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ansa-Ferrocenes with pyrazahole bridges are chemically robust entities and therefore suitable building blocks for the synthesis of rigid-rod polymers that combine redox-active Fe(II) centers and beltene-like [pi] faces. The specific monomers we developed bear OEt groups at both tetracoordinated boron atoms (for solubility reasons) and ethynyl substituents at the 4-positions of the two pyrazole rings. Polymerization was accomplished by a condensation reaction with 1,4-diiodobenzene using a Sonogashira-Hagihara-type protocol. As a result, oligomers with a number-average molecular weight of [M.sub.n] = 7.6 kDa and dispersity of D= 1.55 were obtained, suggesting an average chain length of about 14 repeating units based on gel permeation chromatography analysis in THF relative to narrow polystyrene standards. The molecular weight determination was complemented by MALDI-TOF mass spectrometry and (heteronuclear) NMR spectroscopy to verify the intact pyrazabole monomer repeat units and the nature of the end groups. The oligomers were further characterized by UV-vis spectroscopy and cyclic voltammetry which demonstrated the successful synthesis of a new class of redox-active materials. Key words: boron, ferrocene, organometallic polymer, pyrazabole Les ansa-ferrocènes avec ponts pyrazabole sont des entités chimiquement robustes et peuvent donc servir d'unités de base pour la synthèse de polymères à tiges rigides qui comportent à la fois des atomes centraux de Fe(II) présentant une activité rédox et des faces [pi] de type beltène. Les monomères précis que nous avons mis au point portent des groupes OEt sur les deux atomes de bore tétracoordonnés (pour des raisons de solubilité) et des substituants éthynyles en position 4 des deux cycles pyrazole. Nous avons réalisé la polymérisation par condensation avec le 1,4-diiodobenzène en utilisant une méthode de type Sonogashira-Hagihara. Nous avons ainsi obtenu des oligomères dont le poids moléculaire moyen [M.sub.n] est de 7,6 kDa et l'indice de dispersité D, de 1,55, et dont la longueur moyenne des chaînes est d'environ 14 unités répétitives d'après la comparaison par chromatographie sur gel perméable (GPC) dans le THF à des étalons de polystyrène à intervalles étroits de longueur de chaîne. Nous avons déterminé le poids moléculaire par spectrométrie de masse MALDI-TOF et confirmé la présence des unités répétitives intactes du monomère pyrazabole ainsi que la nature des groupes terminaux par spectroscopic RMN (hétéroonucléaire). Les oligomères ont été caractérisés par spectroscopic UV-visible et voltampérométrie cyclique, ce qui a permis de confirmer la synthèse d'une nouvelle classe de matériaux présentant une activité rédox. [Traduit par la Rédaction] Mots-clés : bore, ferrocéne, polymère organométallique, pyrazabole, Introduction Organometallic macromolecules are a class of materials that often possess useful optical, electronic, and magnetic properties. (1) Ferrocene is a particularly valuable building block in this context as it [...]

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 title compound, di-μ3-chlorido-tetra-μ2-chlorido-tetrakis(diethyl ether-κO)bis(1,1-dimethylethyl)tetramagnesium, [Mg4(C4H9)2Cl6(C4H10O)4], features an Mg4Cl6 open-cube cluster. The two four-coordinate Mg2+ ions show an almost tetrahedral coordination, whereas the two six-coordinate Mg2+ ions have their ligands in an octahedral environment. The Mg--Cl bond lengths differ depending on the coordination number (2 or 3) of the bridging μ-Cl- ligands. There are few comparable structures deposited in the Cambridge Structural Database. [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]

Helicenes combine two central themes in chemistry: extended π‐conjugation and chirality. Hetero‐atom doping preserves both characteristics and allows modulation of the electronic structure of a helicene. Herein, we report the (BO)2‐doped tetrathia[7]helicene 1, which was prepared from 2‐methoxy‐3,3′‐bithiophene in four steps. 1 is formally derived by substituting two (Mes)B−O moieties in place of (H)C=C(H) fragments in two benzene rings of the parent tetrathia[7]helicene. X‐ray crystallography revealed a dihedral angle of 50.26(9)° between the two terminal thiophene rings. The (P)‐/(M)‐1 enantiomers were separated by chiral HPLC and are configurationally stable at room temperature. The experimentally determined enantiomerization barrier of 27.4±0.1 kcal mol−1 is lower than that of tetrathia[7]helicene (39.4±0.1 kcal mol−1). The circular dichroism spectra of (P)‐ and (M)‐1 show a perfect mirror‐image relationship. 1 is a blue emitter (λem=411 nm) with a photoluminescence quantum efficiency of ΦPL=6 % (cf. tetrathia[7]helicene: λem≈405 nm, ΦPL=5 %). [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]