Search

An air-stable B3,N3-containing dibenzobisanthene (8) was prepared in 29% yield by heating a 1,3,5-tri(azasilaanthryl)benzene (5) with BBr3 (180 °C). Under these conditions, the reaction does not stop after threefold SiMe2/BBr exchange but proceeds further via two rearrangement and two intramolecular C–H borylation steps. Some mechanistic details were unveiled by using smaller model systems and applying lower reaction temperatures. According to X-ray crystallography, compound 8 has a helically distorted scaffold. Due to its multiple resonance structure, it shows a narrow-band blue-green emission (λem = 493 nm; ΦPL = 84%; FWHM = 0.20 eV; THF); samples measured in PMMA gave prompt and delayed fluorescence lifetimes of 10.7 ns and 136 μs, respectively. The optical properties of 8 and of structurally related species were also investigated by quantum-chemical means: most of these compounds exhibit a small energy gap ΔEST between the lowest excited singlet (S1) and triplet (T1) states and a non-negligible spin–orbit coupling (SOC) between S1 and T1/T2, demonstrating their potential as thermally activated delayed fluorescence (TADF) emitters. [ABSTRACT FROM AUTHOR]

A joint theoretical and experimental study on 32 endohedral silafullerane derivatives [X@Si20Y20]− (X=F‐I; Y=F‐I, H, Me, Et) and Th ${T_h }$ ‐[Cl@Si20H12Y8]− (Y=F‐I) is presented. First, we evaluated the structure‐determining template effect of Cl− in a systematic series of concave silapolyquinane model systems. Second, we investigated the X−→Si20 interaction energy (Eint ${E_{{\rm{int}}} }$) as a function of X− and Y and found the largest Eint ${E_{{\rm{int}}} }$ values for electron‐withdrawing exohedral substituents Y. Given that X− ions can be considered as Lewis bases and empty Si20Y20 clusters as Lewis acids, we classify our inseparable host–guest complexes [X@Si20Y20]− as "confined Lewis pairs". Third, 35Cl NMR spectroscopy proved to be highly diagnostic for an experimental assessment of the Cl−→Si20 interaction as the paramagnetic shielding and, in turn, δ ${\delta }$ (35Cl) of the endohedral Cl− ion correlate inversely with Eint ${E_{{\rm{int}}} }$. Finally, we disclose the synthesis of [PPN][Cl@Si20Y20] (Y=Me, Et, Br) and provide a thorough characterization of these new silafulleranes. [ABSTRACT FROM AUTHOR]

Despite their apparent simplicity and numerous potential applications, 1,8‐bis(boronic ester) derivatives of naphthalene, 1,8‐C10H6[B(OR)2]2, have remained elusive until today. We now disclose a facile access route to this compound class via alkoholysis of the 1,8‐naphthalenediyl‐bridged diborane(6) 1. In the cases of monotopic MeOH or EtOH, the target compounds 1,8‐C10H6[B(OR)2]2 (R=Me (2), Et (4)) are contaminated with about 10 % of the corresponding mixed boronic ester/anhydride. By using ditopic pinacol (pin) or 1,8‐naphthalenediol (ndl), the formation of the undesired side products is suppressed and 1,8‐C10H6(Bpin)2 (6) can be isolated in 80 % yield (due to solubility issues, the yield of 1,8‐C10H6(Bndl)2 (7) is lower and less reproducible). The bis(boronic ester)s 2, 4, 6, and 7 have been structurally characterized by X‐ray diffraction. 6 has a sterically encumbered, remarkably distorted molecular framework with a torsion angle B−C(ipso)−C'(ipso)−B' of 38.63(9)°. [ABSTRACT FROM AUTHOR]

The thermolysis of Cp′′′Ta(CO)4 with white phosphorus (P4) gives access to [{Cp′′′Ta}2(μ,η2 : 2 : 2 : 2 : 1 : 1‐P8)] (A), representing the first complex containing a cyclooctatetraene‐like (COT) cyclo‐P8 ligand. While ring sizes of n >6 have remained elusive for cyclo‐Pn structural motifs, the choice of the transition metal, co‐ligand and reaction conditions allowed the isolation of A. Reactivity investigations reveal its versatile coordination behaviour as well as its redox properties. Oxidation leads to dimerization to afford [{Cp′′′Ta}4(μ4,η2 : 2 : 2 : 2 : 2 : 2 : 2 : 2 : 1 : 1 : 1 : 1‐P16)][TEF]2 (4, TEF=[Al(OC{CF3}3)4]−). Reduction, however, leads to the fission of one P−P bond in A followed by rapid dimerization to form [K@[2.2.2]cryptand]2[{Cp′′′Ta}4(μ4,η2 : 2 : 2 : 2 : 2 : 2 : 2 : 2 : 1 : 1 : 1 : 1‐P16)] (5), which features an unprecedented chain‐type P16 ligand. Lastly, A serves as a P2 synthon, via ring contraction to the triple‐decker complex [{Cp′′′Ta}2(μ,η6 : 6‐P6)] (B). [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The mixed heteroadamantanes Si6Ge4 and Si6Sn4 are readily accessible from Me2ECl2/Si2Cl6/cat. Cl− (4 × EMe2, 2 × SiCl2, 4 × Si–SiCl3 vertices; E = Ge, Sn). Different from Si6Ge4, two skeletal isomers are formed in the case of Si6Sn4. Site-selective SiCl3-methylation of Si6Ge4 was achieved, leaving the SiCl2 groups untouched. [ABSTRACT FROM AUTHOR]

