)/Pr3+(4 f2) ratio was accurately determined by magnetic measurement. A highly energetic grinding step was found to double this Pr3+ concentration, resulting in a strong enhancement of the low-temperature reducibility, bulk oxygen mobility and catalytic activity for propane deep oxidation. Pr-rich CZP oxides seem to be less relevant for CO oxidation, which is mainly driven by the specific surface areas. These Pr-rich CZP mixed oxides present better performances for lean conditions, suggesting their possible role in diesel oxidation catalysts applications.

Flame dynamics of premixed CH4/H2/air flames in a microchannel with a wall temperature gradient

The effect of hydrogen (H2) addition on the flame dynamics of premixed methane/air mixtures in a microchannel was investigated through two-dimensional numerical computations using a detailed chemistry model. Detailed numerical simulations were performed in a 2 mm diameter tube with 120 mm length and a hyperbolic wall temperature gradient condition. All numerical computations were performed at stoichiometric mixture conditions with a fixed inlet velocity of 15 cm/s. Flame repetitive extinction and ignition (FREI) has been observed to appear at various mixture conditions. The frequency of FREI shows a non-monotonic variation for CH4/air mixtures with H2 addition. The time taken for completion of one FREI cycle increases with H2 addition. The maximum temperature and heat of the reaction were observed to decrease with hydrogen addition. The effect of diameter on the FREI cycle was studied by comparing the numerical results for 1, 1.5, and 2 mm diameter tubes. As the diameter is reduced from 2 mm to 1 mm, the FREI frequency increased, and the maximum temperature decreased owing to increased heat loss through channel walls. The location of the ignition and extinction shifted downstream for 1 mm tube, as compared to a 2 mm diameter tube.

Effects of radiation reabsorption on the flame speed and NO emission of NH3/H2/air flames at various hydrogen ratios

Ammonia has attracted extensive attention in the direct combustion applications due to its carbon–neutral properties. In this study, the numerical simulations of NH3/H2/air one-dimensional premixed laminar flame under the stoichiometric condition with different H2 ratios (η = XH2/(XNH3 + XH2) = 0.2–0.7) were conducted to explore the influence of radiation reabsorption on laminar flame speed and NO emission. Also the effect of radiation reabsorption on NO generation and emission in NH3/H2/air mixture when η = 0.6 with different equivalence ratios was discussed. The results showed that the radiation reabsorption effect on flame speed decreased monotonically with the H2 ratio increasing from 0.2 to 0.7, and the maximum effect was 17%. The effect on flame speed was regulated by the combination of direct radiation effect and chemical effect, which was influenced by reaction R257 NH2 + NO = NNH + OH via OH radical when η = 0.2–0.7 and ϕ = 1.0. The promotion effect of radiation reabsorption on NO generation and emission decreased monotonically with the increasing H2 proportion. The enhancement of NO generation caused by radiation reabsorption was mainly controlled by R222 N + OH<=>NO + H. On the other hand, R220 N + NO<=>N2 + O, R240 NH + NO = N2O + H and R242 NH + NO = N2 + OH affected the NO emission in the post-flame zone. At η = 0.6 and ϕ = 0.65–1.5, the promotion of NO generation by radiation reabsorption was non-linear, which was mainly affected by R257, R241 NH + NO = N2O + H and R222 reactions. The NO emission was mainly influenced by R241 and R233 in the post-flame zone at ϕ = 0.65–1.05. And R241, R242, R256 NH2 + NO = N2 + H2O and R257 in the post-flame zone dominated the NO emission when ϕ > 1.05.

Shock tube study of natural gas oxidation at propulsion relevant conditions

Global climate change and rising crude oil prices have motivated search of clean, sustainable and economic fuel. Methane, having the highest hydrogen to carbon ratio is ideally the best option towards carbon neutral emissions and reduce greenhouse gas emissions. However, there the economic benefits are minimal when using pure methane because of purification costs. Natural gas primarily consists of methane but with appreciable amounts of C2C4 alkanes which significantly impact oxidation performance, especially when compared to pure methane at high pressures and temperatures, studies of natural gas have been scarce and there is new interest in studying natural gas for its application to propulsion devices. This single pulse shock tube study investigates the effect of natural gas composition on species yields as a function of temperature at various stoichiometric conditions (φ ≈ 0.5, 1.0, 2.0) and high pressure (240 atm) over a nominal reaction time of 2.5 ms. The experimentally measured speciation results for one real natural gas sample from Boise, ID (USA) and a reference natural gas sample are compared to species yield predictions using well established chemical kinetic mechanisms, to check the feasibility of using these mechanisms in the design of propulsion devices. The chemical kinetic simulations are carried out using the constant pressure approach as well as the changing pressure approach which considers the exact measured pressure change in the shock tube. The experiments provide a large speciation data set for optimizing chemical kinetic mechanisms for natural gas applications and to understand the effect of composition on natural gas chemical kinetics. The predictions vary significantly between models tested and effect of composition variation was evident. Aramco Mech 3.0 could predict the experiments almost perfectly, especially at fuel rich conditions.

