Stannabenzenylpotassium: The First Isolable Tin‐Containing Benzene Derivative

The Reduction of Metallabenzenes: Different Scenarios Highly Dependent on the Central Group 14 Elements, Si vs. Ge

In order to synthesize a silabenzenyl anion, in which the anionic carbon atom of a phenyl anion was replaced with a silicon atom, the reductive dearylation reaction of 1-Tbt-2-tert-butyl-silabenzene (Tbt=2,4,6-tris[bis(trimethylsilyl)methyl]phenyl) with KC8 was attempted. Unexpectedly, this reaction resulted in the formation of a dianion species without the elimination of the Tbt group. This is totally different from the reactions of Tbt-substituted germa- or stannabenzene with KC8 , which resulted in the formation of the corresponding heavy analogues of phenyl anion, together with the elimination of Tbt group. Experimental and theoretical investigation revealed that one of the protons of the o-benzyl positions of the Tbt group was abstracted by the negatively charged silicon atom of an in-situ generated intermediate. Compared with the previously reported germanium system, the contrasting results indicate that the central heavy group 14 element has a great influence on the elimination step of the Tbt group.

Unusual nuclear exchange within a germanium-containing aromatic ring that results in germanium atom transfer

The delivery of single atoms is highly desirable for the straightforward synthesis of complex molecules, however this approach is limited by a lack of suitable atomic transfer reagents. Here, we report a germanium atom transfer reaction employing a germanium analogue of the phenyl anion. The reaction yields a germanium-substituted benzene, along with a germanium atom which can be transferred to other chemical species. The transfer of atomic germanium is demonstrated by the formation of well-defined germanium doped molecules. Furthermore, computational studies reveal that the reaction mechanism proceeds via the first example of an aromatic-to-aromatic nuclear germanium replacement reaction on the germabenzene ring. This unusual reaction pathway was further probed by the reaction of our aromatic germanium anion with a molecular silicon species, which selectively yielded the corresponding silicon-substituted benzene derivative.

Recent progress in the chemistry of heavy aromatics

The aromaticity and synthetic application of "heavy benzenes", i.e., benzenes containing a heavier Group 14 element (Si, Ge, Sn, and Pb) in place of skeletal carbon, have been the targets of many theoretical and synthetic studies. Although the introduction of a sterically demanding substituent enabled us to synthesize and isolate heavy aromatic species as a stable compound by suppressing their high reactivity and tendency to polymerize, the existence of a protection group is an obstruction to the development of functional materials based on heavy aromatics. This review will delineate the most recent topics in the chemistry of heavy aromatics, i.e., the chemistry of "metallabenzenyl anions", which are the heavier Group 14 element analogs of phenyl anions stabilized by taking advantage of charge repulsion instead of steric protection.

Synthesis of Genuine Germenyl Lithiums and the First Persistent Germenyl Radicals

The first isolated genuine germenyl lithiums (R₃Si)(1‐Ad)C=Ge(SiMetBu₂)(Li⋅2 L) (R₃Si=tBu₂MeSi, L=THF (1  a), or L=12‐crown‐4 (1  b) and R₃Si=tBuMe₂Si, L=THF (2  a), or L=12‐crown‐4 (2  b)), were synthesized by reaction of the corresponding acyl germanes 3 and 4, respectively, with tBu₂MeSiLi in THF at 70 °C. The novel 1  a and 2  b were characterized by NMR and UV/Vis spectroscopy, and also by X‐ray crystallography (r(C=Ge)=1.865 Å for 1  a and 1.877 Å for 2  b). Nucleophilic addition reaction of 1  a with MeI and a C−H insertion reactions to the C=Ge bond of 1  a, 2  a and 2  b, are reported. Oxidation of 1  a and 2  b (toluene, 230 K) produces the first persistent germenyl radicals (R₃Si)(1‐Ad)C=Ge⋅‐(SiMetBu₂) (R₃Si=tBu₂MeSi (13  a), R₃Si=tBuMe₂Si (13  b)), which were characterized by EPR spectroscopy (t_1/2≈30 min at 230 K, g=2.029, a_av(⁷³Ge) is 55.0G for 13  a and 60.2G for 13  b). The experimental EPR parameters and DFT calculations indicate that 13  a and 13  b have a strongly bent structure at Ge (calc. ∡(C=Ge−Si)=136.7° (13  a), 135.9° (13  b)), and that the unpaired electron has a substantial s‐character.

