Single-crystal X-ray Structure Analysis Research Articles

Pd(II)-Catalyzed Directing-Group-Aided C–H Arylation, Alkylation, Benzylation, and Methoxylation of Carbazole-3-carboxamides toward C2,C3,C4-Functionalized Carbazoles

AbstractWe report the Pd(II)-catalyzed β-C–H arylation, alkylation, benzylation, and methoxylation of carbazole-3-carboxamide and carbazole-2-carboxamide substrates, assisted by the bidentate directing groups 8-aminoquinoline or 2-(methylthio)aniline, and construction of C2,C3,C4-functionalized carbazole motifs. The Pd(II)-catalyzed β-C–H arylation reaction was attempted using different directing groups such as 8-aminoquinoline, 2-(methylthio)aniline, 4-amino-2,1,3-benzothiadiazole, 4-methoxyquinolin-8-amine, and butan-1-amine. Through optimization of the reactions, 8-aminoquinoline and 2-(methylthio)aniline were found to be suitable directing groups and, especially, 2-(methylthio)aniline was found to be an efficient directing group in the Pd(II)-catalyzed β-C–H arylation, alkylation, and methoxylation of carbazole-3-carboxamide, carbazole-2-carboxamide substrates. An ample number of β-C–H arylated, alkylated, benzylated, and methoxylated carbazole-3-carboxamides were synthesized. The structures of representative β-C(2)–H arylated carbazole and β-C(2)–H methoxylated carbazole motifs were unequivocally confirmed by single-crystal X-ray structure analysis. Given the wide range of applications of carbazoles in chemistry, materials sciences, and medicinal chemistry and there have been constant efforts for developing new methods for synthesizing functionalized carbazoles. This work contributes to the expansion of the library of C2,C3,C4-functionalized carbazole motifs through a Pd(II)-catalyzed directing-group-aided site-selective β-C–H activation and functionalization of carbazole-3-carboxamides.

Tuning the Photophysical Properties and Photostability of Bis(naphthobipyrrolylmethene) Derived BODIPY via Functionalization.

A series of NIR absorbing and emitting, naphthobipyrrole derived BODIPY dyes are reported. These dyes possess different functional groups viz. -CHO, -CN, -NO2 , -Br and Ph at its α,α'-positions. All the derivatives were characterized thoroughly via various spectroscopic means as well as single-crystal X-ray structural analyses. Impacts of functionalization on its photophysical properties as well as photostability were evaluated. For instance, incorporation of the phenyl moieties at the α, α'-positions by Suzuki coupling of the dibromo-derivative 4 with phenyl boronic acid led to substantial bathochromic shift in absorption (762 vs 727 nm) and emission (778 vs 744 nm) relative to the unsubstituted parent dye VI. Theoretical calculations have been performed by ground state optimization to evaluate the electronic transitions which supports experimental observation.

Electron-Rich MoIV 3 -Polyoxomolybdates Resembling the Paratungstic Archetype.