Effects of porous materials with different thickness and obstacle layout on methane/hydrogen mixture explosion with low hydrogen ratio

The effects of porous materials with different thickness and obstacle layout on the explosion of 10%H2/90%CH4 at stoichiometric condition were studied. Three kinds of porous materials with different thickness were selected in the experiment, which are 1 cm, 2 cm and 3 cm respectively. Three kinds of obstacle layout were designed, which are symmetrical distribution, ipsilateral distribution and staggered distribution. Results show that porous materials with different thickness can promote or inhibit the explosion flame and overpressure when the obstacles are symmetrically distributed. The quenching failure of 1 cm thick porous material is similar to the action of mesh obstacles, which accelerates the flame to break through the bondage of porous material and continue to propagate, with a maximum speed of 87.74 m/s. When the thickness of porous material is 2 cm and 3 cm, the solid structure increases, the energy absorption increases, the flame impact porous materials quench, and the overpressure peak decreases. The greater the thickness of porous material, the better the attenuation effect, and the maximum overpressure attenuation can reach 59.71%. The change of obstacle layout has an important impact on the flame propagation structure. Compared with the ipsilateral distribution and staggered distribution, when the obstacles are symmetrically distributed, the vortex dynamic induced flame turbulence area is larger, the flame combustion rate is increased, and the explosion hazard is greater.

Mixture formation enhancement in a direct-injection spark-ignition engine using horizontal injection

In a direct-injection gasoline engine, combustion instability can increase because of the formation of an inhomogeneous mixture under stoichiometric conditions, a slow combustion rate under lean conditions, and misfires. Effective methods of dealing with combustion instability include enhancing tumble, increasing turbulence intensity, and enhancing stratification, and increasing flow velocity near the spark plug. Many studies have been conducted to enhance in-cylinder flows, but they have been limited to geometry modification or multi-injection. In this study, we adopt a horizontal injection strategy, as opposed to simple multiple injection in previous studies, to enhance in-cylinder flows. We examine the effect of horizontal injection on tumble by using a horizontal injector with an upward spray pattern and computational fluid dynamics. The tumble ratio and turbulence kinetic energy of the horizontal injector are compared to those of a conventional injector, which has a downward spray pattern. In addition, the effects of double injection on stratification and velocity near the spark plug at the end of compression are compared to that under single injection in terms of the equivalence ratio and average velocity near the spark plug. An injection pressure of 35 MPa is utilized. The total mass injected is 30 mg, and it is split into masses of 27 mg and 3 mg when using double injection. The CONVERGE v2.4 software application is used to reduce computational costs. The spray model is validated through a Schlieren visualization of the pent-roof combustion chamber, in which a high-temperature and high-pressure environment are simulated. The results indicate that horizontal injection enhances the tumble ratio and turbulence intensity by 22% and 26%, respectively, compared to those achieved with conventional, downward-spray injection. While double injection fails to enhance the tumble ratio and turbulence kinetic energy because the second injection mass is small, the velocity and stratification near the spark plug at the end of the compression strike are enhanced from −2 and 13.8 m/s to 11.5 and 18.6 m/s, respectively, because of double injection.