Synthesis and Characterization of Rhena[10]annulynes

Most of the reported metallacycles were limited to small cyclic complexes that contain six-membered or smaller rings. Larger-membered metallacycles are still rare and mainly focus on the dimetallacycles. Herein, we...

Heavier element-containing aromatics of [4n+2]-electron systems

While the implication of the aromaticity concept has been dramatically expanded to date since its emergence in 1865, the classical [4n+2]/4n-electron counting protocol still plays an essential role in evaluating the aromatic nature of compounds. Over the last few decades, a variety of heavier heterocycles featuring the formal [4n+2] π-electron arrangements have been developed, which allows for assessing their aromatic nature. In this review, we present recent developments of the [4n+2]-electron systems of heavier heterocycles involving group 13-15 elements. The synthesis, spectroscopic data, structural parameters, computational data, and reactivity are introduced.

An Open-Shell Singlet SnI Diradical and H2 Splitting

The first Sn^I diradical [(ADC^Ph)Sn]₂ (4) based on an anionic dicarbene (ADC^Ph={CN(Dipp)}₂CPh; Dipp=2,6‐iPr₂C₆H₃) scaffold has been isolated as a green crystalline solid by KC₈ reduction of the corresponding bis‐chlorostannylene [(ADC^Ph)SnCl]₂ (3). The six‐membered C₄Sn₂‐ring of 4 containing six π‐electrons shows a diatropic ring current, thus 4 may also be regarded as the first 1,4‐distannabenzene derivative. DFT calculations suggest an open‐shell singlet (OS) ground state of 4 with a remarkably small singlet–triplet energy gap (ΔE_OS–T=4.4 kcal mol⁻¹), which is consistent with CASSCF (ΔE_S–T=6.6 kcal mol⁻¹ and diradical character y=37 %) calculations. The diradical 4 splits H₂ at room temperature to yield the bis‐hydridostannylene [(ADC^Ph)SnH]₂ (5). Further reactivity of 4 has been studied with PhSeSePh and MeOTf.

A Mixed Heavier Si=Ge Analogue of a Vinyl Anion

The versatile reactivities of disilenides and digermenide, heavier analogues of vinyl anions, have significantly expanded the pool of silicon and germanium compounds with various unexpected structural motifs in the past two decades. We now report the synthesis and isolation of a cyclic heteronuclear vinyl anion analogue with a Si=Ge bond, potassium silagermenide as stable thf‐solvate and 18‐c‐6 solvate by the KC₈ reduction of germylene or digermene precursors. Its suitability as synthon for the synthesis of functional silagermenes is proven by the reactions with chlorosilane and chlorophospane to yield the corresponding silyl‐ and phosphanyl‐silagermenes. X‐ray crystallographic analysis, UV/Vis spectroscopy and DFT calculations revealed a significant degree of π‐conjugation between N=C and Si=Ge double bonds in the title compound.

Metallaaromatic Chemistry: History and Development

Since the prediction of the existence of metallabenzenes in 1979, metallaaromatic chemistry has developed rapidly, due to its importance in both experimental and theoretical fields. Now six major types of metallaromatic compounds, metallabenzenes, metallabenzynes, heterometallaaromatics, dianion metalloles, metallapentalenes and metallapentalynes (also termed carbolongs), and spiro metalloles, have been reported and extensively studied. Their parent organic analogues may be aromatic, non-aromatic, or even anti-aromatic. These unique systems not only enrich the large family of aromatics, but they also broaden our understanding and extend the concept of aromaticity. This review provides a comprehensive overview of metallaaromatic chemistry. We have focused on not only the six major classes of metallaaromatics, including the main-group-metal-based metallaaromatics, but also other types, such as metallacyclobutadienes and metallacyclopropenes. The structures, synthetic methods, and reactivities are described, their applications are covered, and the challenges and future prospects of the area are discussed. The criteria commonly used to judge the aromaticity of metallaaromatics are presented.

“Like–like” tetrel bonding interactions between Sn centres: a combinedab initioand CSD study

In this manuscript, we combine a search in the Cambridge Structural Database (CSD) andab initiocalculations (RI-MP2/def2-TZVP level of theory) to analyse the ability of Sn to establish ‘like–like’ tetrel bonding interactions.