Synthesis, Characterization, and Thermolysis of Dibenzo-7-dimethylgermanorbornadiene

Reversible [4 + 1] Cycloaddition of Arenes by a "Naked" Acyclic Aluminyl Compound

The large steric profile of the N-heterocyclic boryloxy ligand, -OB(NDippCH)2, and its ability to stabilize the metal-centered HOMO, are exploited in the synthesis of the first example of a "naked" acyclic aluminyl complex, [K(2.2.2-crypt)][Al{OB(NDippCH)2}2]. This system, which is formed by substitution at AlI (rather than reduction of AlIII), represents the first O-ligated aluminyl compound and is shown to be capable of hitherto unprecedented reversible single-site [4 + 1] cycloaddition of benzene. This chemistry and the unusual regioselectivity of the related cycloaddition of anthracene are shown to be highly dependent on the availability (or otherwise) of the K+ countercation.

Recent advances in the chemistry of isolable carbene analogues with group 13-15 elements

Carbenes (R2C:), compounds with a divalent carbon atom containing only six valence shell electrons, have evolved into a broader class with the replacement of the carbene carbon or the RC moiety with main group elements, leading to the creation of main group carbene analogues. These analogues, mirroring the electronic structure of carbenes (a lone pair of electrons and an empty orbital), demonstrate unique reactivity. Over the last three decades, this area has seen substantial advancements, paralleling the innovations in carbene chemistry. Recent studies have revealed a spectrum of unique carbene analogues, such as monocoordinate aluminylenes, nitrenes, and bismuthinidenes, notable for their extraordinary properties and diverse reactivity, offering promising applications in small molecule activation. This review delves into the isolable main group carbene analogues that are in the forefront from 2010 and beyond, spanning elements from group 13 (B, Al, Ga, In, and Tl), group 14 (Si, Ge, Sn, and Pb) and group 15 (N, P, As, Sb, and Bi). Specifically, this review focuses on the potential amphiphilic species that possess both lone pairs of electrons and vacant orbitals. We detail their comprehensive synthesis and stabilization strategies, outlining the reactivity arising from their distinct structural characteristics.

Intramolecular dearomative 1,4-addition of silyl and germyl radicals to a phenyl moiety

Herein, we present that the radicals [Ph3PC(Me)EMes2]˙ (2Si and 2Ge) can be generated from the α-silylated and α-germylated phosphorus ylides Ph3PC(Me)E(Cl)Mes2 (1Si and 1Ge) through one-electron reduction with Jones' dimer (MesNacNacMg)2 in benzene. Although isolation of the free radicals was not possible, the products of the intramolecular addition of the radicals to a phenyl substituent of the phosphorus moiety, followed by subsequent reaction with 2Si or 2Ge to the isolated species 3Si and 3Ge, respectively, were observed. This transformation witnesses a dearomative 1,4-addition of tetryl radical species to the phenyl scaffold in a stereoselective anti-fashion.

Crystal structure and synthesis of the bis(anthracene)dicuprate dianion as the dipotassium salt, [K(tetrahydrofuran)2]2[{Cu(9,10-η2-anthracene)}2], the first anionic arene complex of copper

Reactions of (tricyclohexylphosphane)copper(I) chloride with two equivalents of potassium anthracene (KAn) in tetrahydrofuran (THF) at 200 K provides air-sensitive but thermally stable (at 293 K) solutions from which yellow crystalline blocks of bis[bis(tetrahydrofuran-κO)potassium] bis(μ-anthracene-κ2C9:C10)dicopper, [K(THF)2]2[{Cu(9,10-η2-C14H10)}2] or [K(C4H8O)2]2[Cu2(C14H10)2], 1, were isolated in about 50% yield. Single-crystal X-ray crystallographic analysis of 1 confirmed the presence of the first known (arene)cuprate. Also, unlike all previously known homoleptic (anthracene)metallates of d-block elements, which contain metals coordinated only to terminal rings, the organocuprate unit in 1 contains copper bound to the 9,10-carbons of the central ring of anthracene. No other d- or f-block metal is known to afford an anthracene or other aromatic hydrocarbon complex having the architecture of organodicuprate 1.