Experimental study on detonation propagation characteristics of hydrogen-nitrous oxide at stoichiometric and fuel-lean conditions

Knowledge of detonation propagation characteristics of H2–N2O mixtures is crucial for industrial safety and development. In this study, the detonation propagation characteristics of H2–N2O mixtures with different equivalence ratios (φ = 0.4, 0.6, and 1.0) in three tubes (d = 14.5, 19.5, and 28.6 mm) were investigated experimentally. Some dominant chemical lengths were evaluated together with cell size and normalized average velocity. The results show that the periodic oscillation of local velocity is more intense as approaching the limits. Below the limits, the detonation fails and decays rapidly to a “low velocity” regime. The tube scale and initial pressure determine the velocity deficit and the minimum detonation velocity shows no obvious trend on the mixture composition and tube scale. Scaling analysis illustrates that the dimensionless parameter d/ΔI and normalized average velocity show a single exponential growth trend. Notably, the detonation tends to decay earlier at φ = 1.0 than φ = 0.4 or φ = 0.6. Besides, fuel-lean mixtures (φ = 0.4 and 0.6) and stoichiometric mixtures (φ = 1.0) share similar critical pressure. It can be obtained that a linear relationship exists between the cell size and the induction length. The cell size data shows that the cell size of φ = 0.6 is the smallest, which agrees with the results of the induction length calculated. It is also demonstrated that the maximum value of heat release ratio peak is at φ = 0.6.

Micro-Explosion mechanism of iron hybrid Methane-Air premixed flames

Compared to gaseous hydrocarbon flame, a metal hybrid flame has higher energy and even has a higher flame temperature. This study explored the micro-explosion mechanisms of iron particles in methane-air premixed flames. Four different particle sizes were used in this experiment, that is 2–10 μm, 50 μm, 100 μm, and 150 μm. A conical methane-air premixed flame was fixed in a stoichiometric condition and doped with iron particles at various feeding rates. The 50- and 100-μm iron particles had a 20% and 500% higher micro-explosion probability than the 2–10-μm particles. The micro-explosion probability would increase with the increase of particle size. In addition, the micro-explosion probability of the 2–10 μm iron particles was 125% higher under 10% CO addition than under no CO addition. CO plays a critical role in increasing the micro-explosion probability of iron particles smaller than 50 µm.Regarding the mechanism of the micro-explosion of iron particles, the oxidizer diffuses into iron particles and produces iron oxide in a thin shell. However, limited oxygen heterogeneously reacts over the surface of the iron particles and produces Fe3O4. Fe3O4 comprises FeO and Fe2O3. However, when CO reacts Fe3O4, this reaction makes Fe3O4 redox into fresh Fe particles, whereas it will lead to FeO while Fe reacts with O2 predominantly. The presence of FeO brings about iron particles blinking and shrinking right after passing the flame front. When CO was dominated in the reaction, it gave rise to the formation of Fe(CO)5 gas bubbles in the film of iron particles. During the agglomeration of the bubbles, incorporating Fe(CO)5, CO, O2, and N2, the iron particles expand gradually and become hollow spherical particles eventually. However, under special conditions, this particle expansion will deteriorate the micro-explosion of the iron particles.

Arsenic removal using calcium hydroxyapatite synthesized from paper mill sludge

Calcium hydroxyapatite (Ca-HAp) was synthesized from calcium carbonate (CaCO3) extracted from a paper mill sludge. The extraction of CaCO3 was carried out by chemical precipitation process and synthesized to HAp nanoparticle under appropriate stoichiometric condition through wet chemical precipitation process. The size of the HAp nanoparticle was 42.5 nm under an optimized aging period of 24 h. This work aims in the batch adsorption of arsenic, an anionic metal arsenic in the form of Arsenite: As(III) on the synthesized Ca-HAp in laboratory scale. Batch kinetics studies were conducted for varying operational parameters such as temperature, initial adsorbate concentration, dye solution pH and rotation speed (RPM). In comparison with the two suggested isotherm models, Langmuir isotherm was suited to this adsorption process with a correlation coefficient of 0.92 and isotherm constant as 1.18 (KL). Chemisorption was found to be the rate-limiting mechanism for the sorption of arsenite onto Ca-HAp and thus followed pseudo-second-order kinetics. A maximum monolayer adsorption of 0.43 mg/g of arsenic was obtained at an equilibrium time of 60 min with 93% to 94.2% removal efficiency.

