A Seven-Membered Aluminum Sulfur Allenyl Heterocycle Arising from the Conversion of an Aluminacyclopropene with CS2

Synthesis and Reactivity of Aluminum Disilacyclopropenes. Cyclic AlSi2 Delocalized 2π Systems

The synthesis, structures, and reactivity of the first unsaturated AlSi2 three-membered ring systems were described. Reactions of dilithiodisilene [(NHB)LiSi═SiLi(NHB)] (1, NHB = diazaborolyl) with aluminum halides AlCl3, Ar(SiMe3)NAlCl2 (Ar = 2,6-iPr2C6H3), Cp*AlBr2 (Cp* = C5Me5), and TipAlBr2·Et2O (Tip = 2,4,6-iPr3C6H2) led to the formation of AlSi2 three-membered ring species, solvated (NHBSi)2AlCl(OEt2) (2) and solvent-free (NHBSi)2AlN(SiMe3) Ar (3), (NHBSi)2AlCp* (4), and (NHBSi)2AlTip (5), in good yields. X-ray diffraction studies and DFT calculations disclosed delocalized AlSi2 2π electron systems. Methanolysis of 4a resulted in cleavage of the Al-Si σ and Si-Si π bonds, giving trihydrodisilane (NHB)H(MeO)SiSiH2 (NHB) (6). Reaction of 4b with 4 equiv of N2O and H2C═CH2 resulted in the insertion of four oxygen atoms and four H2C═CH2 π bonds into all of the Al-Si and Si-Si bonds, yielding the O- and CH2CH2-bridged polycyclic species 7 and 8, demonstrating the synergistic reactivity of the Al-Si and Si-Si bonds in the AlSi2 ring system.

Three-Membered Aluminacycles

Three-membered-ring scaffolds of carbocycles, namely, cyclopropanes and cyclopropenes, are ubiquitous in natural products and pharmaceutical molecules. These molecules exhibit a peculiar reactivity, and their applications as synthetic intermediates and versatile building blocks in organic synthesis have been extensively studied over the past century. The incorporation of heteroatoms into three-membered cyclic structures has attracted significant attention, reflecting fundamental differences in their electronic/geometric structures and reactivities compared to their carbon congeners and their associated potential for exploitation in applications. Recently, the chemistry of low-valent aluminum species, alumylenes, dialumenes, and aluminyl anions, has dramatically developed, which has allowed access to hitherto unprecedented aluminacycles. This Perspective focuses upon advances in the chemistry of three-membered aluminacycles, including their synthetic protocols, spectroscopic and structural properties, and reactivity toward various substrates and small molecules.

Resonance-assisted intramolecular triel bonds

The possibility that the intramolecular Tr⋯S triel bond is strengthened by resonance is examined by quantum chemical calculations within the planar five-membered ring of TrH₂-CRCR-CRS (Tr = Al, Ga, In; R = NO₂, CH₃). This internal bond is found to be rather short (2.4-2.7 Å) with a large bond energy between 12 and 21 kcal mol^-1. The pattern of bond length alternation and atomic charges within the ring is consistent with resonance involving the conjugated double bonds. This resonance enhances the triel bond strength by some 25%. The electron-withdrawing NO₂ group weakens the bond, but it is strengthened by the electron-donating CH₃ substituent. NICS analysis suggests the presence of a certain degree of aromaticity within the ring.

High lignin containing hydrogels with excellent conducting, self-healing, antibacterial, dye adsorbing, sensing, moist-induced power generating and supercapacitance properties

Herein, we design a dynamic redox system of using high contents of lignosulfonate (LS) and Al³⁺ to prepare poly acrylic acid (PAA) (LS-g-PAA-Al) hydrogels. The presence of high LS and Al³⁺ contents, in combination with the effective Al³⁺ complexes formed, renders the resultant hydrogel with some unique attributes, including excellent ionic conductivity (as high as 7.38 S·m^-1) and antibacterial activity; furthermore, a very fast gelation (in 1 min) was obtained. As a flexible strain sensor, the LS-g-PAA-Al hydrogel with high conductivity demonstrates superior sensitivity in human movement detection. In addition, the rich anionic hydrophilic groups, such as sulfonic groups, phenolic hydroxyl groups, in the hydrogels impart the resultant hydrogels with excellent adsorption capacity for cationic dyes: when using Rhodamine B (RB) as a model cationic dye, the adsorption capacity of the resultant hydrogel reaches 334.64 mg·g^-1; as a moist-induced power generator, it generates maximum 150.5 mV open circuit voltage with moist air flow. When the hydrogel electrolyte is assembled into a supercapacitor assembly, it shows high specific capacitance of 245.4 F·g^-1, with the maximum energy density of 21.8 Wh·kg^-1, power density of 2.37 kW·kg^-1, and capacitance retention of 95.1% after 5000 consecutive charge-discharge cycles.