The first polyoxometalates (POMs) composed of MoIV , MoV 2 , discrete d1 -MoV and MoVI , [MoIV 3 MoV 6 MoVI 4 O32 (μ2 -OH)(μ3 -OH)py9 ] (1), was prepared from the solvothermal partial oxidation of [MoIV 3 O2 (O2 CCH3 )6 (H2 O)3 ]ZnCl4 in a mixture of pyridine and water. The MoV =O adduct-free unit [H2 Mo12 O33 py9 ] presents the 11e-reduced Mo derivative of the paratungtic archetype. The use of methanol, ethanol, n-propyl alcohol and triglycol instead of water produced the isostructural [MoIV 3 MoV 6 MoVI 4 O32 (μ3 -OH)(μ2 -OR)py9 ](R=CH3 , 2; C2 H5 , 3; C3 H7 , 4; C2 H4 OH, 5), providing the first examples of MoIV 3 -POMs containing bridging alkoxyl groups. The addition of [CrIII Mo6 O24 ]9- led to the substitution of {MoV =O}3+ with {CrIII -py}3+ in the allomer [MoIV 3 MoV 5 MoVI 4 CrIII O32 (μ-OH)2 py10 ] (6). Using a mixture of Mo3 and MoW2 precursors afforded WVI -incorporated allomer [MoIV 3 MoV 6 MoVI WVI 3 O32 (μ-OH)2 py9 ] (7). The complete substitution of MoVI with WVI by using a mixture of the Mo2 W, MoW2 and W3 precursors produced the diamagnetic [MoIV 3 MoV 6 WVI 4 O33 (μ3 -OH)py9 ]- (syn-8) resulting from the anti→syn conversion between the top and bottom M3 triads concomitant with MoV -MoV bonding. Both anti-1-7 and syn-8 have been characterized by X-ray single crystal structural analyses. The spin distribution and magnetic interactions have been investigated by temperature-dependent magnetic susceptibility and DFT theoretical calculations. Heterogeneous hydrogen transfer catalysis has been examined by the Lewis catalysis field (LCF) theory.

Coupling Pyrazine to Dithiocarbonates for Molybdopterin Model Ligands—Indispensable Tin

Several synthetic cross-coupling procedures were (re-)evaluated for the tethering of pyrazine to dithiocarbonates. The resultant species constitute pro-ligands and can be converted by removal of the C=O moiety into ene-dithiolate ligand systems that model molybdopterin. The coupling of 2-iodopyrazine with the stannylated dithiocarbonate units mediated by copper(I)-thiophene-2-carboxylate in stoichiometric equivalents proved to be the most efficient and the only reliable route to the targeted compounds. Single-crystal X-ray structural analysis confirmed the final structures of two pursued pyrazine-derived dithiocarbonates and those of two intermediates.

Synthesis of Hexahydropyrrolo-isoquinolines by 1,3-Dipolar cycloaddition of tetrahydroisoquinolines and cinnamaldehydes

A new method is described for the synthesis of hexahydropyrrolo-isoquinolines through the 1,3-dipolar cycloaddition of cinnamaldehydes with azomethine ylides generated from cinnamaldehydes and tetrahydroisoquinolines. The carbonyl CO groups of cinnamaldehydes serve as the precursor for the generation of azomethine ylides and the CC double bonds of cinnamaldehyde act as the dipolarophiles in the cycloaddition. The key features are easily available substrates, good functional group tolerance and mild reaction conditions. The relative configurations of products are confirmed by X-ray single crystal structure analysis, and a possible mechanism is proposed. A gram-scale experiment and some chemical transformations were conducted to show the synthetic utility of this approach. Finally, a plausible mechanism was proposed to clarify the formation of products with different configurations.

Elucidation of Degradation Behavior of Hydroxy Group-Containing Benzodiazepines in Artificial Gastric Juice: Study on Degradability of Drugs in Stomach (III).

The degradation behavior of three benzodiazepines (BZPs)-lormetazepam (LMZ), lorazepam, and oxazepam-with hydroxy groups on the diazepine ring in artificial gastric juice and the effect of storage pH conditions on drug degradability were monitored using an LC/photodiode array detector (PDA) to estimate their pharmacokinetics in the stomach. Although the three BZPs degraded in artificial gastric juice, none could be restored, despite increasing the storage pH, implying that the degradation reaction was irreversible. As for LMZ, we discussed the physicochemical parameters, such as the activation energy and activation entropy involved in the degradation reaction as well as the reaction kinetics; one of the degradation products was isolated and purified for structural analysis. In the LMZ degradation experiment, peaks corresponding to degradation products, (A) and (B), were detected through the LC/PDA measurements. Regarding the degradation behavior, we hypothesized that LMZ was degraded into (B) via (A), where (A) was an intermediate and (B) was the final product. Although the isolation of degradation product (A) was challenging, degradation product (B) could be isolated and was confirmed to be "methanone, [5-chloro-2-(methylamino)phenyl](2-chlorophenyl)-" based on structure determination using various instrumental analyses. The compound exhibited axis asymmetry as determined using single-crystal X-ray structure analysis. Because the formation of degradation product (B) was irreversible, it would be prudent to target the final degradation product (B) and LMZ for identification when detecting LMZ in human stomach contents, such as during forensic dissection.