Mixing controlled compression ignition with methanol: An experimental study of injection and EGR strategy

Methanol is a fuel that can be produced using renewable electricity, green hydrogen, and a carbon-neutral carbon source. As a low-carbon liquid fuel, methanol is a leading candidate as a drop-in replacement fuel for rapid decarbonization of the transportation sector. In this work, methanol is tested experimentally in mixing-controlled compression ignition using a single-cylinder research engine. Specifically, the impact of a double injection strategy and high exhaust gas recirculation (EGR) dilution on performance and emissions parameters are studied. As a single-carbon, oxygenated fuel, methanol has a near-zero sooting potential, meaning there is no soot-NOx tradeoff as EGR dilution is increased. EGR dilution effectively reduces NOx emissions without a significant combustion efficiency or thermal efficiency penalty until the global equivalence ratio exceeds 0.9, at which point, a significant combustion efficiency penalty is incurred in the form of increased CO emissions. If stoichiometric operation with high EGR dilution is considered, engine-out NOx emissions are low, even at very high loads, and NOx aftertreatment is simplified through the use of a three-way catalyst. However, a relative decrease in the net fuel conversion efficiency of up to 8.5% was observed, demonstrating an emissions-efficiency tradeoff. Under lean and stoichiometric conditions, no appreciable agglomeration of particulate matter was observed.

Experimental study on multi-channel ignition of propane-air by transient repetitive nanosecond surface dielectric barrier discharge

Multi-channel ignition by nanosecond surface dielectric barrier discharge (nSDBD) offers potential for efficiency boost in spark ignition engines. In this paper, transient repetitive nSDBD ignition is proposed using a simple pulse forming circuit to make multi-channel ignition more feasible, considering that nSDBD can be enhanced by high frequency pulses and that convenient discharge energy control can be achieved by adjusting pulse number. Ignition experiments for propane/air mixtures were carried out in a constant volume combustion chamber under stoichiometric conditions at ambient initial temperature and pressure. Discharge channel transformation and flame propagation were captured by a high-speed camera. For 20 kHz negative pulses, discharge energy rose from 4 mJ to 8 mJ as pulse number increases from 1 to 12, and filaments grew from 2 mm to 12 mm. Partially overlapping filaments formed a tree-like discharge pattern with divergent roots and a concentrated middle part. Multiple flame kernels were generated in the middle region of the filaments and then greatly promoted by subsequent discharges, resulting in a petaloid flame. Ignition probability has been tested and the minimum ignition energy of repetitive nSDBD is obtained. The influence of discharge energy on flame propagation speed and combustion characteristics were analyzed.

Numerical assessment of interchangeability potential for syngas-fueled rotary engine

The syngas-fueled rotary engine can be considered as a promising solution for small–scale decentralized power generation due to high specific power, engine simplicity, smoothness and a low tendency for abnormal combustion. Since the decisive feature of syngas refers to feedstock flexibility, in this study we consider syngas with various compositions, produced from biomass, coal and natural gas, as a primary fuel for rotary engines. It was shown that rotary engine performance, efficiency and emission are mostly affected by the balance between combustion promoters and diluents in the air-syngas mixture. Particularly, high hydrogen concentration and lower inert content result in maximum power, heat release and thermal efficiency for stoichiometric and lean conditions. For the rotary engine with a homogeneous charge of the fuel, the combustion process is characterized by the weak influence of turbulence, while the laminar flame speed is an influential parameter in combustion behavior. The high magnitude of specific fuel consumption makes it difficult for engine operation at lean conditions. Although, the lean mixture cannot provide enough high flame temperature for NOx formation. The CO2 emission is affected by the hydrogen to carbon ratio. The opposite trend is observed between NOx and CO emission pathways due to oxygen availability. The power generation system based on the syngas-fueled rotary engine with syngas produced by not only well-known technology such as gasification or steam reforming but novel concepts (non-catalytic partial oxidation) can provide sustainability to the energy sector and reduce consumption of fossil fuels..

Ignition timing effect on the combustion performance of hydrogen addition in methane fermentation gas in a local energy system

Nowadays, the reduction in carbon emission becomes the big issue in the world. In order to achieve the target of “carbon neutral” in the middle of 21st century, a regional energy system is designed to develop a carbon recycle system with the help of fermented gaseous fuels for electric power generation. Hydrogen (H2) addition is widely used for methane (CH4) combustion to improve the engine efficiency. However, less attention was paid on the various ignition timing for the maximum brake torque (MBT) and brake thermal efficiency (BTE) at a certain power output. In order to check the ignition timing effect on CH4 combustion with H2 addition, experiments were performed in a spark ignition engine with engine speed fixed on 1500 revolutions per minute (rpm). Firstly, CH4 was only used for combustion with excess air ratio (λ) changing from 1.01 to 1.42. Then, H2 was added with volume percentage varying from 10% to 50%. Among these discussions, torque, brake mean effective pressure (BMEP), BTE and brake specific fuel consumption (BSFC) were evaluated. Based on the results, high efficiency can be achieved by advancing the ignition timing when CH4 only at larger λ. When H2 added, the ignition timing should be retarded to obtain higher BTE from 10 % to 50 % H2 addition. Under the lean-burn condition, through delaying the ignition timing at −15° CA TDC, BTE of 50% H2 addition reaches to 22%, which is even higher than that of CH4 only combustion at stoichiometric condition. Furthermore, working and optimal regions for the co-combustion of H2 and CH4 are mapped under various conditions.