Insertion Chemistry of Lutetacyclopropene toward Unsaturated C-O/C-N Bonds

Although the reaction chemistry of transition metallacyclopropenes has been well-established in the last decades, the reactivity of rare-earth metallacyclopropenes remains elusive. Herein, we report the reaction of lutetacyclopropene 1 toward a series of unsaturated molecules. The reaction of 1 with one equiv. of PhCOMe, Ar¹ CHO (Ar¹ =2,6-Me₂ C₆ H₃ ), W(CO)₆ , and PhCH=NPh provided oxalutetacyclopentenes, metallacyclic lutetoxycarbene, and azalutetacyclopentene via 1,2-insertion of C=O, C≡O, or C=N bonds into Lu-C_sp2 bond, respectively. However, the reaction between 1 and Ar² N=C=NAr² (Ar² =4-MeC₆ H₄ ) gave an acyclic lutetium complex with a diamidinate ligand by the coupling of one molecule of 1 with two carbodiimides, irrespective of the amount of carbodiimide employed. More interestingly, when 1 was treated with two equiv. of Ar¹ CHO, the reductive coupling of two C=O bonds was discovered to give a lutetium pinacolate complex along with the release of tolan. Remarkably, the reactivity of 1 is significantly different from that of scandacyclopropenes; these metallacycles derived from 1 all represent the first cases in rare-earth organometallic chemistry.

Selective Coupling of Lanthanide Metallacyclopropenes and Nitriles via Azametallacyclopentadiene and η2-Pyrimidine Metallacycle

Exploring new lanthanide metallacycles and finding their unique chemistry different from the analogues of transition metals are of great interest and importance. In this work, we reported the synthesis, characterization, and reactivity toward nitriles of two lanthanide metallacyclopropenes: lutetacyclopropene 2a and dysprosacyclopropene 2b. The selective coupling of 2a and three molecules of PhCN was found for the first time to provide the unexpected fused lutetacycle 3a with one 1,6-dihydropyrimidine ring. Mechanistic studies by DFT calculations reveal that the triple insertion of PhCN into 2a proceeds through four key steps: the insertion of the first PhCN into 2a giving azalutetacyclopentadiene IM1, the insertion of the second PhCN into the Lu-N bond of IM1, the intramolecular electrocyclization providing a highly strained η²-pyrimidine metallacycle, and the insertion of the third PhCN into the Lu-C_sp3 bond. Isolation and characterization of two active intermediates, azalutetacyclopentadiene IM1 and η²-pyrimidine dysprosacycle, provide critical evidence for the formation of 3a. Furthermore, IM1 was also reported to react with TMSCN, isocyanides, or W(CO)₆ to furnish the fused [4,5] lutetacycles. The chemistry of two lanthanide metallacyclopropenes with nitriles is significantly different from these metallacyclopropenes of scandium and other metals. Most notably, the azalutetacyclopentadienes, η²-pyrimidine complex, and other metallacycles all represent the first examples in rare-earth organometallic chemistry; the formation of these new lutetacycles provides concrete evidence for understanding the mechanism of transition metal promoted or catalyzed [2+2+2] cycloaddition between alkynes and nitriles.

An Unusual and Facile Synthetic Route to Alumoles

Reaction of the aluminum dialkynyl LAl(CCR)₂ (L=N,N‐chelate ligand and R=organic group) with B(C₆F₅)₃ proceeds through an intermediate with Al⋅⋅⋅η²‐C≡C side‐on coordination to form the alumoles (2, 4, 6). A distinctive reaction pattern indicates a new facile synthetic route to aluminum‐containing heterocycles. The synthetic process is described, and the characterization of compounds and computational calculations were carried out. Furthermore, alumoles 2 and 4 exhibit an aggregation‐induced emission (AIE) of the bright yellow fluorescence.