A new lithium barium aluminum oxide fluoride, LiBa2AlO3F2

Single-crystal grains of a new quinary compound, LiBa2AlO3F2, were obtained from a polycrystalline sample prepared by heating a starting binary oxide and fluoride mixture with a composition richer in Li and Al than the stoichiometric composition at 1023 ​K. Single-crystal X-ray structure analysis revealed that LiBa2AlO3F2 crystallizes in an orthorhombic cell (a ​= ​7.9953 (3) Å, b ​= ​11.7763 (4) Å, c ​= ​5.6090 (2) Å, space group Pbcm). Al-centered O tetrahedra form zigzag chains in the c-axis direction by sharing vertex oxygen atoms. An OF4 four-sided pyramid is formed, and a Li atom is situated in the pyramid and near the F4 basement. A Li-OF4 pyramid layer is formed by sharing F atoms of the pyramid at x ∼0 around the (100) plane. Ba atoms are located between the slab of Al–O4 zigzag chains and the Li–OF4 pyramid layer. Rietveld analysis of the powder X-ray diffraction pattern indicated that a single-phase polycrystalline bulk sample of LiBa2AlO3F2 was synthesized from a starting-materials mixture with the stoichiometric composition. The conductivity measured for the sample prepared at 1173 ​K was 2.6 ​× ​10−9 ​S ​cm−1 ​at 301 ​K and 2.9 ​× ​10−6 ​S ​cm−1 ​at 443 ​K, and the Li+ transport number was 99%. LiBa1.94Eu0.06AlO3F2 was synthesized by partial substitution of Eu2+ for Ba2+. A broad emission spectrum with a peak at 610 ​nm and a full-width at half-maximum of 170 ​nm was recorded for this sample under ultraviolet-light excitation at a wavelength of 330 ​nm.

Electrochemical sensor for determination of butylated hydroxyanisole in real samples using glassy carbon electrode modified by [Co(HL)2Cl2] nano-complex.

A new mononuclear Co(II) complex with the formula [Co(HL)2Cl2] (1) (HL= N-(2-hydroxy-1-naphthylidene)-2-methyl aniline) has been synthesized and characterized by Fourier transform infrared spectroscopy, UV-Vis, elemental analysis and single crystal X-ray structure analysis. Single crystals of the complex [Co(HL)2Cl2] (1) were obtained through slow evaporation of an acetonitrile solution at room temperature. The crystal structure analysis revealed that the two Schiff base ligands create a tetrahedral geometry via oxygen atoms and two chloride atoms. The nano-size of [Co(HL)2Cl2] (2) have been synthesized by the sonochemical process. Characterization of nanoparticles (2) was carried out via X-ray powder diffraction (XRD), scanning electron microscopy (SEM), UV-Vis, and FT-IR spectroscopy. The average sample size synthesized via the sonochemical method was approximately 56 nm. In this work, a simple sensor based on a glassy carbon electrode modified with [Co(HL)2Cl2] nano-complex was developed ([Co(HL)2Cl2] nano-complex/GCE) for convenient and fast electrochemical detection of butylated hydroxyanisole (BHA). The modified electrode offers considerably improved voltammetric sensitivity toward BHA compared to the bare electrode. Applying linear differential pulse voltammetry, a good linear relationship of the oxidation peak current with respect to concentrations of BHA across the range of 0.5-150 μM and a detection limit of 0.12 μM was achieved. The [Co(HL)2Cl2] nano-complex/GCE sensor was applied to the determination of BHA in real samples successfully.

