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ABSTRACT: Finally, boron did it too: The first example of a dimeric organyl(hydro)borane with a B-B-bridging aryl ring has been elucidated (see picture; B green/blue, C black/gray). It features a B-C-B two-electron-three-center bond and a largely unperturbed aromatic π-electron system.
Angewandte Chemie International Edition 11/2012; · 13.45 Impact Factor
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ABSTRACT: The crystal structure of the title compound, Na[(C(6)F(5))BH(3)], 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 BH(3) group.
Acta Crystallographica Section E Structure Reports Online 11/2012; 68(Pt 11):m1371. · 0.35 Impact Factor
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ABSTRACT: The reaction of 9,10-dibromo-9,10-dihydro-9,10-diboraanthracene (9,10-dibromo-DBA, 3) with two equivalents of 9-lithio-2,6- or 9-lithio-2,7-di-tert-butylanthracene gave the corresponding 9,10-dianthryl-DBAs featuring two (4) or four (5) inward-pointing tert-butyl groups. Compound 4 exists as two atropisomers, 4 and 4', due to hindered rotation about the exocyclic BC bonds. X-ray crystallography of 5 suggests that the overall interactions between facing tert-butyl groups are attractive rather than repulsive. Even in solution, 4/4' and 5 are stable toward air and moisture for several hours. Treatment of 3 with 10-lithio-9-R-2,7-di-tert-butylanthracenes carrying phenyl (R=Ph), dimesitylboryl (R=Mes(2) B), or N,N-di(p-tolyl)amino (R=Tol(2) N) groups gave the corresponding 9,10-dianthryl-DBA derivatives 9-11 in moderate to good yields. In these molecules, all four solubilizing tert-butyl groups are outward pointing. The solid-state structures of 4, 5, 9, and 10 reveal twisted conformations about the exocyclic BC bonds with dihedral angles of 70-90°. A significant electron-withdrawing character was proven for the Mes(2) B moiety, but no appreciable +M effect was evident for Tol(2) N. Compounds 5, 9, and 11 show two reversible DBA-centered reduction waves in the cyclic voltammogram. In the case of 10, a third reversible redox transition can be assigned to the Mes(2) B-anthryl substituents. The UV/Vis absorption spectrum of 5 is characterized by a very broad band at λ(max) =510 nm, attributable to a twisted intramolecular charge-transfer interaction from the anthryl donors to the DBA acceptor. The corresponding emission band shows pronounced positive solvatochromism (λ(em) =567 nm, C(6) H(12) ; 680 nm, CH(2) Cl(2) ) in line with a highly polar excited state. The charge-transfer bands of 10 and 11, as well as the emission bands of 9 and 10, are redshifted relative to those of 5. The Tol(2) N derivative 11 is essentially nonfluorescent in solution, but emits bright wine-red light in the solid state.
Chemistry 10/2012; · 5.93 Impact Factor
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ABSTRACT: The reaction of [Cp(2)ZrCl(2)] with the lithium salt Li[FcBH(3)] in stoichiometric ratios of 1.5 : 1 or 0.4 : 1 furnishes the mixed-metallocene complexes [Cp(2)(Cl)Zr(H(3)BFc)] () and [Cp(2)Zr(H(3)BFc)(2)] (), respectively (Cp = cyclopentadienyl; Fc = ferrocenyl). When the two reagents are combined in a ratio of 0.6 : 1, complex is formed together with the zirconium hydride species [Cp(2)(H)Zr(H(3)BFc)] (). Compound can be obtained in pure form from [Cp(2)Zr(H)Cl] and Li[FcBH(3)]. Treatment of the half-sandwich complexes [(C(5)R(5))ZrCl(3)] with 3 equivalents of Li[FcBH(3)] leads to the heterotetranuclear aggregates [(C(5)R(5))Zr(H(3)BFc)(3)] (: R = H; : R = CH(3)). Li(2)[fc(BH(3))(2)] and 3 equivalents of [Cp(2)ZrCl(2)] give the heterotrinuclear compound [fc(BH(3)Zr(Cl)Cp(2))(2)] () with bridging ferrocenylene core (fc = 1,1'-ferrocenylene). According to X-ray crystallography, the trihydroborate ions are coordinated in a [Zr(μ-H)(2)B(H)-] fashion in , , and , whereas and are carrying tridentate trihydroborate ligands.
