Unsaturated Atoms Research Articles

Practical H2 supply from ammonia borane enabled by amorphous iron domain

Efficient catalysis of ammonia borane (AB) holds potential for realizing controlled energy release from hydrogen fuel and addressing cost challenges faced by hydrogen storage. Here, we report that amorphous domains on metallic Fe crystal structures (R-Fe2O3 Foam) can achieve AB catalytic performances and stability (turnover frequency (TOF) of 113.6 min−1, about 771 L H2 in 900 h, and 43.27 mL/(min·cm2) for 10×10 cm2 of Foam) that outperform reported benchmarks (most <14 L H2 in 45 h) by at least 20 times. These notable increases are enabled by the stable Fe crystal structure, while defects and unsaturated atoms in the amorphous domains form Fe-B intermediates that significantly lower the dissociation barriers of H2O and AB. Given that the catalyst lifetime is a key determinant for the practical use in fuel cells, our R-Fe2O3 Foam also provides decent H2 supply (180 mL H2/min, AB water solution of 7.5 wt% H2) in a driven commercial car fuel cell at stable power outputs (7.8 V and 1.6 A for at least 5 h). When considered with its facile synthesis method, these materials are potentially very promising for realizing durable high-performance AB catalysts and viable chemical storage in hydrogen powered vehicles.

Shape controlled synthesis and crystal facet dependent gas sensitivity of tungsten oxide

Gas sensors can achieve remarkable functionality through the optimization of particle size, shapes, crystal facets, and oxygen defects, resulting in unsaturated coordination atoms, high charge densities, and enhanced bond energies. In this study, WO2.72 nanourchins, WO3-x nanowires, and WO3 nanorods/nanocube with (010), (001), (200), and (002) dominant crystal facets were synthesized and used as gas sensing materials. It was found that WO2.72 nanourchins exhibit an excellent response of Ra/Rg=21 to 100 ppm acetone with good selectivity among other sensors as-fabricated. First-principle calculations of Density Functional Theory were performed on acetone's adsorption on different crystal planes of tungsten oxide. The results verify spontaneous and fast adsorption on the (010) crystal plane than on the (001) and (200) planes. Further characterizations indicate that WO2.72 nanourchins with (010) crystal facets contain more reactive sites with high surface energy, facilitating charge separation, increasing charge carrier mobility, and enabling the redox reactions to occur independently at different rates. Moreover, their richer electron-donor surface oxygen defects, smaller feature sizes, and higher surface area (SBET) with hierarchical porous structures, all contribute to the enhanced acetone sensing. Our work provides a strategy for improved acetone sensing based on optimizing the particle shape with different crystal facets and oxygen vacancy density. We further expect our strategy to be applicable in designing other sensor materials with efficient charge separation and fast surface redox reactions to detect toxic gases.

Insight into the polysulfides conversion kinetics and its activation energy relationship on ultrafine V8C7 in Li-S batteries

Catalytic conversion of lithium polysulfides (LiPSs) is regarded as an effective approach to boosting kinetics and suppressing shuttling effect in lithium-sulfur (Li-S) batteries, but developing efficient catalysts and understanding of its catalytic mechanism still remain challenges. Herein, the ultrafine V8C7 nanocrystals embedded into the porous N-doped carbon frameworks (V8C7/NC) was designed for accelerating the LiPSs catalytic-conversion kinetics toward high-performance Li-S batteries. We propose that the ultrafine V8C7 nanocrystals with abundant unsaturated coordination atoms increase the active sites for catalytic-conversion of LiPSs and also accelerate the corresponding kinetics by reducing its reaction activation energy, meanwhile the interlinked nano-channels of V8C7/NC can effectively confine LiPSs and also promote electron/ion transfer. These attributes enable the Li-S cell equipped with V8C7/NC to deliver a large discharge capacity of 1393.3 mAh g−1 at 0.2 C, excellent rate capability (496.0 mAh g−1 at 10 C), and robust cycling stability (1000 cycles with a negligible capacity decay rate of 0.019 % per cycle even at 5 C). The innovative concept of ultrafine V8C7 nanocrystals embedded into the porous carbon toward improved LiPSs catalytic-conversion kinetics could be extended to develop other electrocatalytic hosts for high-performance Li-S batteries.