Effect of Functional Groups at N-Terminus on the Properties and Structures of Crystalline Nano-Cavities in Flexible Peptide Ni(II)-Macrocycles

Abstract To clarify the design strategy for achieving functionality in crystalline multi-component systems comprising cyclic complexes of flexible short peptides, crystalline Ni(II) cyclic complexes were synthesized using two novel dipeptides (2 and 3) possessing different functional groups at the N-terminus of dipeptide 1. X-ray single-crystal structural analysis revealed that 2 and 3 formed tetranuclear cyclic complexes ([Ni4L4]8+), which were also observed for 1. The crystalline packing structure of the cyclic complexes of dipeptide 2 was almost the same as that of the cyclic complexes of dipeptide 1, whereas that of 3 had a different packing structure. The cooperative opening/closing of the crystalline heterogeneous cavity, which demonstrates humidity-responsive cooperative binding in the cyclic complexes of 1, was not observed for the complexes of 2, plausibly because of the decrease in crystalline voids of the latter. In contrast, the amounts for water and alcohol vapor adsorbed at room temperature were almost the same for the open forms of the cyclic complexes of 1 and 2, which was supported by the expansion of the flexible cavities in the crystalline cyclic complexes of 2.

An Inorganic-Organic Hybrid Framework Composed of Polyoxotungstate and Long-Chained Bolaamphiphile.

Surfactants are functional molecules utilized in various situations. The self-assembling property of surfactants enables several molecular arrangements that can be employed to build up nanometer-sized architectures. This is beneficial in the construction of functional inorganic-organic hybrids holding the merits of both inorganic and organic components. Among several surfactants, bolaamphiphile surfactants with two hydrophilic heads are effective, as they have multiple connecting or coordinating sites in one molecule. Here, a functional polyoxotungstate inorganic anion was successfully hybridized with a bolaamphiphile to form single crystals with anisotropic one-dimensional alignment of polyoxotungstate. Keggin-type metatungstate ([H2W12O40]6-, H2W12) was employed as an inorganic anion, and 1,12-dodecamethylenediammonium (C12N2) derived from 1,12-dodecanediamine was combined as an organic counterpart. A simple and general ion-exchange reaction provided a hybrid crystal consisting of H2W12 and C12N2 (C12N2-H2W12). Single crystal X-ray structure analyses revealed a characteristic honeycomb structure in the C12N2-H2W12 hybrid crystal, which is possibly effective for the emergence of conductivity due to the dissociative protons of C12N2.

Revisiting the bromination of 3β-hydroxycholest-5-ene with CBr4/PPh3 and the subsequent azidolysis of the resulting bromide, disparity in stereochemical behavior.

Cholesterol reacts under Appel conditions (CBr4/PPh3) to give 3,5-cholestadiene (elimination) and 3β-bromocholest-5-ene (substitution with retention of configuration). Thus, the bromination of cholesterol deviates from the stereochemistry of the standard Appel mechanism due to participation of the Δ5 π-electrons. In contrast, the subsequent azidolysis (NaN3/DMF) of 3β-bromocholest-5-ene proceeds predominantly by Walden inversion (SN2) affording 3α-azidocholest-5-ene. The structures of all relevant products were revealed by X-ray single crystal structure analyses, and the NMR data are in agreement to the reported ones. In light of these findings, we herein correct the previous stereochemical assignments reported by one of us in the Beilstein J. Org. Chem. 2015, 11, 1922-1932 and the Monatsh. Chem. 2018, 149, 505-517.