C−H-Activated Aluminum Hydroxide via Molecular Oxygen

The reaction of LAl[eta2-(C2(SiMe3)2)] (1; L = HC[(CMe)(NDipp)]2, Dipp = 2,6-iPr2C6H3) with dioxygen leads to the elimination of bis(trimethylsilyl)acetylene and the formation of the corresponding aluminum monohydroxide via the oxidation of one of the CHMe2 groups on the Dipp ring.

Formation of aluminacyclobutenes via carbon monoxide and isocyanide insertion

Reaction of LAl[eta2-(CSiMe3)2] (L = HC[(CMe)(NAr)]2, Ar = 2,6-iPr2C6H3) with carbon monoxide and tert-butyl isocyanide afforded unique AlC3 aluminacyclobutenes via insertion into one of the aluminium-carbon bonds.

Bimetallic Anilido-Aldimine Zinc Complexes for Epoxide/CO2 Copolymerization

Acyclic o-phenylene-bridged bis(anilido-aldimine) compounds, o-C(6)H(4){C(6)H(2)R(2)N=CH-C(6)H(4)-(H)N(C(6)H(3)R'(2))}(2) and related 30-membered macrocyclic compounds, o-C(6)H(4){C(6)H(2)R'(2)N=CH-C(6)H(4)-(H)N-C(6)H(2)R(2)}(2) (o-C(6)H(4)) are prepared. Successive additions of Me(2)Zn and SO(2) gas to the bis(anilido-aldimine) compounds afford quantitatively dinuclear mu-methylsulfinato zinc complexes, o-C(6)H(4){(C(6)H(2)R(2)N=CH-C(6)H(4)-N(C(6)H(3)R'(2))-kappa(2)-N,N)Zn(mu-OS(O)Me)}(2) (R = iPr and R' = iPr, 29; R = Et and R' = Et, 30; R = Me and R'= Me, 31; R = Me and R' = iPr, 32; R = Et and R' = Me, 33; R = Et and R' = iPr, 34; R = iPr and R' = Et, 35) and o-C(6)H(4){C(6)H(2)R'(2)N=CH-C(6)H(4)-N-C(6)H(2)R(2)-kappa(2)-N,N)Zn(mu-OS(O)Me)}(2) (o-C(6)H(4)) (R = Et and R'= Et, 36; R = Me and R' = Me, 37; R = iPr and R' = Me, 38; R = Et and R' = Me, 39; R = Me and R'= iPr, 40). Molecular structures of 34 and 40 are confirmed by X-ray crystallography. Complexes 30-35 show high activity for cyclohexene oxide/CO(2) copolymerization at low [Zn]/[monomer] ratio (1:5600), whereas the complex of mononucleating beta-diketiminate {[(C(6)H(3)Et(2))N=C(Me)CH=C(Me)N(C(6)H(3)Et(2))]Zn(mu-OS(O)Et)}(2) shows negligible activity in the same condition. Activity is sensitive to the N-aryl ortho substituents and the highest activity is observed with 32. Turnover number up to 2980 and molecular weight (M(n)) up to 284 000 are attained with 32 at such a highly diluted condition as [Zn]/[monomer] = 1:17 400. Macrocyclic complexes 36-40 show negligible activity for copolymerization.

Chemistry of aluminium(i)

In this article, we discuss the synthesis of tetrameric and monomeric aluminium(I) compounds. These compounds are prepared by reduction of the respective Al-X (X = halide) bond containing precursor. The tetrameric aluminium(I) compounds are synthesized by using sterically bulky ligands whereas a stable monomeric aluminium(I) compound is obtained using a monovalent chelating ligand. Theoretical studies are carried out on the monomer to understand the Lewis basicity. The presence of a lone pair of electrons plays an important role in the preparation of aluminium containing heterocyclic compounds, main group-main group and transition metal-main group compounds having donor-acceptor bonds by carrying out reactions with unsaturated compounds and Lewis acids.