Dalton Transactions 09/2012; · 3.84 Impact Factor
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ABSTRACT: 1,2-Bis(pinacolboryl)benzene (1,2-C(6)H(4) (Bpin)(2), 2) was synthesized in preparatively useful yields from 1,2-C(6)H(4)Br(2), iPrO-Bpin, and Mg turnings in the presence of 1,2-C(2)H(4)Br(2) as an entrainer. Compound 2 is a versatile starting material for the synthesis of (un)symmetrically substituted benzenes (i.e., 1,2-C(6)H(4)(Ar(1))(Ar(2))) through sequential Suzuki-Miyaura coupling reactions. Alternatively, it can be transformed into bis-borate Li(2)[1,2-C(6)H(4)(BH(3))(2)] (3) through reduction with Li[AlH(4)]. In the crystal lattice, the diethyl ether solvate 3·OEt(2) establishes a columnar structure that is reinforced by an intricate network of B-(μ-H)-Li interactions. Hydride-abstraction from compound 3 with Me(3)SiCl leads to the transient ditopic borane 1,2-C(6)H(4)(BH(2))(2), which can either be used in situ for subsequent hydroboration reactions or trapped as its stable NMe(2)Et diadduct (6). In SMe(2) solution, the putative diadduct 1,2-C(6)H(4)(BH(2)·SMe(2))(2) is not long-term stable but rather undergoes a condensation reaction to give 9,10-dihydro-9,10-diboraanthracene, HB(μ-C(6)H(4))(2)BH, and BH(3). 9,10-Dihydro-9,10-diboraanthracene was isolated from the reaction mixture as its SMe(2) monoadduct (7), which dimerizes in the solid state through two B-H-B bridges ((7)(2), elucidated by X-ray crystallography). In contrast, hydride-abstraction from compound 3 in THF or CH(2)Cl(2) provides the unique exo-adduct H(2)B(μ-H)(2)B(μ-C(6)H(4))(2)B(μ-H)(2)BH(2) (8, elucidated by X-ray crystallography). Quantum-chemical calculations on various conceivable isomers of [1,2-C(6)H(4)(BH(2))(2)](2) revealed that compound 8 was the most stable of these species. Moreover, the calculations confirmed the experimental findings that the NMe(2)Et diadduct of 1,2-C(6)H(4)(BH(2))(2) is significantly more stable than the corresponding SMe(2) complex and that the latter complex is not able to compete successfully with borane-dimerization and -condensation. The reaction cascade in SMe(2), which proceeds from 1,2-C(6)H(4)(BH(2))(2) to the observed adducts of HB(μ-C(6)H(4))(2)BH, has been elucidated in detail and the important role of B-C-B-bridged intermediates has been firmly established.