Thermal stability of MDM and oxidative decomposition mechanism under the condition of air infiltration: A combined experimental, ReaxFF-MD and DFT study

When siloxanes are used as the working fluids of organic Rankine cycle systems, there is a possibility of air infiltration due to the large vacuum present in the condenser. To address this issue, experimental and simulation studies were conducted on the thermal stability and pyrolysis product characteristics of octamethyltrisiloxane (MDM) in the presence of air. The results indicated that air significantly promotes the decomposition of MDM at the temperatures above 250 °C. Air was helpful in increasing the formation of CH2O, CO, and CO2, and also enhanced polymerization of decomposition product of siloxane, leading to higher yields of MD2M, MD3M, MD4M, D3, D4, and D5. By combining reactive force field molecular dynamics (ReaxFF-MD) simulations with density functional theory (DFT) calculations, the microscopic mechanisms of MDM's oxidative decomposition by O2 in air and H2O under humid conditions were elucidated. O2 can easily combine with unsaturated Si atoms to form Si-O bonds, combine with CH3 radicals to form C-O bonds, and undergoes hydrogen extraction reactions to initiate decomposition. H2O mainly undergoes initial decomposition through CH3 radical hydrogenation and binding with unsaturated Si atoms. The generated O2H, O, and OH radicals tend to bind with Si atoms in molecules and radicals, facilitating polymerization reactions.

Constructing Unsaturated Ru Atom Arrays Confined in Mn Oxides to Boost Neutral Water Reduction

Recently, Ru single atoms supported on carbon nanomaterials have demonstrated ultrahigh activity for acid hydrogen evolution reaction (HER), however their neutral HER activity remains low due to the sluggish kinetics for both the water dissociation step to generate H* intermediates and subsequent H* recombination in neutral electrolytes. Here, we synthesize ordered low‐coordinated Ru atom arrays confined in Mn oxides (i.e., Li4Mn5O12) for concurrently boosting the water dissociation and H* recombination, thus achieving a 6‐fold HER activity enhancement than commercial Pt/C in neutral media. Control experiments indicate that low‐coordinated Ru atoms with strong affinity to oxygen atoms of water molecules facilitate the water dissociation to rapidly generate H*. More importantly, both electrochemical and theoretic results uncover that the array‐like structure allows the activation of two water molecules on two adjacent Ru atoms for enabling direct H*–H* recombination via the Tafel step, while isolated Ru atoms can only activate water one by one for recombining H* via the sluggish Heyrovsky step. Clearly, this work paves new avenues to boosting the electrocatalytic activity by constructing ordered metal atoms assembles with controllable coordination environments.

Supported Au single atoms and nanoparticles on MoS2 for highly selective CO2-to-CH3COOH photoreduction

Effectively controlling the selective conversion of CO2 photoreduction to C2 products presents a significant challenge. Here, we develop a heterojunction photocatalyst by controllably implanting Au nanoparticles and single atoms into unsaturated Mo atoms of edge-rich MoS2, denoted as Aun/Au1-CMS. Photoreduction of CO2 results in the production of CH3COOH with a selectivity of 86.4%, which represents a 6.4-fold increase compared to samples lacking single atoms, and the overall selectivity for C2 products is 95.1%. Furthermore, the yield of CH3COOH is 22.4 times higher compared to samples containing single atoms and without nanoparticles. Optical experiments demonstrate that the single atoms domains can effectively capture photoexcited electrons by the Au nanoparticles, or the local electric field generated by the nanoparticles promotes the transfer of photogenerated electrons in MoS2 to Au single atoms, prolonging the relaxation time of photogenerated electrons. Mechanistic investigations reveal that the orbital coupling of Au5d and Mo4d strengthens the oxygen affinity of Mo and carbon affinity of Au. The hybridized orbitals reduce energy splitting levels of CO molecular orbitals, aiding C–C coupling. Moreover, the Mo−Au dual-site stabilize the crucial oxygen-associated intermediate *CH2CO, thereby enhancing the selectivity towards CH3COOH. The cross-scale heterojunctions provide an effective strategy to simultaneously address the kinetical and thermodynamical limitations of CO2-to-CH3COOH conversion.