Pulsating one-dimensional detonation in ammonia-hydrogen–air mixtures

In this study, one-dimensional detonations in ammonia/hydrogen-air mixtures are numerically investigated by solving the fully compressible Navier-Stokes equations with detailed chemistry. Pulsating instabilities with single-mode are observed during the detonation wave propagation, accompanied by periodic coupling and decoupling of the lead shock wave and the reactive front. The ratio between driver pressure and initial pressure determines the overdrive degree and thus the oscillatory mode of detonation for a premixture with certain composition. The effects of hydrogen dilution and mixture equivalence ratio on pulsating detonations are also examined under a constant driver pressure. The growing hydrogen fraction in fuel blends significantly increases the oscillation frequency. In addition, the pulsating detonation frequency rises with increasing equivalence ratio under fuel-lean conditions, peaks under stoichiometric conditions, and falls under fuel-rich conditions as the equivalence ratio increases further. Evolutions of reactants, main intermediate radicals, and products are analysed in both fuel-lean and fuel-rich conditions. A chemical explosive mode analysis further confirms the highly-autoignitive nature of the mixture in the induction zone between reaction front and shock front where thermal diffusion plays a negligible role.

Diffusion of krypton and xenon in uranium mononitride; a Density Functional Theory Study

Uranium mononitride is a strong candidate for an advanced nuclear fuel. In this work we use density functional theory to model the diffusivity of matrix U atoms, as well as the noble gas (Ng) fission products Kr and Xe, at the atomic scale under three stoichiometric conditions (U-rich, stoichiometric, N-rich). U self-diffusion is found to be dependent on stoichiometry, being largest under N-rich conditions. The U formation entropy significantly affects the U self-diffusion coefficient, indicating that it is necessary to consider the vibrational properties of the system to accurately describe diffusion properties in UN. The calculated Kr and Xe diffusion coefficients from the U vacancy (VU)-assisted mechanism are much larger than by interstitial mechanisms under the three stoichiometric conditions studied. The two mechanisms show opposite stoichiometric dependence, with the former increasing from U-rich to N-rich conditions and the latter decreasing. Kr moves significantly more quickly than Xe via the interstitial mechanism due to the larger atomic radius of the latter, while the effect of atomic size on the VU-assisted mechanism is negligible, indicating similar diffusivity of Kr and Xe in UN. The good agreement with experiment of our calculated Xe monovacancy-assisted diffusion coefficient indicates that the monovacancy-assisted mechanism governs the Ng diffusion in UN, and supports the accuracy of our theoretical model.

Exhaust emission characteristics of stoichiometric combustion applying to diesel particulate filter(DPF) and three-way catalytic converter(TWC)

Various researchers study after-treatment system (DPF, SCR, LNT, TWC) to meet the recent strengthening regulation. In this study, we consider the intake air applying to the simulated-EGR which is composed of synthetic constituents (e.g. air, N2, and CO2 gas). Intake air excessively used to simulated-EGR, proceeds with the stoichiometric air-fuel ratio combustion in the cylinder. This stoichiometric exhaust emission was passed through and converted in TWC as well as DPF after-treatment system. We discuss exhaust emission characteristics of stoichiometric combustion applying to DPF and TWC in compression ignition diesel engine. The maximum of the conversion efficiency of NOx is 85.7% at SOI of −18.2° CA. aTDC with simulated-EGR the smoke reduction efficiency of soot is high and is provided over 99% reduction under the stoichiometric condition with reduced O2 mole fraction by adding only N2 and with EGR.