Dearomatization of C6 Aromatic Hydrocarbons by Main Group Complexes

The dearomatization reaction is a powerful method for transformation of simple aromatic compounds to unique chemical architectures rapidly in synthetic chemistry. Over the past decades, the chemistry in this field has evolved significantly and various important organic compounds such as crucial bioactive molecules have been synthesized through dearomatization. In general, photochemical conditions or assistance by transition metals are required for dearomatization of rigid arenes. Recently, main-group elements, especially naturally abundant elements in the Earth's crust, have attracted attention as they have low toxicity and are cost-effective compared to the late transition metals. In recent decades, a variety of low-valent main-group molecules, which enable the activation of stable aromatic compounds under mild conditions, have been developed. This minireview highlights the developments in the chemistry of dearomatization of C6 aromatic hydrocarbons by main-group compounds leading to the formation of seven-membered EC6 (E=main-group elements) ring or cycloaddition products.

Actinide arene-metalates: ion pairing effects on the electronic structure of unsupported uranium-arenide sandwich complexes

Addition of [UI₂(THF)₃(μ-OMe)]₂·THF (2·THF) to THF solutions containing 6 equiv. of K[C₁₄H₁₀] generates the heteroleptic dimeric complexes [K(18-crown-6)(THF)₂]₂[U(η⁶-C₁₄H₁₀)(η⁴-C₁₄H₁₀)(μ-OMe)]₂·4THF (118C6·4THF) and {[K(THF)₃][U(η⁶-C₁₄H₁₀)(η⁴-C₁₄H₁₀)(μ-OMe)]}₂ (1THF) upon crystallization of the products in THF in the presence or absence of 18-crown-6, respectively. Both 118C6·4THF and 1THF are thermally stable in the solid-state at room temperature; however, after crystallization, they become insoluble in THF or DME solutions and instead gradually decompose upon standing. X-ray diffraction analysis reveals 118C6·4THF and 1THF to be structurally similar, possessing uranium centres sandwiched between bent anthracenide ligands of mixed tetrahapto and hexahapto ligation modes. Yet, the two complexes are distinguished by the close contact potassium-arenide ion pairing that is seen in 1THF but absent in 118C6·4THF, which is observed to have a significant effect on the electronic characteristics of the two complexes. Structural analysis, SQUID magnetometry data, XANES spectral characterization, and computational analyses are generally consistent with U(iv) formal assignments for the metal centres in both 118C6·4THF and 1THF, though noticeable differences are detected between the two species. For instance, the effective magnetic moment of 1THF (3.74 μ_B) is significantly lower than that of 118C6·4THF (4.40 μ_B) at 300 K. Furthermore, the XANES data shows the U L_III-edge absorption energy for 1THF to be 0.9 eV higher than that of 118C6·4THF, suggestive of more oxidized metal centres in the former. Of note, CASSCF calculations on the model complex {[U(η⁶-C₁₄H₁₀)(η⁴-C₁₄H₁₀)(μ-OMe)]₂}²⁻ (1*) shows highly polarized uranium–arenide interactions defined by π-type bonds where the metal contributions are primarily comprised by the 6d-orbitals (7.3 ± 0.6%) with minor participation from the 5f-orbitals (1.5 ± 0.5%). These unique complexes provide new insights into actinide–arenide bonding interactions and show the sensitivity of the electronic structures of the uranium atoms to coordination sphere effects.

Use of Chatt metal-arene protocols with uranium leads to the synthesis of the first well-characterized, unsupported actinide–arenide sandwich complexes. The electronic structures of the actinide centres show a key sensitivity to ion pairing effects.

Sulfur monoxide thermal release from an anthracene-based precursor, spectroscopic identification, and transfer reactivity

Sulfur monoxide (SO) is a highly reactive molecule and thus, eludes bulk isolation. We report here on synthesis and reactivity of a molecular precursor for SO generation, namely 7-sulfinylamino-7-azadibenzonorbornadiene (1). This compound has been shown to fragment readily driven by dinitrogen expulsion and anthracene formation on heating in the solid state and in solution, releasing SO at mild temperatures (<100 °C). The generated SO was detected in the gas phase by MS and rotational spectroscopy. In solution, 1 allows for SO transfer to organic molecules as well as transition metal complexes.