Enhancing electrocatalytic nitrate/nitric oxide reduction to NH3 on two-dimensional p-block InSe monolayer via defect engineering

Electrochemical nitrate/nitric oxide (NO3−/NO) reduction to ammonia (NH3) is an environmentally friendly and sustainable strategy that mitigates pollutants while synthesizing value-added products NH3. Despite the prevalence of transition metal-based catalysts, the exploration of inexpensive two-dimensional (2D) p-block materials is needed in NH3 synthesis. Based on density functional theory calculations, we proposed an InSe monolayer with single Se vacancy as an outstanding catalyst for NO3RR and NORR. The catalyst exhibits exceptional catalytic performance, characterized by a low limiting potential comparable to that of most transition metal-based catalysts, and efficaciously suppresses the formation of competitive by-products. Successful adsorption and activation of NO3− and NO molecules are achieved, attributed to the charge rearrangement around the vacancy. The electronic structure analysis reveals that the enhancement of activity stems from the upward shift of the p-band center of unsaturated indium atoms. This work heralds a novel avenue for designing pure 2D p-block NH3 synthesis catalysts and sheds light on a deeper understanding of the catalytic mechanism at the electronic level.

Silicate minerals enable the efficient photocatalytic RWGS reaction

Silicate minerals are the most abundant minerals on Earth’s crust and can originate from rock-forming minerals with the low risk to the environment. Herein, the chain pyroxene mineral NaFeSi2O6 nanosheets loaded with highly dispersed Cu nanoparticles have been used as an archetype platform for the efficient photocatalytic reverse water gas shift (RWGS) reaction. The resultant Cu/NaFeSi2O6 catalyst demonstrated high performance metrics in the gas-phase photocatalytic hydrogenation of CO2 to CO, with a yield as high as 13144 μmol gcat–1 h–1. It is shown that the coordinately unsaturated Fe atom in NaFeSi2O6 can serve as a robust Lewis acid site for adsorbing and activating CO2 molecules, while the metal/support interface facilitates the formation of intermediate species and the subsequent production of CO products through hydrogen spillover. The surface plasmon resonance (SPR) effect of Cu further promotes the injection of hot electrons into NaFeSi2O6 and the carrier separation and migration at the Schottky heterojunction. This low-cost and earth-abundant mineral-based catalyst exhibits 100 h of long-term photocatalytic stability, indicating its potential as a promising and feasible candidate for the future development of renewable synthetic fuels.

Copper Deposited on Reduced Titania as Catalyst for the Production of CH4 from Sunlight and Air

AbstractAtmospheric CO2 and H2O adsorbed on the photocatalyst surface undergo sunlight‐assisted conversion to solar products that bridge the gaps between artificial and natural photosynthesis. Herein, we report a Lewis acid‐base interaction derived photocatalyst, Cu deposited on reduced titania, that harvests CO2 and H2O from the air and transforms them to CH4. Photocatalyst surface studies confirm that coordinately unsaturated Cu atoms and oxygen vacancies are formed that facilitate CO2 and H2O adsorption. The mechanistic studies, combined with tandem secondary ion mass spectroscopy and isotopic labelling, confirm the CH4 origin from atmosphere‐adsorbed CO2 and H2O. The contributing factors to photocatalyst instability are explored. We expect that this study will have an impact on the widespread application and economic viability of photocatalytic CO2 reduction.

Ultra-Large Two-Dimensional Metal Nanowire Networks by Microfluidic Laminar Flow Synthesis for Formic Acid Electrooxidation.

Despite the great research interest in two-dimensional metal nanowire networks (2D MNWNs) due to their large specific surface area and abundance of unsaturated coordination atoms, their controllable synthesis still remains a significant challenge. Herein, a microfluidics laminar flow-based approach is developed, enabling the facile preparation of large-scale 2D structures with diverse alloy compositions, such as PtBi, AuBi, PdBi, PtPdBi, and PtAuCu alloys. Remarkably, these 2D MNWNs can reach sizes up to submillimeter scale (~220 μm), which is significantly larger than the evolution from the 1D or 3D counterparts that typically measure only tens of nanometers. The PdBi 2D MNWNs affords the highest specific activity for formic acid (2669.1 mA mg-1) among current unsupported catalysts, which is 103.5 times higher than Pt-black, respectively. Furthermore, in situ Fourier transform infrared (FTIR) experiments provide comprehensive evidence that PdBi 2D MNWNs catalysts can effectively prevent CO* poisoning, resulting in exceptional activity and stability for the oxidation of formic acid.