Low-Dimensional Compounds Containing Bioactive Ligands. Part XX: Crystal Structures, Cytotoxic, Antimicrobial Activities and DNA/BSA Binding of Oligonuclear Zinc Complexes with Halogen Derivatives of 8-Hydroxyquinoline

Two tetranuclear [Zn4Cl2(ClQ)6]·2DMF (1) and [Zn4Cl2(ClQ)6(H2O)2]·4DMF (2), as well as three dinuclear [Zn2(ClQ)3(HClQ)3]I3 (3), [Zn2(dClQ)2(H2O)6(SO4)] (4) and [Zn2(dBrQ)2(H2O)6(SO4)] (5), complexes (HClQ = 5-chloro-8-hydroxyquinoline, HdClQ = 5,7-dichloro-8-hydroxyquinoline and HdBrQ = 5,7-dibromo-8-hydroxyquinoline) were prepared as possible anticancer or antimicrobial agents and characterized by IR spectroscopy, elemental analysis and single crystal X-ray structure analysis. The stability of the complexes in solution was verified by NMR spectroscopy. Antiproliferative activity and selectivity of the prepared complexes were studied using in vitro MTT assay against the HeLa, A549, MCF-7, MDA-MB-231, HCT116 and Caco-2 cancer cell lines and on the Cos-7 non-cancerous cell line. The most sensitive to the tested complexes was Caco-2 cell line. Among the tested complexes, complex 3 showed the highest cytotoxicity against all cell lines. Unfortunately, all complexes showed only poor selectivity to normal cells, except for complex 5, which showed a certain level of selectivity. Antibacterial potential was observed for complex 5 only. Moreover, the DNA/BSA binding potential of complexes 1–3 was investigated by UV-vis and fluorescence spectroscopic methods.

Two Novel Schiff Base Manganese Complexes as Bifunctional Electrocatalysts for CO2 Reduction and Water Oxidation.

One mononuclear Mn(III) complex [MnIIIL(H2O)(MeCN)](ClO4) (1) and one hetero-binuclear complex [(CuIILMnII(H2O)3)(CuIIL)2](ClO4)2·CH3OH (2) have been synthesized with the Schiff base ligand (H2L = N,N'-bis(3-methoxysalicylidene)-1,2-phenylenediamine). Single crystal X-ray structural analysis manifests that the Mn(III) ion in 1 has an octahedral coordination structure, whereas the Mn(II) ion in 2 possesses a trigonal bipyramidal configuration and the Cu(II) ion in 2 is four-coordinated with a square-planar geometry. Electrochimerical catalytic investigation demonstrates that the two complexes can electrochemically catalyze water oxidation and CO2 reduction simultaneously. The coordination environments of the Mn(III), Mn(II), and Cu(II) ions in 1 and 2 were provided by the Schiff base ligand (L) and labile solvent molecules. The coordinately unsaturated environment of the Cu(II) center in 2 can perfectly facilitate the catalytic performance of 2. Complexes 1 and 2 display that the over potentials for water oxidation are 728 mV and 216 mV, faradaic efficiencies (FEs) are 88% and 92%, respectively, as well as the turnover frequency (TOF) values for the catalytic reduction of CO2 to CO are 0.38 s-1 at -1.65 V and 15.97 s-1 at -1.60 V, respectively. Complex 2 shows much better catalytic performance for both water oxidation and CO2 reduction than that of complex 1, which could be owing to a structural reason which is attributed to the synergistic catalytic action of the neighboring Mn(III) and Cu(II) active sites in 2. Complexes 1 and 2 are the first two compounds coordinated with Schiff base ligand for both water oxidation and CO2 reduction. The finding in this work can offer significant inspiration for the future development of electrocatalysis in this area.

Solid-state Thermal Transformation of Methylammonium Monomolybdate to Polyoxomolybdates and their Applications as Staining Reagents for Transmission Electron Microscopy Observations of Viruses

The solid-state heating of methylammonium monomolybdate, (CH3NH3)2[MoO4] (prepared by dissolving MoO3 in an aqueous methylamine solution), in air released methylamine and water to produce (CH3NH3)6[Mo7O24] and followed by (CH3NH3)8[Mo10O34] before transformation to MoO3. We report the first single-crystal X-ray structural analysis of (CH3NH3)2[MoO4] and (CH3NH3)6[Mo7O24] and demonstrate that the decamolybdate structure is different from that obtained from ammonium molybdates. Furthermore, (CH3NH3)6[Mo7O24] is a good negative staining reagent for transmission electron microscopy observations of viruses, such as SARS-CoV-2 and influenza virus.