The Cl− diadduct [nBu4N]2[A·2Cl] of the mixed cyclohexatetrelane (SiCl2)5(GeMe2), A, is accessible from Me2GeCl2, 6 eq. Si2Cl6, and 2 eq. [nBu4N]Cl in one step (96%). Free, tenfold functionalized A can be released from the primary product by decomplexation with AlCl3 (78%). Insight into the assembly mechanism of [nBu4N]2[A·2Cl] and the reactivity of A is provided. [ABSTRACT FROM AUTHOR]

The B‐nucleophilic 9H‐9‐borafluorene dianion reacts with 9‐chloro‐9‐silafluorene to afford air‐ and moisture‐stable silylborate salts M[Ar2(H)B−Si(H)Ar2] (M[HBSiH], M=Li, Na). Li[HBSiH] and Me3SiCl give the B−pyridine adduct Ar2(py)B−Si(H)Ar2 ((py)BSiH) or the chlorosilane Li[Ar2(H)B−Si(Cl)Ar2] (Li[HBSiCl]) in C6H6‐pyridine or THF. In both cases, the first step is H− abstraction at the B center. The resulting free borane subsequently binds a py or thf ligand. While the py adduct is stable at room temperature, the thf adduct undergoes a 1,2‐H shift via the cyclic B(μ‐H)Si intermediate BHSi, which is afterwards attacked at the Si atom by a Cl− ion to give Li[HBSiCl]. DFT calculations were employed to support the proposed reaction mechanism and to characterize the electronic structure of BHSi. Treatment of Li[HBSiCl] with the N‐heterocyclic carbene IMe introduces the neutral donor at the Si atom and leads to Ar2(H)B−Si(IMe)Ar2 (HBSi(IMe)), a donor‐acceptor‐stabilized silylene. [ABSTRACT FROM AUTHOR]

Regioselective di- and tetrabrominations of the (B,O)2-perylene 1 afford derivatives 2–4. Despite their poor solubility, 2 and 4 could be used in Stille-type coupling reactions to introduce two C≡CMe (5) or four C≡C(p-C6H4tBu) substituents (6), respectively. The alkynylated derivatives show blue-green photoluminescence with appreciable quantum efficiencies. [ABSTRACT FROM AUTHOR]

The structures of two new molecular complexes of antimony pentafluoride with pyridine (Py) and acetonitrile (AN), SbF5·Py and Sb2F10·AN, and a molecular complex of antimony trifluoride Sb2F6·Py and its ionic derivative [HPy]+[Sb2F7]− in the solid state have been determined by single crystal X-ray structural analysis. The complexes Sb2F10·AN and Sb2F6·Py are the first structurally characterized compounds of dimeric antimony fluorides. To reveal the nature of bonding in the complexes and their stability, DFT computations of the electronic structure and thermodynamic characteristics were performed, in particular the analysis of the electrostatic potentials, the orbital interactions and the topology. The results indicate that the intermolecular Sb⋯F interactions can be described as a network of pnictogen bonds. [ABSTRACT FROM AUTHOR]

