Arylboronic Acid Pinacol Esters as Stable Boron Sources for Dihydrodibenzoborepin Derivatives and a Dibenzoborole.

The general synthesis of boron-containing cyclic compounds (boracycles) necessitates toxic organotin precursors or highly reactive boron halides. Here, we report the synthesis of seven- and five-membered boracycles utilizing arylboronic acid pinacol esters (ArBpins) as stable boron sources. Grignard reagents generated from 2,2'-dibromodibenzyl or 2,2'-dibromobiphenyl reacted with ArBpins, where Ar = 9-anthryl (Anth), 2,4,6-trimethylphenyl (Mes), or 2,4,6-triisopropylphenyl (Tip), to give 10,11-dihydro-5-dibenzo[,]borepins or dibenzoborole derivatives.

Inorganic salt-assisted assembly of anionic π-conjugated rings enabling Li NMR-based evaluation of antiaromaticity.

The H NMR-based estimation of antiaromaticity in anionic molecules is challenging because of the difficulty in separately evaluating NMR shielding effects due to paratropic ring currents and negative charges. Herein we propose a novel approach for the Li NMR-based evaluation of antiaromaticity enabled by inorganic salt-assisted clusterization, which is serendipitously found during our studies on hyperconjugative antiaromaticity. Reduction of a dibenzo[,]silepin (1) with lithium afforded the dilithium salt [(Li)(thf)][12-] (2), which is expected to have antiaromatic character with a pseudo-16π-electron system involving hyperconjugation between the anionic π-clouds and the σ*(Si-Me) orbitals, although the evaluation of its antiaromaticity by NMR was difficult.

Perfluorocycloparaphenylenes.

Perfluorinated aromatic compounds, the so-called perfluoroarenes, are widely used in materials science owing to their high electron affinity and characteristic intermolecular interactions. However, methods to synthesize highly strained perfluoroarenes are limited, which greatly limits their structural diversity. Herein, we report the synthesis and isolation of perfluorocycloparaphenylenes (PFCPPs) as a class of ring-shaped perfluoroarenes.

A new strategy for hyperconjugative antiaromatic compounds utilizing negative charges: a dibenzo[,]silepinyl dianion.

Herein we propose a new strategy for hyperconjugative antiaromatic compounds utilizing negative charges and design the 5,5-diphenyldibenzo[,]silepinyl dianion (pseudo 16π-electron system) in which negative hyperconjugation occurs between the anionic π-cloud and the σ*(Si-Ph) orbital. Essentially, reduction of the dibenzo[,]silepin with lithium readily generated a dilithium salt of the dibenzosilepinyl dianion, and its hyperconjugative antiaromaticity has been evidenced by the upfield shifts of H NMR signals and theoretical calculations, including large NICS values and ACID plots.

Synthesis and structures of diaryloxystannylenes and -plumbylenes embedded in 1,3-diethers of thiacalix[4]arene.

New types of diaryloxystannylenes and -plumbylenes have been synthesized and structurally characterized. Lappert's diaminostannylene and -plumbylene E[N(SiMe3)2]2 (E = Sn, Pb) react with 1,3-diethers of tetrathiacalix[4]arene bearing benzyl or SiiPr3 groups to give the corresponding diaryloxystannylenes and -plumbylenes embedded in thiacalix[4]arene, respectively. X-ray diffraction analysis revealed that these tetrylenes exist as monomers in the solid-state.

P-C reductive elimination in Ru(ii) complexes to convert triarylphosphine ligands into five- or six-membered phosphacycles.

Rare examples of P-C reductive elimination in ruthenium complexes to generate phosphonium salts are presented. Triarylphosphines are converted into benzophospholium or phosphaphenalenium ligands via cyclometalation and 1,2-insertion of an alkyne followed by P-C reductive elimination. The intermediate in each step was successfully characterized using NMR and X-ray diffraction studies.

Reactions of Dilithium Dibenzopentalenides with Cr(CO) (CH CN) : Unexpected Formation of a Cubic Tetramer of an Anionic Hydrodibenzopentalenyl Complex.

To explore the coordination chemistry of dibenzopentalene dianion, reactions of two dilithium dibenzopentalenides having different silyl substituents with Cr(CO) (CH CN) were investigated. The products were unexpected anionic complexes, [Li(Et O)] [Cr(η -9-hydrodibenzopentalenyl)(CO) ] . The proton at the 9-position is derived from Cr(CO) (CH CN) , as evidenced by the use of Cr(CO) (CD CN) .