Supramolecular Recognition within a Nanosized "Buckytrap" That Exhibits Substantial Photoconductivity.

We report here a nanosized "buckytrap", 1, constructed from two bis-zinc(II) expanded-TTF (exTTF) porphyrin subunits. Two forms, 1a and 1b, differing in the axial ligands, H2O vs tetrahydrofuran (THF), were isolated and characterized. Discrete host-guest inclusion complexes are formed upon treatment with fullerenes as inferred from a single-crystal X-ray structural analyses of 1a with C70. The fullerene is found to be encapsulated within the inner pseudohexagonal cavity of 1a. In contrast, the corresponding free-base derivative (2) was found to form infinite ball-and-socket type supramolecular organic frameworks (3D-SOFs) with fullerenes, (2•C60)n or (2•C70)n. This difference is ascribed to the fact that in 1a and 1b the axial positions are blocked by a H2O or THF ligand. Emission spectroscopic studies supported a 1:1 host-guest binding stoichiometry, allowing association constants of (2.0 ± 0.5) × 104 M-1 and (4.3 ± 0.9) × 104 M-1 to be calculated for C60 and C70, respectively. Flash-photolysis time-resolved microwave conductivity (FP-TRMC) studies of solid films of the Zn-complex 1a revealed that the intrinsic charge carrier transport, i.e., pseudo-photoconductivity (ϕ∑μ), increases upon fullerene inclusion (e.g., ϕ∑μ = 1.53 × 10-4 cm2 V-1 s-1 for C60⊂(1a)2 and ϕ∑μ = 1.45 × 10-4 cm2 V-1 s-1 for C70⊂(1a)2 vs ϕ∑μ = 2.49 × 10-5 cm2 V-1 s-1 for 1a) at 298 K. These findings provide support for the notion that controlling the nature of self-assembly supramolecular constructs formed from exTTF-porphyrin dimers through metalation or choice of fullerene can be used to regulate key functional features, including photoconductivity.

Pentagon-Fused Sumanenes on the Aromatic Peripheries en Route to the Bottom-Up Synthesis of Fullerenes

AbstractBowl-shaped π-conjugated sumanenyltriamines were successfully synthesized in a one-step reaction from bromomethylsumanene. This molecule represents an example of hemiazafullerene (C54N6 fragment) with six isolated pentagons. Its single-crystal X-ray structural analysis showed the formation of one-dimensional columnar structures incorporating chloroform. The hemifullerene (C30 fragment) was also synthesized when the nucleophile was changed to dimethylmalonate.

Host-guest system of a phosphorylated macrocycle assisting structure determination of oily molecules in single-crystal form.

X-ray crystallography is the most reliable method for structure elucidation and absolute configuration determination of organic molecules based on their single-crystal forms. However, many analytes are hard to crystallize because of their low melting points (an oily state at room temperature) or conformational flexibility. Here, we report the crystallization of a macrocycle, CTX[P(O)Ph] (host), which is a cyclotrixylohydroquinoylene (CTX) derivative, with 26 oily organic molecules (guests), which is applied for the structural determination of the guest with X-ray crystallography. With the aid of the host, CTX[P(O)Ph], the guest molecules were well-ordered with full occupancy in crystal structures. In most cases, at least one guest structure without any disorder could be observed; solvent masking was not necessary for the single crystal X-ray structural analysis, and thus the structures of the guests could be successfully determined, and the absolute configuration could be assigned reliably for chiral guests with this method. The crystallization mechanism was further discussed from theoretical and experimental perspectives, suggesting that the negative electrostatic potential surface of CTX[P(O)Ph] and noncovalent interactions between the host and guest were crucial for the ordered arrangements of the guest.