The thermolysis of Cp′′′Ta(CO)4 with white phosphorus (P4) gives access to [{Cp′′′Ta}2(μ,η2 : 2 : 2 : 2 : 1 : 1‐P8)] (A), representing the first complex containing a cyclooctatetraene‐like (COT) cyclo‐P8 ligand. While ring sizes of n >6 have remained elusive for cyclo‐Pn structural motifs, the choice of the transition metal, co‐ligand and reaction conditions allowed the isolation of A. Reactivity investigations reveal its versatile coordination behaviour as well as its redox properties. Oxidation leads to dimerization to afford [{Cp′′′Ta}4(μ4,η2 : 2 : 2 : 2 : 2 : 2 : 2 : 2 : 1 : 1 : 1 : 1‐P16)][TEF]2 (4, TEF=[Al(OC{CF3}3)4]−). Reduction, however, leads to the fission of one P−P bond in A followed by rapid dimerization to form [K@[2.2.2]cryptand]2[{Cp′′′Ta}4(μ4,η2 : 2 : 2 : 2 : 2 : 2 : 2 : 2 : 1 : 1 : 1 : 1‐P16)] (5), which features an unprecedented chain‐type P16 ligand. Lastly, A serves as a P2 synthon, via ring contraction to the triple‐decker complex [{Cp′′′Ta}2(μ,η6 : 6‐P6)] (B). [ABSTRACT FROM AUTHOR]

Die Thermolyse von Cp′′′Ta(CO)4 mit weißem Phosphor (P4) eröffnet den Zugang zu [{Cp′′′Ta}2(μ,η2 : 2 : 2 : 2 : 1 : 1‐P8)] (A), der erste Komplex, der einen cyclooctatetraen‐artigen (COT) cyclo‐P8‐Liganden enthält. Während sich Ringgrößen von n >6 für cyclo‐Pn‐Strukturmotive bisher nicht realisieren ließen, konnte A abhängig von der Wahl des Übergangsmetalls, des Coliganden und der Reaktionsbedingungen isoliert werden. Untersuchungen zur Reaktivität zeigen sein vielseitiges Koordinationsverhalten und seine Redoxeigenschaften. Während die Oxidation zur Dimerisierung führt und [{Cp′′′Ta}4(μ4,η2 : 2 : 2 : 2 : 2 : 2 : 2 : 2 : 1 : 1 : 1 : 1‐P16)][TEF]2 (4, TEF=[Al(OC{CF3}3)4]−) ergibt, führt die Reduktion dagegen zur Spaltung einer P−P‐Bindung in A mit anschließender schneller Dimerisierung und Bildung von [K@[2.2.2]Kryptand]2[{Cp′′′Ta}4(μ4,η2 : 2 : 2 : 2 : 2 : 2 : 2 : 2 : 1 : 1 : 1 : 1‐P16)] (5), welches einen beispiellosen kettenartigen P16‐Liganden aufweist. Letztlich dient A als ein P2‐Synthon, welches über eine Ringkontraktion zum Triple‐Decker‐Komplex [{Cp′′′Ta}2(μ,η6 : 6‐P6)] (B) reagiert. [ABSTRACT FROM AUTHOR]

The mixed heteroadamantanes Si6Ge4 and Si6Sn4 are readily accessible from Me2ECl2/Si2Cl6/cat. Cl− (4 × EMe2, 2 × SiCl2, 4 × Si–SiCl3 vertices; E = Ge, Sn). Different from Si6Ge4, two skeletal isomers are formed in the case of Si6Sn4. Site-selective SiCl3-methylation of Si6Ge4 was achieved, leaving the SiCl2 groups untouched. [ABSTRACT FROM AUTHOR]

Organo(chloro)silanes are essential chemicals, but the synthesis of compounds of the formula RnSiCl4‒n with defined values of n is usually laborious. Herein, we first disclose that a [4+2]-cycloaddition between readily available Cl3SiC≡CSiCl3 and selected dienes provides facile access to vicinal bis(trichlorosilylated) benzenes and bicyclo[2.2.2]octa-2,5-dienes. Second, we show how the number of six Si‒Cl bonds in 1,2-(Cl3Si)2C6H2Me2 (1) can be selectively reduced to four or two by reaction with pinacol (H2pin) or catechol (H2cat), which act as Si···Si'-bridging and/or Si-chelating ligands. Third, we demonstrate that the thermolysis of compound 6, which contains a benzannulated eight-membered C2(SiCl2)2(μ-pin) ring with Si···Si'-bridging pin moiety, furnishes 13 with a benzannulated five-membered C2(SiCl2)2O ring via the release of pinacolone. Such cyclic disiloxanes are valuable building blocks for specialty silicones; an alternative assembly of the Si‒O‒Si unit by controlled hydrolysis of 1 is not feasible if the four valuable Si‒Cl functionalities are to be retained for further derivatization. Substitution of one Cl atom per Si site of 13 gives the rac-1,3-disila-2-oxaindane rac-15 with high selectivity., (© 2024 Wiley‐VCH GmbH.)