Chemistry 07/2012; 18(36):11284-95. · 5.93 Impact Factor
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ABSTRACT: The addition compound Cl(3)SiSiCl(3)·TMEDA was formed quantitatively by treatment of Cl(3)SiSiCl(3) with tetramethylethylenediamine (TMEDA) in pentane at room temperature. The crystal structure of Cl(3)SiSiCl(3)·TMEDA displays one tetrahedrally and one octahedrally bonded Si atom (monoclinic, P2(1)/n). (29)Si CP/MAS NMR spectroscopy confirms this structure. Density functional theory (DFT) calculations have shown that the structure of the meridional isomer of Cl(3)SiSiCl(3)·TMEDA is 6.3 kcal lower in energy than that of facial coordinate species. Dissolving of Cl(3)SiSiCl(3)·TMEDA in CH(2)Cl(2) resulted in an immediate reaction by which oligochlorosilanes Si(n)Cl(2n) (n = 4, 6, 8, 10; precipitate) and the Cl(-)-complexed dianions [Si(n)Cl(2n+2)](2-) (n = 6, 8, 10, 12; CH(2)Cl(2) extract) were formed. The constitutions of these compounds were confirmed by MALDI mass spectrometry. Additionally, single crystals of [Me(3)NCH(2)CH(2)NMe(2)](2)[Si(6)Cl(14)] and [Me(3)NCH(2)CH(2)NMe(2)](2)[Si(8)Cl(18)] were obtained from the CH(2)Cl(2) extract. We found that Cl(3)SiSiCl(3)·TMEDA reacts with MeCl, forming MeSiCl(3) and the products that had been formed in the reaction of Cl(3)SiSiCl(3)·TMEDA with CH(2)Cl(2). X-ray structure analysis indicates that the structures of [Me(3)NCH(2)CH(2)NMe(2)](2)[Si(6)Cl(14)] (monoclinic, P2(1)/n) and [Me(3)NCH(2)CH(2)NMe(2)](2)[Si(8)Cl(18)] (monoclinic, P2(1)/n) contain dianions adopting an "inverse sandwich" structure with inverse polarity and [Me(3)NCH(2)CH(2)NMe(2)](+) as countercations. Single crystals of SiCl(4)·TMEDA (monoclinic, Cc) could be isolated by thermolysis reaction of Cl(3)SiSiCl(3)·TMEDA (50 °C) in tetrahydrofuran (THF).
Inorganic Chemistry 07/2012; 51(15):8599-606. · 4.60 Impact Factor
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ABSTRACT: The crystal structure of the title compound, [Fe(C(5)H(5))(CH(3)CN)(CO)(2)]BF(4), of which only the coordinates of the non-H atoms of the cation have previously been reported [Fadel et al. (1979 ▶). Z. Anorg. Allg. Chem.453, 98-106] has been redetermined. The Fe(II) atom in the complex cation is coordinated by a cyclo-penta-dienyl ring, two carbonyl ligands and an acetonitrile mol-ecule displaying a three-legged piano stool structure. Three of the four F atoms of the BF(4) (-) anion are disordered over two sets of sites, with a site-occupancy factor of 0.709 (10) for the major occupied site.
Acta Crystallographica Section E Structure Reports Online 07/2012; 68(Pt 7):m966. · 0.35 Impact Factor
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ABSTRACT: A new polymorph of the title compound, [Pd(2)(C(8)H(18)P)(2)(C(8)H(19)P)(2)], has been found. It belongs to the triclinic P-1 space group, whereas the known form [Leoni, Sommovigo, Pasquali, Sabatino & Braga (1992 ▶), J. Organo-met. Chem.423, 263-270] crystallizes in the monoclinic C2/c space group. The title compound features a dinuclear palladium complex with a planar central Pd(2)(μ-P)(2) core (r.m.s. deviation = 0.003 Å). The Pd-Pd distance of 2.5988 (5) Å is within the range of a Pd(I)-Pd(I) bond. The mol-ecules of both polymorphs are located on a crystallographic centre of inversion. The mol-ecular conformations of the two polymorphs are essentially identical. The crystal packing patterns, on the other hand, are slightly different.
Acta Crystallographica Section E Structure Reports Online 06/2012; 68(Pt 6):m836. · 0.35 Impact Factor
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ABSTRACT: In the title compound, C(27)H(37)N(2) (+)·Cl(-)·2CH(2)Cl(2), the cation and the anion are each located on a crystallographic mirror plane. Both of the dichloro-methane solvent mol-ecules show a disorder across a mirror plane over two equally occupied positions. Additionally, one isopropyl group is also disordered. In the crystal, the cations are connected to the chloride ions via C-H⋯Cl hydrogen bonds.
Acta Crystallographica Section E Structure Reports Online 06/2012; 68(Pt 6):o1844. · 0.35 Impact Factor
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ABSTRACT: In the title compound, C(27)H(37)N(2) (+)·Br(-)·2CH(2)Cl(2), both the cation and the anion are located on a crystallographic mirror plane. Both of the dichloro-methane solvent mol-ecules show a disorder across a mirror plane over two equally occupied positions. In the crystal, the cations are connnected to the bromide ions via C-H⋯Br hydrogen bonds.
