Synthesis and catalytic application of a donor-free bismuthenium cation

Herein, we report the synthesis and catalytic application of a new N,N'-dineopentyl-1,2-phenylenediamine-based bismuthenium cation (3). 3 has been synthesized via the treatment of chlorobismuthane LBiCl [L = 1,2-C6H4{N(CH2tBu)}2] (2) with AgSbF6, and was further used as a robust catalyst for the cyanosilylation of ketones under mild reaction conditions. Experimental studies and DFT calculations were performed to understand the mechanistic pathway.

Applications of low-valent compounds with heavy group-14 elements

Over the last two decades, the low-valent compounds of group-14 elements have received significant attention in several fields of chemistry owing to their unique electronic properties. The low-valent group-14 species include tetrylenes, tetryliumylidene, tetrylones, dimetallenes and dimetallynes. These low-valent group-14 species have shown applications in various areas such as organic transformations (hydroboration, cyanosilylation, N-functionalisation of amines, and hydroamination), small molecule activation (e.g. P4, As4, CO2, CO, H2, alkene, and alkyne) and materials. This review presents an in-depth discussion on low-valent group-14 species-catalyzed reactions, including polymerization of rac-lactide, L-lactide, DL-lactide, and caprolactone, followed by their photophysical properties (phosphorescence and fluorescence), thin film deposition (atomic layer deposition and vapor phase deposition), and medicinal applications. This review concisely summarizes current developments of low-valent heavier group-14 compounds, covering synthetic methodologies, structural aspects, and their applications in various fields of chemistry. Finally, their opportunities and challenges are examined and emphasized.

Stepwise and Controllable Synthesis of Mesoporous Heterotrimetallic Catalysts Based on Predesigned Al4 Ln4 Metallocycles

The motivation for making heterometallic compounds stemmed from their emergent synergistic properties and enhanced capabilities for applications. However, the atomically precisely controlled synthesis of heterometallic compounds remains a daunting challenge of the complications that arise when applying several metals and linkers. Herein, a stepwise and controlled method is reported for the accurate addition of second and third metals to homometallic aluminum macrocycles based on the synergistic coordination and hard-soft acid-base theory. These heterometallic compounds showed a good Lewis acid catalytic effect, and the addition of hetero-metals significantly improved the catalytic effect and rate, among that the conversion rate of compound AlOC-133 reached 99.9% within half an hour. This method combines both the independent controllability of stepwise assembly with the universality of one-step methods. Based on the large family of clusters, the establishment of this method paves the way for the controllable and customized molecular-level synthesis of heterometallic materials and creates materials customized for preferential application.

Accurate binding of porous aluminum molecular ring catalysts with the substrate

Metal molecular rings are a class of compounds with aesthetically pleasing symmetry and fundamentally useful properties. The reported work generally focuses on the ring center cavity, and there is little known about those on the ring waist. Herein, we report the discovery of porous aluminum molecular rings and their performance and contribution to the cyanosilylation reaction. We develop a facile ligand induced aggregation and solvent regulation strategy towards AlOC-58NC and AlOC-59NT with high purity, high yield (75% and 70%, respectively) and gram-level scale-up. These molecular rings exhibit a "two-tier" pore feature involving the general central cavity and newly observed equatorial semi-open cavities. AlOC-59NT with two types of one-dimensional channels showed good catalytic activity. The interaction of the aluminum molecular ring catalyst with the substrate has been crystallographically characterized and theoretically confirmed, showing a ring adaptability process that involves the capture and binding of the substrate. This work provides new ideas for the assembly of porous metal molecular rings and to understand the overall reaction pathway involving aldehydes and is expected to inspire the design of low-cost catalysts through structural modifications.

A Sacrificial Iminato Ligand in the Catalytic Cyanosilylation of Ketones Promoted by Organoactinide Complexes

Four new complexes containing the bis(pentamethylcyclopentadienyl)thorium(IV) moiety, Cp*₂Th(L1)(Me) (Th2), Cp*₂Th(L2)(Me) (Th3), Cp*₂Th(L1)Cl (Th5), and Cp*₂Th(L2)Cl (Th6), were synthesized in quantitative yields via the protonolysis reaction of the metallocene precursor complexes Cp*₂Th(Me)₂ (Th1) and Cp*₂Th(Me)Cl (Th4) and the respective six- and seven-membered N-heterocyclic neutral imine ligands L1H and L2H. The molecular structures of all the complexes were established by single-crystal X-ray structure analyses. The synthesized complexes along with the precursor complexes were employed as catalysts for the cyanosilylation reaction of ketones with trimethylsilyl cyanide (Me₃SiCN). The removal of the iminato ligand is necessary to trigger the reaction, allowing the formation of the active catalyst.

Stannylene cyanide and its use as a cyanosilylation catalyst

The usefulness of stannylene cyanide (ATISnCN (5); ATI = aminotroponiminate) as a catalyst for the cyanosilylation of aldehydes is demonstrated.

