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The tetraaryl μ‐hydridodiborane(4) anion [2H]− possesses nucleophilic B−B and B−H bonds. Treatment of K[2H] with the electrophilic 9‐H‐9‐borafluorene (HBFlu) furnishes the B3 cluster K[3], with a triangular boron core linked through two BHB two‐electron, three‐center bonds and one electron‐precise B−B bond, reminiscent of the prominent [B3H8]− anion. Upon heating or prolonged stirring at room temperature, K[3] rearranges to a slightly more stable isomer K[3 a]. The reaction of M[2H] (M+=Li+, K+) with MeI or Me3SiCl leads to equimolar amounts of 9‐R‐9‐borafluorene and HBFlu (R=Me or Me3Si). Thus, [2H]− behaves as a masked [:BFlu]− nucleophile. The HBFlu by‐product was used in situ to establish a tandem substitution‐hydroboration reaction: a 1:1 mixture of M[2H] and allyl bromide gave the 1,3‐propylene‐linked ditopic 9‐borafluorene 5 as sole product. M[2H] also participates in unprecedented [4+1] cycloadditions with dienes to furnish dialkyl diaryl spiroborates, M[R2BFlu].
The title compound, [Li3(C4F9O)3(C3H6O)3], features an open Li/O cube with an Li ion missing at one corner. Three of the four bridging O atoms of the cube carry a fluorinated tert-butyl residue, whereas the fourth is part of an acetone molecule. Two of the Li atoms are further bonded to a non-bridging acetone molecule. Two of the lithium ion coordination geometries are very distorted LiO4 tetrahedra; the third could be described as a very distorted LiO3 T-shape with two distant F-atom neighbours. The Li[cdots, three dots, centered]Li contact distances for the three-coordinate Li+ ion [2.608 (14) and 2.631 (12) Å] are much shorter that the contact distance [2.940 (13) Å] between the tetrahedrally coordinated species.
The crystal structure of the title compound, Na[(C6F5)BH3], is composed of discrete anions and cations. The sodium cations are surrounded by four anions with three short Na...B [2.848 (8), 2.842 (7) and 2.868 (8) Å] and two short Na...F contacts [2.348 (5) and 2.392 (5) Å], forming a three-dimensional network. The anion is the first structural example of a pentafluorophenyl ring carrying a BH3 group.
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.
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.
SixGey alloys are emerging materials for modern semiconductor technology. Well-defined model systems of the bulk structures aid in understanding their intrinsic characteristics. Three such model clusters have now been realized in the form of the SixGey heteroadamantanes [0], [1], and [2] through selective one-pot syntheses starting from Me2GeCl2, Si2Cl6, and [nBu4N]Cl. Compound [0] contains six GeMe2 and four SiSiCl3 vertices, whereas one and two of the GeMe2 groups are replaced by SiCl2 moieties in compounds [1] and [2], respectively. Chloride-ion-mediated rearrangement quantitatively converts [2] into [1] at room temperature and finally into [0] at 60 °C, which is not only remarkable in view of the rigidity of these cage structures but also sheds light on the assembly mechanism.
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.
The crystal structure of the title salt, [Li(CH3CN)4][B(NCS)4], is composed of discrete cations and anions. Both the Li and B atoms show a tetrahedral coordination by four equal ligands. The acetonitrile and isothiocyanate ligands are linear. The bond angles at the B atom are close to the ideal tetrahedral value [108.92 (18)–109.94 (16)°], but the bond angles at the Li atom show larger deviations [106.15 (17)–113.70 (17)°].
The crystal structure of the title compound, hexa-μ2-bromido-μ4-oxido-tetrakis[(diethyl ether)magnesium], [Mg4Br6O(C4H10O)4], determined from data measured at 173 K, differs from the previously known structure of diethyl ether magnesium oxybromide, which was determined from room-temperature data [Stucky & Rundle (1964 [triangle]). J. Am. Chem. Soc. 86, 4821–4825]. The title compound crystallizes in the tetragonal space group I An external file that holds a picture, illustration, etc. Object name is e-67-m1614-efi7.jpg, whereas the previously known structure crystallizes in a different tetragonal space group, namely P An external file that holds a picture, illustration, etc. Object name is e-67-m1614-efi7.jpg21 c. Both molecules have crystallographic An external file that holds a picture, illustration, etc. Object name is e-67-m1614-efi7.jpg symmetry and show almost identical geometric parameters for the Mg, Br and O atoms. The crystal of the title compound turned out to be a merohedral twin emulating a structure with apparent Laue symmetry 4/mmm, whereas the correct Laue group is just 4/m. The fractional contribution of the minor twin component converged to 0.462 (1).
Two subvalent, redox-active diborane(4) anions, [3]4− and [3]2−, carrying exceptionally high negative charge densities are reported: Reduction of 9-methoxy-9-borafluorene with Li granules without stirring leads to the crystallization of the B(sp3)−B(sp2) diborane(5) anion salt Li[5]. [5]− contains a 2,2′-biphenyldiyl-bridged B−B core, a chelating 2,2′-biphenyldiyl moiety, and a MeO substituent. Reduction of Li[5] with Na metal gives the Na+ salt of the tetraanion [3]4− in which two doubly reduced 9-borafluorenyl fragments are linked via a B−B single bond. Comproportionation of Li[5] and Na4[3] quantitatively furnishes the diborane(4) dianion salt Na2[3], the doubly boron-doped congener of 9,9′-bis(fluorenylidene). Under acid catalysis, Na2[3] undergoes a formal Stone–Wales rearrangement to yield a dibenzo[g,p]chrysene derivative with B=B core. Na2[3] shows boron-centered nucleophilicity toward n-butyl chloride. Na4[3] produces bright blue chemiluminescence when exposed to air.