Synthesis, spectral, structural and DFT studies on Tl(III) dithiocarbamate complexes: Preparation of Tl2S nanoparticles from tris(N-benzyl-N-furfuryldithiocarbamato-S,S’)thallium(III)

Tris(N,N-difurfuryldithiocarbamato-S,S’)thallium(III) (1), tris(N-benzyl-N-furfuryldithiocarbamato-S,S’)thallium(III) (2) and tris(N-furfuryl-N-(2-phenylethyl)dithiocarbamato-S,S’)thallium(III) (3) have been prepared and characterized by elemental analysis, IR and NMR (1H and 13C) spectroscopy. Single crystal X-ray structural analysis was carried out for 1. X-ray crystallography revealed that complex 1 is monomer. Thallium is hexacoordinated with six sulfur atoms from three chelating N,N-difurfuryl dithiocarbamate ligands in a distorted octahedral geometry. Complex 1 is further stabilized by various interactions such as CH…π (chelate), CH…π, CH…S and CH…O interactions. CH…O interactions lead to the formation of 18 membered macrocyclic ring. Hirshfeld surface analysis (dnorm surface and 2-D fingerprint plots) were performed using Crystal explorer 3.1 program. The major contributions for the crystal packing are from H…H, S…H/H…S, O…H/H…O and C…H/H…C interactions. Molecular optimization, molecular electrostatic potential and frontier molecular orbitals were calculated using DFT method for 1. DFT calculations on 1 revealed that HOMO was localized predominantly over furfuryl ring carbon atoms, whilst the LUMO was located on Tl and S atoms, with the HOMO-LUMO energy gap being 2.5067 eV. Thallium sulfide nanoparticles Tl2S-1 and Tl2S-2 have been prepared from complex 2 using conventional heating and microwave irradiation, respectively. The as-prepared Tl2S nanoparticles have been characterized by PXRD, EDS, HR-TEM, UV–vis absorption and fluorescence spectroscopy. The X-ray diffraction pattern confirms the rhombohedral phase of as-prepared Tl2S.

Pd-catalyzed decarboxylative 1,4-addition reactions of benzofuran-based azadienes with allyl phenyl carbonates.

Under the catalysis of Pd(OAc)2/dppf/Na2CO3, the decarboxylative 1,4-addition reaction of benzofuran-based azadienes with allyl phenyl carbonates took place easily and delivered the desired products in reasonable chemical yields. The chemical structure of the target compounds was clearly identified by single crystal X-ray structural analysis.

One silicon atom of bis(silylene) functions as a selective Lewis base under adduct formation with a Lewis acid.

Herein, we describe the facile and selective one-pot synthetic route to silylene-aluminum and silylene-gallium adducts. Reduction of silylene LSiCl (L = PhC(NtBu)2) with KC8 in the presence of bulky and sterically hindered cyclopentadienyl aluminum Cp'''AlCl2 (Cp''' = 1,2,4-tBu3C5H2) and gallium [η1-Cp'''Ga(μ-Cl)Cl]2 to afford the Lewis acid-base adducts η1-Cp'''M(Cl2) ← Si(L)-SiL (M = Al, 1; M = Ga, 3). To confirm the formation of the Lewis acid-base adduct, the bis(silylene) LSi(I)-Si(I)L reacts with Cp'''AlI2 to form η1-Cp'''Al(I2) ← Si(L)-SiL (2). These are the first examples where one Si atom in the bis(silylene) is a Lewis base and coordinates with aluminum or gallium to form a Lewis acid-base adduct, while the other Si atom in the bis(silylene) still maintains the characteristics of silylene. Compound 3 was heated to 70 °C in toluene for 4 hours and decomposed into the silylene LSiCl and Cp'''GaI. Compounds 1-3 are well characterized with NMR spectroscopic methods and single-crystal X-ray structural analysis.