Synthesis and reactivity of a ruthenocene-type complex bearing an aromatic π-ligand with the heaviest group 14 element.

An anionic ruthenocene derived from a dilithioplumbole complex was prepared. In the complex, the plumbole ligand coordinates a ruthenium atom in an η-fashion, similar to the cyclopentadienyl ligand in ferrocene. The ruthenocene that has the aromatic π-ligand with the heaviest group 14 element reacted with electrophiles to afford the plumbole complexes wherein the plumbole ligands show deviation from planarity, in contrast to the planar plumbole ring in the anionic ruthenocene.

(η(4)-Butadiene)Sn(0) Complexes: A New Approach for Zero-Valent p-Block Elements Utilizing a Butadiene as a 4π-Electron Donor.

Research on zero-valent p-block elements is a recent hot topic in synthetic and theoretical chemistry because of their novel electronic states having two lone pairs in both the s- and p-orbitals. It is considered that σ-donating ligands bearing large substituents are essential to stabilize these species. Herein, we propose a new approach using butadiene as a 4π-electron donor to stabilize zero-valent group 14 elements.

Curved Oligophenylenes as Donors in Shape-Persistent Donor-Acceptor Macrocycles with Solvatofluorochromic Properties.

Many optoelectronic organic materials are based on donor-acceptor (D-A) systems with heteroatom-containing electron donors. Herein, we introduce a new molecular design for all-carbon curved oligoparaphenylenes as donors, which results in the generation of unique shape-persistent D-A macrocycles. Two types of acceptor-inserted cycloparaphenylenes were synthesized.

A reversible two-electron redox system involving a divalent lead species.

Reduction of THF-stabilized plumbacyclopentadienylidene with lithium afforded dilithioplumbole. On the other hand, oxidation of the dilithioplumbole provided the starting plumbacyclopentadienylidene. This is the unprecedented example of a reversible interconversion between group 14 M(II) and its dianionic species bearing organic substituents.

Synthesis, structures, and electronic properties of triple- and double-decker ruthenocenes incorporated by a group 14 metallole dianion ligand.

The neutral triple-decker ruthenocenes and anionic ruthenocene bearing a stannole dianion were successfully synthesized by the reactions of dilithiostannoles with [Cp*RuCl]4. This is the first example of a transition-metal complex bearing a group 14 metallole dianion with μ-η(5):η(5) coordination mode. These complexes were fully characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis.

Facile synthesis of dibenzopentalene dianions and their application as new π-extended ligands.

Reduction of phenyl(silyl)ethynes with potassium followed by quenching with iodine gave dibenzopentalenes in moderate yields. The intermediates of the reactions, dipotassium dibenzopentalenides, were isolated. The first dibenzopentalene-transition-metal complex was successfully synthesized.

Diversity of the structures in a distannene complex and its reduction to generate a six-membered Ti(2)Sn(4) ring complex.

In contrast to olefin complexes, their congeners of heavier elements display various coordination modes, and their complexes may be present as bis(metallylene) complexes, with side-on coordination, as metallacyclopropanes, or as π complexes. In the course of our studies on the reactivity of dilithiostannoles towards transition-metal reagents, three-membered TiSn2 and six-membered Ti2 Sn4 ring complexes were obtained. According to its geometric parameters, NMR analysis, and theoretical calculations, the TiSn2 complex cannot be categorized into any of these previously described bonding modes.

Unexpected formation of Ru2Sn2 bicyclic four-membered ring complexes with butterfly and inverse-sandwich structures.

Reactions of tetraethyldilithiostannole 1 with [Cp*RuCl]4 afforded not η(5)-stannole dianion complexes but two novel bis(stannylene)-bridged dinuclear ruthenium complexes, which have butterfly and inverse-sandwich structures, respectively, depending on the stoichiometry of [Cp*RuCl]4 toward dilithiostannole. The redox behavior between the two complexes is found to be reversible. The molecular structures were determined by X-ray diffraction analysis.

1,1'-Di-tert-butyl-2,2',3,3',4,4',5,5'-octa-ethyl-1,1'-bis-tannole.

The title compound, [Sn(2)(C(4)H(9))(2)(C(12)H(20))(2)], has two 1-stannacyclo-penta-diene skeletons related by inversion symmetry located at the mid-point of the Sn-Sn bond [2.7682 (2) Å]. Thus, the asymmetric unit comprises one half-mol-ecule.