Role of ozone addition on premixed hydrogen/oxygen flames: Multi-zone structure and multi-regime dynamics

This study investigates the effects of additive ozone on the ignition and propagation of premixed hydrogen/oxygen flames, with emphasis on the steady flame structure and the transient ignition and propagation behaviors due to the ozone chemistry and transport. We first simulate the 1D freely-propagating hydrogen/oxygen flames with and without additive ozone, and demonstrate that the ozone-enhanced flame has a triple reaction layer structure, which consists of an ozone reaction layer, with substantial heat release, situated within the entire preheat zone. This spatially non-monotonic nature of the heat release rate and the associated temperature gradient then implies that the conventional definition of the flame thickness, δ=(Tb-Tu)/(dT/dx)max, is incapable and indeed inappropriate to characterize the ozone-enhanced flame thickness. The multi-zone flame structure then leads to multi-regime flame dynamics, with the structure of a single ozone-sustained branch followed by decoupled and coupled double branches controlled by ozone and oxygen reactions respectively. The critical radius and the transition regime of the ozone branch are captured over a wide range of equivalence ratios, which are induced by the large Lewis number of ozone and the interaction between the ozone and oxygen branches. As such, the regime diagram of the flame propagation speed versus the stretch rate respectively corresponds to three to six regimes in the ozone branch, and zero to five regimes in the oxygen branch under ultra-(fuel)-lean, fuel-lean, stoichiometric and fuel-rich conditions. The modification of the minimum ignition energy in ozone–assisted flames is also noted.

Heat release peculiarities of polyoxymethylene dimethyl ether 1 – Part I: Effect of initial thermochemical conditions

Polyoxymethylene dimethyl ethers are strongly discussed as a promising oxygenated substitutes and potentially carbon-neutral fuels for compression-ignition engines. Polyoxymethylene dimethyl ether 1, also known as methylal or dimethoxymethane is the simplest representative of this family. Detailed knowledge of methylal combustion characteristics and underlying chemical kinetics are required to fully assess its combustion potential. In this study a numerical investigation of combustion heat release peculiarities of methylal/oxidizer propellant subjected to spontaneous auto-ignition was conducted in a constant-volume adiabatic reactor. The domain of initial conditions (temperature, pressure, equivalence ratio) promoting a discovered three-stage methylal heat release was outlined and analyzed for the first time. Fourteen detailed methylal kinetic mechanisms were validated against experimental ignition delay data. Three mechanisms (among fourteen) predicting in the most accurate manner the experimental data were selected to simulate the auto-ignition behavior of methylal/air mixtures. The overall range of examined initial in-reactor conditions spanned temperatures of 600–1400 K, pressures of 10–40 bar, and equivalence ratios of 0.1–2.0. The unknown previously three-stage methylal heat release phenomenon was revealed to predominantly occur within low-to-intermediate initial temperature range (below 900 K) at ultra-lean conditions (equivalence ratios below 0.5). The third-stage was found to exhibit prolonged CO2 and H2O formation supposedly due to lessened temperature gain prior to CO-to-CO2 chemistry and competing H2O formation pathways. At stoichiometric and rich conditions, an evidence of the three-stage ignition was found with high proximities between the latter stages. A comparative analysis with the highly-reactive non-oxygenated n-alkane representative, n-heptane, was conducted.

Gold(I) α‐Trifluoromethyl Carbenes: Synthesis, Characterization and Reactivity Studies

AbstractAryl trifluoromethyl diazomethanes 2‐R (R=Ph, OMe, CF3) are readily decomposed by the (o‐carboranyl)diphosphine gold(I) complex 1. The resulting α‐CF3 substituted carbene complexes 3‐R have been characterized by multi‐nuclear NMR spectroscopy as well as X‐ray crystallography (for 3‐Ph). The bonding situation was thoroughly assessed by computational means, showing stabilization of the electrophilic carbene center by π‐donation from the aryl substituent and backdonation from Au, as enhanced by the chelating P^P ligand. Reactivity studies under stoichiometric and catalytic conditions substantiate typical carbene‐type behavior for 3‐Ph.

Gold(I) α-Trifluoromethyl Carbenes: Synthesis, Characterization and Reactivity Studies.

Aryl trifluoromethyl diazomethanes 2‐R (R=Ph, OMe, CF3) are readily decomposed by the (o‐carboranyl)diphosphine gold(I) complex 1. The resulting α‐CF3 substituted carbene complexes 3‐R have been characterized by multi‐nuclear NMR spectroscopy as well as X‐ray crystallography (for 3‐Ph). The bonding situation was thoroughly assessed by computational means, showing stabilization of the electrophilic carbene center by π‐donation from the aryl substituent and backdonation from Au, as enhanced by the chelating P^P ligand. Reactivity studies under stoichiometric and catalytic conditions substantiate typical carbene‐type behavior for 3‐Ph.