Acta Crystallographica Section E Structure Reports Online 06/2012; 68(Pt 6):o1845. · 0.35 Impact Factor
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ABSTRACT: The crystal structures of five dibromobenzene derivatives, namely dibromoborylbenzene, C(6)H(5)BBr(2), (I), 1-dibromoboryl-4-(trimethylsilyl)benzene, C(9)H(13)BBr(2)Si, (II), 4-bromo-1-(dibromoboryl)benzene, C(6)H(4)BBr(3), (III), dibromo(dimethylamino)(phenyl)borane, C(8)H(12)BBr(2)N, (IV), and dibromo(dimethylsulfanyl)[4-(trimethylsilyl)phenyl]borane, C(11)H(19)BBr(2)SSi, (V), have been determined. Compounds (I)-(IV) crystallize with one molecule in the asymmetric unit, but the molecule of (V) is located on a crystallographic mirror plane, implying twofold disorder of the central aromatic ring, the S atom and one of the methyl groups bonded to the S atom. In (I), (II) and (III), the B atom is three-coordinated, and in (IV) and (V) it is four-coordinated. The geometric parameters of the -BBr(2) group in these five structures agree well with those of comparable structures retrieved from the Cambridge Structural Database. The C-B and B-Br bond lengths in the molecules with a three-coordinated B atom are significantly shorter than those in the molecules with a four-coordinated B atom. In the compounds with a three-coordinated B atom, the -BBr(2) group tends to be coplanar with the aromatic ring to which it is attached.
Acta crystallographica. Section C, Crystal structure communications 06/2012; 68(Pt 6):o226-30. · 0.78 Impact Factor
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ABSTRACT: A highly efficient route for the synthesis of valuable 3,4-substituted chromenone derivatives by the reaction of 1,3-diketones with aldehydes in the presence of l-proline was developed. The reactions take advantage of readily available starting materials and follow a Knoevenagel condensation/Michael addition/hemiacetalization domino process. Chiral 3-substituted chromenones are obtained with high enantioselectivities when a chiral diarylprolinol TMS-ether is applied in the reaction.
Organic & Biomolecular Chemistry 05/2012; 10(30):6201-10. · 3.70 Impact Factor
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ABSTRACT: 9,10-Dihydroanthracene-9,10-diyl-bridged B(2)(NMe(2))(2) readily adds [H(2)NMe(2)](+), HCl and F(3)CCOOH across its partial B=N double bond(s), thereby forming mono- or diadducts; treatment with 1-iso-propyl-2-mercaptoimidazole leads to a triply B-B-bridged propellane-like structure.
Chemical Communications 05/2012; 48(47):5886-8. · 6.17 Impact Factor
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ABSTRACT: The Au(I) atom of the title compound, [AuI(C(12)H(27)P)], shows an almost linear coordination, with a P-Au-I angle of 178.52 (3)° [Au-P = 2.2723 (14) Å and Au-I = 2.5626 (6) Å].
Acta Crystallographica Section E Structure Reports Online 05/2012; 68(Pt 5):m708. · 0.35 Impact Factor
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ABSTRACT: AbstractThe tetraiodotetrasilane (tBu3Si)SiI2SiI2(SitBu3) can be prepared from precursor (tBu3Si)SiH2SiH2(SitBu3). When (tBu3Si)SiH2SiH2(SitBu3) was treated with an excess of iodine at 120°C, (tBu3Si)SiI2SiI2(SitBu3) was formed. X-ray quality crystals of (tBu3Si)SiI2SiI2(SitBu3) were grown from benzene at ambient temperature. The tetraiodotetrasilane (tBu3Si)SiI2SiI2(SitBu3) crystallizes in the monoclinic space group C2/c, a=10.0110(10)Å, b=13.9130(10)Å, c=25.422(2)Å, β=99.072(4)°, V=3496.6(5)Å3, Z=4, d
calcd=1.829gcm3; R
1=0.0844, wR
2=0.1854 for 3,017 reflections with I>2σ(I). X-ray-crystallographic data show that the bromo and iodo derivatives (tBu3Si)SiX2SiX2(SitBu3) (X=Br, I) are isomorphous. The solid-state structure of (tBu3Si)SiI2SiI2(SitBu3) as well as those of (tBu3Si)SiX2SiX2(SitBu3) (X=Cl, Br) reveals a staggered conformation which adopts a trans-orientation of the supersilyl substituent. Unequal dihedral angles as found in (tBu3Si)SiX2SiX2(SitBu3) (X=Cl, Br, I) indicate that these compounds are sterically overcrowded.