An air-stable B 3 ,N 3 -containing dibenzobisanthene (8) was prepared in 29% yield by heating a 1,3,5-tri(azasilaanthryl)benzene (5) with BBr 3 (180 °C). Under these conditions, the reaction does not stop after threefold SiMe 2 /BBr exchange but proceeds further via two rearrangement and two intramolecular C-H borylation steps. Some mechanistic details were unveiled by using smaller model systems and applying lower reaction temperatures. According to X-ray crystallography, compound 8 has a helically distorted scaffold. Due to its multiple resonance structure, it shows a narrow-band blue-green emission ( λ em = 493 nm; Φ PL = 84%; FWHM = 0.20 eV; THF); samples measured in PMMA gave prompt and delayed fluorescence lifetimes of 10.7 ns and 136 μs, respectively. The optical properties of 8 and of structurally related species were also investigated by quantum-chemical means: most of these compounds exhibit a small energy gap Δ E ST between the lowest excited singlet (S 1 ) and triplet (T 1 ) states and a non-negligible spin-orbit coupling (SOC) between S 1 and T 1 /T 2 , demonstrating their potential as thermally activated delayed fluorescence (TADF) emitters.

Two (BE) 8 -[16]annulenes were prepared and fully characterized by experimental and quantum-chemical means ( 1 , E = N; 2 , E = O). The 1,8-naphthalenediyl-bridged diborane(6) 3 served as their common starting material, which was treated with [Al(NH 3 ) 6 ]Cl 3 to form 1 (91% yield) or with 1,8-naphthalenediboronic acid anhydride to form 2 (93% yield). As a result, the heteroannulenes 1 and 2 are supported by four aromatic "clamps" and may also be viewed as NH- or O-bridged cyclic tetramers of BNB- or BOB-doped phenalenyls. X-ray crystallography on mono-, di-, and tetraadducts 2 ·thf, 2 ·py 2 , and 2 ·py 4 showed that 2 is an oligotopic Lewis acid (thf/py: tetrahydrofuran/pyridine donor). The applicability of 2 also as a Lewis basic ligand in coordination chemistry was demonstrated by the synthesis of the mononuclear Ag + complex [Ag(py) 2 ( 2 ·py 4 )] + and the dinuclear Pb 2+ complex 6 . During the assembly of 6 , the rearrangement of 2 led to the formation of two (BO) 9 -macrocycles linked by two BOB-phenalenyls to form a nanometer-sized cage with four negatively charged, tetracoordinated B atoms. Both 1 and 2 show several redox waves in the cathodic regions of the cyclic voltammograms. An in-depth assessment of the consequences of electron injection on the aromaticity of 1 and 2 was achieved by electronic structure calculations. 1 and 2 are proposed to exhibit aromatic switching capabilities in the [16]annulene motif.

An air-stable B 3 ,N 2 -PAH ( B 3 N 2 ; nine annulated six-membered rings) was synthesized from 1-X-2,6-di(azasilaanthryl)benzenes (X = Cl, I) via lithiation/borylation, electrophilic aromatic borylation, and Si/B exchange. The heteroatom distribution in B 3 N 2 meets the requirements for multiple resonance thermally activated delayed fluorescence (MR-TADF). Indeed, B 3 N 2 emits green light (λ em = 523 nm; Φ PL = 85%; CHCl 3 ) with a small fwhm of 0.15 eV. Lifetimes for prompt (7.8 ns) and delayed (60 μs) fluorescence were measured in PMMA.

The B 2 ,N 4 -doped heptacene H4 in which two N , N '-dihydrophenazine units are linked by two BMes bridges (Mes = mesityl) was synthesized via fourfold Buchwald-Hartwig coupling between 2,3,6,7-tetrachloro-9,10-dimesityl-9,10-dihydro-9,10-diboraanthracene and o -phenylenediamine ( t BuXPhos-Pd-G3, DBU/NaOTf, 2-MeTHF, 50 °C, 16 h). Upon exposure to ambient air, H4 is oxidized to its N , N '-dihydro form H2 ; further oxidation with MnO 2 furnishes the di(phenazine) derivative H0 . Stirring under a blanket of H 2 in the presence of Pd/C hydrogenates H0 back to H2 and ultimately H4 . Yellow-colored H0 is a remarkably good electron acceptor with a LUMO-energy level of -3.9 eV; upon irradiation with a 405 nm LED in the presence of THF or 1,4-cyclohexadiene, H0 accepts two H atoms to furnish H2 . One-electron reduction of H0 yields the isolable radical-anion salt Li[ H0 ] (lithium naphthalenide, THF, -30 °C to rt). The ambipolar compounds H2 and H4 possess a navy blue and deep purple color, respectively, due to charge-transfer interactions from the electron-rich N , N '-dihydrophenazine donor(s) to the electron-accepting B 2 C 4 core.