Reduction of tert-butylphosphaalkyne and trimethylsilylnitrile with magnesium(I) dimers

We report on the reactivity of magnesium(I) dimers, [Mg(nacnac)]₂ (nacnac = HC[C(Me)N(2,6-ⁱPr₂C₆H₃)]₂ ([^DippLMg]₂) and HC[C(Me)N(2,4,6-Me₃C₆H₂)]₂ ([^MesLMg]₂)), towards the phosphaalkyne ^tBuCP. The steric profile of the magnesium(I) dimer results in selectivity for different products. The larger diisopropylphenyl derivative yields exclusively the monomeric dimagnesiated phosphaalkene [^DippLMg]PC(^tBu)([^DippLMg]) (1), while the mesityl derivative facilitates reductive coupling of two phosphaalkyne equivalents to give access to the 1,3-diphosphacyclobutadienediide [^MesLMg]₂[(^tBu)₂C₂P₂](2). The reactivity differs in coordinating solvents such as THF, which allowed for the observation of C-P coupled products. For sake of comparison, reactions of magnesium(I) compounds with Me₃SiCN were carried out. In contrast to the reactions involving ^tBuCP, these afforded 1,3-diazabutadienediyl complexes via reductive coupling and silyl migration processes.

n-Butyllithium as a highly efficient precatalyst for cyanosilylation of aldehydes and ketones

A highly efficient cyanosilylation protocol mediated by the easily available n-BuLi with a wide range of aldehydes and ketones was developed. This protocol features excellent yields with very low n-BuLi loadings (0.01-0.05 mol%) at room temperature, solvent-free process, good chemo-/regio-selectivity and functional group tolerance and scalability. A possible reaction pathway based upon stoichiometric reactivity was put forward.

Application of an Electrochemical Microflow Reactor for Cyanosilylation: Machine Learning-Assisted Exploration of Suitable Reaction Conditions for Semi-Large-Scale Synthesis

Cyanosilylation of carbonyl compounds provides protected cyanohydrins, which can be converted into many kinds of compounds such as amino alcohols, amides, esters, and carboxylic acids. In particular, the use of trimethylsilyl cyanide as the sole carbon source can avoid the need for more toxic inorganic cyanides. In this paper, we describe an electrochemically initiated cyanosilylation of carbonyl compounds and its application to a microflow reactor. Furthermore, to identify suitable reaction conditions, which reflect considerations beyond simply a high yield, we demonstrate machine learning-assisted optimization. Machine learning can be used to adjust the current and flow rate at the same time and identify the conditions needed to achieve the best productivity.

Germyliumylidene: A Versatile Low Valent Group 14 Catalyst

Bis‐NHC stabilized germyliumylidenes [RGe(NHC)₂]⁺ are typically Lewis basic (LB) in nature, owing to their lone pair and coordination of two NHCs to the vacant p‐orbitals of the germanium center. However, they can also show Lewis acidity (LA) via Ge−C^NHC σ* orbital. Utilizing this unique electronic feature, we report the first example of bis‐NHC‐stabilized germyliumylidene [^MesTerGe(NHC)₂]Cl (1), (^MesTer=2,6‐(2,4,6‐Me₃C₆H₂)₂C₆H₃; NHC= IMe₄=1,3,4,5‐tetramethylimidazol‐2‐ylidene) catalyzed reduction of CO₂ with amines and arylsilane, which proceeds via its Lewis basic nature. In contrast, the Lewis acid nature of 1 is utilized in the catalyzed hydroboration and cyanosilylation of carbonyls, thus highlighting the versatile ambiphilic nature of bis‐NHC stabilized germyliumylidenes.

An uncoordinated tertiary nitrogen based tricarboxylate calcium network with Lewis acid-base dual catalytic sites for cyanosilylation of aldehydes

The design and utilization of dual sites for synergistic catalysts has been recognised as an efficient method towards high-efficiency catalysis in the cyanosilylation of aldehydes, which gives key intermediates for the synthesis of a number of valuable natural and pharmaceutical compounds. However, most of the reported dual-site catalysts for this reaction were homogeneous, accompanied by potential deactivation through internal complexation of the dual sites. Herein, by the rational selection of an uncoordinated tertiary nitrogen based tricarboxylic ligand (tris[(4-carboxyl)-phenylduryl]amine, H3TCBPA), a new three-dimensional calcium-based metal-organic framework (MOF), Ca3(TCBPA)2(DMA)2(H2O)2 (1, where TCBPA = ionized tris[(4-carboxyl)-phenylduryl]amine and DMA = N,N-dimethylacetamide), possessing accessible dual catalytic sites, Lewis-basic N and Lewis-acidic Ca, has been designed and constructed by a one-pot solvothermal reaction. As expected, 1 is capable of dually and heterogeneously catalysing the cyanosilylation of aldehydes at room temperature, and can be reused for at least 6 runs with a maximum turnover number (TON) of 1301, which is superior to most reported cases. Additionally, 1 shows CO2 adsorption ability and conversion with epoxides, which is beneficial for the establishment of a sustainable society.

Cyanosilylation by Compounds with Main-Group Elements: An Odyssey

The past few decades have seen remarkable headways in the structural and reaction chemistry of compounds with heavier main-group elements. In recent years, there is an ongoing effort to derive catalytic chemistry involving main-group compounds, driven by their lower costs and higher terrestrial abundances. Here, a survey on the state-of-the-art in the development of cyanosilylation methodology by compounds with heavier main-group elements has been given. Once dominated by transition metals, the field has matured to embrace the majority of the main-group elements including aluminum, silicon, and calcium. Of particular focus will be how the mechanism of cyanosilylation involving compounds with main-group elements differs from those of transition metals.

The direct trifluoromethylsilylation and cyanosilylation of aldehydes via an electrochemically induced intramolecular pathway

The trifluoromethylsilylation and cyanosilylation of aldehydes via the intramolecular cleavage of Si–CN and Si–CF₃ bonds are developed based on electrochemically induced Si–O affinity.

Easily accessible lithium compound catalyzed mild and facile hydroboration and cyanosilylation of aldehydes and ketones

Simple and readily accessible lithium compounds are found to be efficient single site catalysts for cyanosilylation and hydroboration of a range of aldehydes and ketones under ambient conditions.

Low-valent magnesium(i)-catalyzed cyanosilylation of ketones

The magnesium(i) complex [(^XylNacnac)Mg]₂ was employed as a highly efficient catalyst for ketone cyanosilylation with TMSCN under mild conditions.