Ultra‐Large Two‐Dimensional Metal Nanowire Networks by Microfluidic Laminar Flow Synthesis for Formic Acid Electrooxidation

AbstractDespite the great research interest in two‐dimensional metal nanowire networks (2D MNWNs) due to their large specific surface area and abundance of unsaturated coordination atoms, their controllable synthesis still remains a significant challenge. Herein, a microfluidics laminar flow‐based approach is developed, enabling the facile preparation of large‐scale 2D structures with diverse alloy compositions, such as PtBi, AuBi, PdBi, PtPdBi, and PtAuCu alloys. Remarkably, these 2D MNWNs can reach sizes up to submillimeter scale (~220 μm), which is significantly larger than the evolution from the 1D or 3D counterparts that typically measure only tens of nanometers. The PdBi 2D MNWNs affords the highest specific activity for formic acid (2669.1 mA mg−1) among current unsupported catalysts, which is 103.5 times higher than Pt‐black, respectively. Furthermore, in situ Fourier transform infrared (FTIR) experiments provide comprehensive evidence that PdBi 2D MNWNs catalysts can effectively prevent CO* poisoning, resulting in exceptional activity and stability for the oxidation of formic acid.

Reaction dynamics simulation of MoO2 cluster precursor with melting, deoxygenation and sulfuration for MoS2 growth by chemical vapor deposition

Chemical vapor deposition (CVD) is a promising strategy for achieving fascinating large-scale production of MoS2. During CVD, MoO2 exhibits high reactivity and can effectively inhibit intermediate phase formation. Although, the experiments qualitatively demonstrate the MoO2 sulfuration mechanism, the reaction dynamics process on the atomic level is not clear. Herein, according to our previous experimental results of pre-deposited MoO2 vapor–liquid-solid growth MoS2, we investigate microscopic reaction events, including melting, deoxygenation, and sulfuration by reactive molecular dynamics simulation as follow: Terminal oxygen in pre-melting zone on the cluster surface has high reactivity, leading to deoxygenation occurring during melting. The unsaturated coordination Mo atoms are more accessible to sulfuration. With a long simulation time, MoO2 is transformed into MoO0.27S1.95 in which MoS2-like clusters account for up to 92.45 % after annealing. We hope that our work will provide theoretical support for the controlled CVD synthesis of MoS2 and other transition metal dichalcogenides.

Plasma induced grain boundaries to boost electrochemical reduction of CO2 to formate

Bismuth-based catalysts are highly promising for the electrochemical carbon dioxide reduction reaction (eCO2RR) to formate product. However, achieving high activity and selectivity towards formate and ensuring long-term stability remains challenging. This work reports the oxygen plasma inducing strategy to construct the abundant grain boundaries of Bi/BiOx on ultrathin two-dimensional Bi nanosheets. The oxygen plasma-treated Bi nanosheet (OP-Bi) exhibits over 90% Faradaic efficiency (FE) for formate at a wide potential range from −0.5 to −1.1 V, and maintains a great stability catalytic performance without significant decay over 30 h in flow cell. Moreover, membrane electrode assembly (MEA) device with OP-Bi as catalyst sustains the robust current density of 100 mA cm−2 over 50 h, maintaining a formate FE above 90%. In addition, rechargeable Zn-CO2 battery presents the peak power density of 1.22 mW cm−2 with OP-Bi as bifunctional catalyst. The mechanism experiments demonstrate that the high-density grain boundaries of OP-Bi provide more exposed active sites, faster electron transfer capacity, and the stronger intrinsic activity of Bi atoms. In situ spectroscopy and theoretical calculations further elucidate that the unsaturated Bi coordination atoms between the grain boundaries can effectively activate CO2 molecules through elongating the C–O bond, and reducing the formation energy barrier of the key intermediate (*OCOH), thereby enhancing the catalytic performance of eCO2RR to formate product.

Enhanced sensing properties of CoFe2O4 nanosheet and sensing reaction molecule mechanism of polar CoFe2O4 {111} surfaces

The sensitivity of nanostructures to gases can be improved by exposing their polar surfaces. In this project, a CoFe2O4 nanosheet with {111} polar surface was obtained by selective adsorption of -OH, -OHC2H5OH, and SO42-. By hydrogenating the polar surface of Fe-CoFe2O4 (111), the -OH, -OC2H5OH and SO42- groups were effectively removed, which greatly improved the gas sensing sensitivity of CoFe2O4 nanosheets. This innovative technique provides a feasible way to improve the gas sensing performance of nanosheets. The results show a significant increase in the number of coordination-unsaturated metal-iron atoms (Fe3c) on polar surfaces, which improves sensitivity. As a gas sensing centre, Fe3c can adsorb oxygen, generate free electrons and catalyse sensing reactions. A microscopic mechanism for gas sensing is thus proposed. These results suggest that coordinated unsaturated metal atoms on the surface of metal oxides are active sites for gas sensing and that this gas sensing mechanism is universal.

