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Vicinally diiodinated polycyclic aromatic hydrocarbons (I2‐PAHs) are accessible from the corresponding diborylated B2‐PAHs through boron/iodine exchange. The B2‐PAHs have been prepared via twofold electrophilic borylation reactions templated by a vicinally disilylated benzene. Our protocol is applicable to fluorenes, acenes, annulated acenes, oligoaryls, and even [5]helicene. Using B2‐naphthalene as the example, we have shown that the reaction scope can, in principle, be expanded to include the synthesis of vicinally dibrominated and dihydroxylated PAHs. The usefulness of the building blocks provided by our method in the field of optoelectronic materials was demonstrated by the successful conversion of I2‐fluoranthene to the analogous doubly alkynylated fluoranthene emitter.
[1,3-Bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene]triiodoborane benzene hemisolvate
(2020)
Two salts of the 6,6-difluoro-6H-dibenzo[c,e][1,2]oxaborinin-6-ide anion with different cations
(2020)
The crystal structures are reported of the 6,6-difluoro-6H-dibenzo[c,e][1,2]oxaborinin-6-ide (or 9,9-difluoro-10-oxa-9-boraphenanthren-9-ide) anion with two different cations, namely, potassium 6,6-difluoro-6H-dibenzo[c,e][1,2]oxaborinin-6-ide, K+·C12H8BF2O−, (II), featuring a polymeric structure, and bis(tetraphenylphosphonium) bis(6,6-difluoro-6H-dibenzo[c,e][1,2]oxaborinin-6-ide) acetonitrile trisolvate, 2C24H20P+·2C12H8BF2O−·3CH3CN, (III), which is composed of discrete cations, anions and acetonitrile solvent molecules linked by C—H...O, C—H...N and C—H...F hydrogen bonds. There are only minor differences in the geometrical parameters of the anions in these structures.
We have encountered two polymorphs of the title compound, C24H16B2OS2, both of which display almost the same unit-cell parameters. Compound (I) crystallizes in the non-centrosymmetric space group P21 with four molecules in the asymmetric unit. These molecules are related by pseudosymmetry. As a result, the space group looks like P21/c, but the structure cannot be refined successfully in that space group. Compound (II) on the other hand crystallizes in the centrosymmetric space group P21/c with only two molecules in the asymmetric unit. The crystals studied for (I) and (II) were both non-merohedral twins.
Iodo(triphenyl)silane
(2019)
The molecular structure of the title compound, C18H15ISi, which crystallizes in the space group C2/c, does not exhibit any unusual features. Two weak C—H⋯π interactions may help to consolidate the packing. The present structure is not isostructural with the known Ph3SiX (X = F, Cl or Br) compounds.
Double reduction of the THF adduct of 9H-9-borafluorene (1⋅THF) with excess alkali metal affords the dianion salts M2[1] in essentially quantitative yields (M=Li–K). Even though the added charge is stabilized through π delocalization, [1]2− acts as a formal boron nucleophile toward organoboron (1⋅THF) and tetrel halide electrophiles (MeCl, Et3SiCl, Me3SnCl) to form B−B/C/Si/Sn bonds. The substrate dependence of open-shell versus closed-shell pathways has been investigated.
Organoboranes are among the most versatile and widely used reagents in synthetic chemistry. A significant further expansion of their application spectrum would be achievable if boron-containing reactive intermediates capable of inserting into C–H bonds or performing nucleophilic substitution reactions were readily available. However, current progress in the field is still hampered by a lack of universal design concepts and mechanistic understanding. Herein we report that the doubly arylene-bridged diborane(6) 1H2 and its B[double bond, length as m-dash]B-bonded formal deprotonation product Li2[1] can activate the particularly inert C(sp3)–H bonds of added H3CLi and H3CCl, respectively. The first case involves the attack of [H3C]− on a Lewis-acidic boron center, whereas the second case follows a polarity-inverted pathway with nucleophilic attack of the B[double bond, length as m-dash]B double bond on H3CCl. Mechanistic details were elucidated by means of deuterium-labeled reagents, a radical clock, α,ω-dihaloalkane substrates, the experimental identification of key intermediates, and quantum-chemical calculations. It turned out that both systems, H3CLi/1H2 and H3CCl/Li2[1], ultimately funnel into the same reaction pathway, which likely proceeds past a borylene-type intermediate and requires the cooperative interaction of both boron atoms.
We have determined the crystal structures of two decachlorocyclopentasilanes, namely bis(tetra-n-butylammonium) dichloride decachlorocyclopentasilane dichloromethane disolvate, 2C16H36N+·2Cl−·Si5Cl10·2CH2Cl2, (I), and bis(tetraethylammonium) dichloride decachlorocyclopentasilane dichloromethane disolvate, 2C8H20N+·2Cl−·Si5Cl10·2CH2Cl2, (II), both of which crystallize with discrete cations, anions, and solvent molecules. In (I), the complete decachlorocyclopentasilane ring is generated by a crystallographic twofold rotation axis. In (II), one cation is located on a general position and the other two are disordered about centres of inversion. These are the first structures featuring the structural motif of a five-membered cyclopentasilane ring coordinated from both sides by a chloride ion. The extended structures of (I) and (II) feature numerous C—H⋯Cl interactions. In (II), the N atoms are located on centres of inversion and as a result, the ethylene chains are disordered over equally occupied orientations.
The geminal frustrated Lewis pair tBu2PCH2B(Fxyl)2 (1; Fxyl=3,5-(CF3)2C6H3) is accessible in 65 % yield from tBu2PCH2Li and (Fxyl)2BF. According to NMR spectroscopy and X-ray crystallography, 1 is monomeric both in solution and in the solid state. The intramolecular P⋅⋅⋅B distance of 2.900(5) Å and the full planarity of the borane site exclude any significant P/B interaction. Compound 1 readily activates a broad variety of substrates including H2, EtMe2SiH, CO2/CS2, Ph2CO, and H3CCN. Terminal alkynes react with heterolysis of the C−H bond. Haloboranes give cyclic adducts with strong P−BX3 and weak R3B−X bonds. Unprecedented transformations leading to zwitterionic XP/BCX3 adducts occur on treatment of 1 with CCl4 or CBr4 in Et2O. In less polar solvents (C6H6, n-pentane), XP/BCX3 adduct formation is accompanied by the generation of significant amounts of XP/BX adducts. FLP 1 catalyzes the hydrogenation of PhCH=NtBu and the hydrosilylation of Ph2CO with EtMe2SiH.
In the title salt, [Ag(C27H36N2)2]Cl·C4H8O, the AgI atom is coordinated by two 1,3-bis(2,6-dimethylphenyl)imidazol-2-ylidene ligands. The imidazole rings are inclined to one another by 46.69 (13)° and the benzene rings in each ligand are almost normal to the imdazole ring to which they are attached, with dihedral angles varying from 82.39 (13) to 88.27 (12)°. There are C—H⋯π interactions present in the cation, involving the two ligands, and the solvent molecule is linked to the cation via a C—H⋯O hydrogen bond. In the crystal, molecules are linked by trifurcated C—H⋯(Cl,Cl,Cl) hydrogen bonds, forming slabs parallel to (101). One isopropyl group is disordered over two sets of sites with an occupancy ratio of 0.447 (17):0.553 (17) and the THF molecule is disordered over two positions with an occupancy ratio of 0.589 (6):0.411 (6).