Molecular Geometry Impact on Deep Learning Predictions of Inverted Singlet-Triplet Gaps.

We present a deep learning model able to predict excited singlet-triplet gaps with a mean absolute error (MAE) of ≈20 meV to obtain potential inverted singlet-triplet (IST) candidates. We exploit cutting-edge spherical message passing graph neural networks designed specifically for generating 3D graph representations in molecular learning. In a nutshell, the model takes as input a list of unsaturated heavy atom Cartesian coordinates and atomic numbers, producing singlet-triplet gaps as output. We exploited available large data collections to train the model on ≈40,000 heterogeneous density functional theory (DFT) geometries with available ADC(2)/cc-pVDZ singlet-triplet gaps. We ascertain the predictive power of the model from a quantitative perspective obtaining predictions on a test set of ≈14,000 molecules, whose geometries have been generated at DFT level (the same employed for the geometries in the training set), at GFN2-xTB level, and through Molecular Mechanics. We notice performance degradation upon switching to lower-quality geometries, with GFN2-xTB ones maintaining satisfactory results (MAE ≈ 50 meV on GFN2-xTB geometries, MAE ≈ 180 meV on generalized AMBER force field geometries), hinting at caution when dealing with specific chemical classes. Finally, we verify the performance of the model from the qualitative point of view, obtaining predictions on a different data set of ≈15,000 molecules already used to identify new IST molecules. We obtained predictions using both DFT and experimental X-ray geometries, with results on IST candidates similar to those provided by quantum chemical methods, with clear hints for the path toward improved performance.

Microwave-Assisted Hydrothermal Synthesis of {100} and {111} Faceted LiFeO2 Truncated Octahedra: Investigations on Volatile Organic Compound Sensing Performance.

Growth of exposed crystal facets has received considerable attention because of their coordinatively unsaturated surface atoms and defect-related surface reactivities. Herein, LiFeO2 truncated octahedra exposed with 6 {100} facets and 8 {111} facets were prepared through a simple microwave-assisted hydrothermal method without using any additives, surfactants, and calcination processes. The detailed growth process revealed that the formation of LiFeO2 truncated octahedra occurred only at the optimized reaction temperature (180 °C), time (30 min), and reactant concentrations. The prepared LiFeO2 truncated octahedra showed excellent sensing responses toward aliphatic organic compounds compared to that against aromatic organic compounds and poor response to inorganic compounds. The response percentages of 150 ppm concentrations of acetone, ethanol, formaldehyde, and isopropyl alcohol are 81.84, 62.91, 62.68, and 69.41%, respectively, at a low operating temperature (100 °C). The presence of exposed facets with their coordinatively unsaturated Li/Fe surface atoms such as 5-fold {100}, 3-fold {111}, 3-fold {100}-{111}, 2-fold {111}-{111}, and 2-fold coordination with the O atom in the vertices facilitated more oxygen vacancies and led to improved surface reactivities as well as sensitivity.

High-spin Co3+ in cobalt oxyhydroxide for efficient water oxidation

Cobalt oxyhydroxide (CoOOH) is a promising catalytic material for oxygen evolution reaction (OER). In the traditional CoOOH structure, Co3+ exhibits a low-spin state configuration (t2g6eg0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${t}_{2{{{{{\\rm{g}}}}}}}^{6}{e}_{{{{{{\\rm{g}}}}}}}^{0}$$\\end{document}), with electron transfer occurring in face-to-face t2g*\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${t}_{2{{{{{\\rm{g}}}}}}}^{*}$$\\end{document} orbitals. In this work, we report the successful synthesis of high-spin state Co3+ CoOOH structure, by introducing coordinatively unsaturated Co atoms. As compared to the low-spin state CoOOH, electron transfer in the high-spin state CoOOH occurs in apex-to-apex eg*\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${e}_{{{{{{\\rm{g}}}}}}}^{*}$$\\end{document} orbitals, which exhibits faster electron transfer ability. As a result, the high-spin state CoOOH performs superior OER activity with an overpotential of 226 mV at 10 mA cm−2, which is 148 mV lower than that of the low-spin state CoOOH. This work emphasizes the effect of the spin state of Co3+ on OER activity of CoOOH based electrocatalysts for water splitting, and thus provides a new strategy for designing highly efficient electrocatalysts.

Unveiling the Dual Role of Humidity: The Interplay with Defects Manipulating the Charge Carrier Lifetime in Metal Halide Perovskites.

Humidity has exhibited experimentally either beneficial or detrimental effects on the charge carrier lifetime of CH3NH3PbI3 perovskites, leaving the mechanism unresolved. By using ab initio nonadiabatic molecular dynamics simulations, we unveil the dual role of humidity stemming from the complex interplay between water and defects. Beneficially, water passivates iodine vacancies (VI) or grain boundaries (GBs), mitigating electron trapping by reducing nonadiabatic coupling and delaying charge recombination. However, when VI and GBs coexist, water molecules make the two unsaturated lead atoms approach closer and exacerbate electron trapping by deepening the Pb-dimer electron trap that was created by the VI defect, shortening the carrier lifetime to half of pristine CH3NH3PbI3. The study uncovers the origin of the positive and negative effects of humidity on the charge carrier lifetime of perovskites and offers strategies for improving perovskite devices, particularly by avoiding simultaneous point defects and GBs.

Stabilization of NH- Group Adjacent to Naked Silicon(II) Atom in Base Stabilized Aminosilylenes.

Aminosilylene, comprising reactive NH- and Si(II) sites next to each other, is an intriguing class of compounds due to its ability to show diverse reactivity. However, stabilizing the reactive NH- group next to the free Si(II) atom is challenging and has not yet been achieved. Herein, we report the first examples of base stabilized free aminosilylenes Ar*NHSi(PhC(Nt Bu)2 ) (1 a) and Mes*NHSi(PhC(Nt Bu)2 ) (1 b) (Ar*=2,6-dibenzhydryl-4-methylphenyl and Mes*=2,4,6-tri-tert-butylphenyl), tolerating a NH- group next to the naked Si(II) atom. Remarkably, 1 a and 1 b exhibited interesting differences in their reactivity upon heating. With 1 a, an intramolecular C(sp3 )-H activation of one of the benzhydryl methine hydrogen atoms to the Si(II) atom produced the five-membered cyclic silazane 2. However, with 1 b, a rare 1,2-hydrogen shift to the Si(II) atom afforded a silanimine 3, with a hydride ligand attached to an unsaturated silicon atom. Further, the coordination capabilities of 1 a were also tested with Ru(II) and Fe(0) precursors. Treatments of 1 a with [Ru(η6 -p-cymene)Cl2 ]2 led to the isolation of a η6 -arene tethered complex [RuCl2 {Ar*NHSi(PhC(t BuN)2 )-κ1 -Si-η6 -arene}] (4), whereas with the Fe(CO)5 precursor a Fe(0) complex [Fe(CO)4 {Ar*NHSi(PhC(t BuN)2 )-κ1 -Si}] (5) was obtained. Density functional theory (DFT) calculations were conducted to shed light on the structural, bonding, and energetic aspects in 1-5.

Stabilization of NH− Group Adjacent to Naked Silicon(II) Atom in Base Stabilized Aminosilylenes

AbstractAminosilylene, comprising reactive NH− and Si(II) sites next to each other, is an intriguing class of compounds due to its ability to show diverse reactivity. However, stabilizing the reactive NH− group next to the free Si(II) atom is challenging and has not yet been achieved. Herein, we report the first examples of base stabilized free aminosilylenes Ar*NHSi(PhC(NtBu)2) (1 a) and Mes*NHSi(PhC(NtBu)2) (1 b) (Ar*=2,6‐dibenzhydryl‐4‐methylphenyl and Mes*=2,4,6‐tri‐tert‐butylphenyl), tolerating a NH− group next to the naked Si(II) atom. Remarkably, 1 a and 1 b exhibited interesting differences in their reactivity upon heating. With 1 a, an intramolecular C(sp3)−H activation of one of the benzhydryl methine hydrogen atoms to the Si(II) atom produced the five‐membered cyclic silazane 2. However, with 1 b, a rare 1,2‐hydrogen shift to the Si(II) atom afforded a silanimine 3, with a hydride ligand attached to an unsaturated silicon atom. Further, the coordination capabilities of 1 a were also tested with Ru(II) and Fe(0) precursors. Treatments of 1 a with [Ru(η6‐p‐cymene)Cl2]2 led to the isolation of a η6‐arene tethered complex [RuCl2{Ar*NHSi(PhC(tBuN)2)‐κ1‐Si‐η6‐arene}] (4), whereas with the Fe(CO)5 precursor a Fe(0) complex [Fe(CO)4{Ar*NHSi(PhC(tBuN)2)‐κ1‐Si}] (5) was obtained. Density functional theory (DFT) calculations were conducted to shed light on the structural, bonding, and energetic aspects in 1–5.