Graphical AbstractIn the solid-state (tBu3Si)SiI2SiI2(SitBu3) features a staggered conformation which adopts a trans-orientation of the supersilyl group. However the solid-state structure of (tBu3Si)SiI2SiI2(SitBu3) reveals unequal dihedral angles.
KeywordsGroup 14 element clusters–Tetrasilanes–Disilanes–Iodosilanes
Journal of Chemical Crystallography 04/2012; 41(2):132-136. · 0.57 Impact Factor
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ABSTRACT: AbstractThe crystal structure of the title compound, C30H42O12Zn3, originally determined from untwinned crystals (Bennett et al. Acta Cryst B 24:904, 1968) has been redetermined from twinned
crystals. The effect of the twinning is that additional reflections appear in the diffraction pattern leading to a unit cell
with a too long c-axis in which the structure cannot be solved. Thus, for a successful structure solution the correct unit cell has to be found
and for refinement the twinning has to be taken into account. The central Zn atom is located on a twofold rotation axis. It
is hexacoordinated in a distorted octahedral mode, whereas the coordination geometry of the two terminal Zn atoms is distorted
trigonal bipyramidal.
Index AbstractThe crystal structure of the title compound, Zinc(II) acetylacetonate trimer, has been redetermined from twinned crystals.
For a successful structure solution the correct unit cell had to be found and for refinement the twinning had to be taken
into account. The central Zn atom is located on a twofold rotation axis. It is hexacoordinated in a distorted octahedral mode,
whereas the coordination geometry of the two terminal Zn atoms is distorted trigonal bipyramidal.
Journal of Chemical Crystallography 04/2012; 38(12):953-957. · 0.57 Impact Factor
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ABSTRACT: The dimeric iron carbonyl [CpFe(CO)(2)](2) and the iodosilanes tBu(2)RSiI were obtained from the reaction of [CpFe(CO)(2)]I with the silanides Na[SiRtBu(2)] (R = Me, tBu) in THF. By the reactions of [CpFe(CO)(2)]I and Na[SiRtBu(2)] (R = Me, tBu) the disilanes tBu(2)RSiSiRtBu(2) (R = Me, tBu) were additionally formed using more than one equivalent of the silanide. In this context it should be noted that reduction of [CpFe(CO)(2)](2) with Na[SitBu(3)] gives the disilanes tBu(3)SiSitBu(3) along with the sodium ferrate [(Na(18-crown-6))(2)Cp][CpFe(CO)(2)]. The potassium analogue [(K(18-crown-6))(2)Cp][CpFe(CO)(2)] (orthorhombic, space group Pmc2(1)), however, could be isolated as a minor product from the reaction of [CpFe(CO)(2)]I with [K(18-crown-6)][PtBu(2)BH(3)]. The reaction of [CpFe(CO)(2)](2) with the potassium benzophenone ketyl radical and subsequent treatment with 18-crown-6 yielded the ferrate [K(18-crown-6)][CpFe(CO)(2)] in THF at room temperature. The crown ether complex [K(18-crown-6)][CpFe(CO)(2)] was analyzed using X-ray crystallography (orthorhombic, space group Pna2(1)) and its thermal behaviour was investigated.
Dalton Transactions 04/2012; 41(22):6671-6. · 3.84 Impact Factor
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ABSTRACT: The title complex, [PdCl(2)(C(18)H(15)P)(2)]·0.5C(6)H(6), has the Pd(II) ion in a square-planar coordination mode (r.m.s. deviation for Pd, P and Cl atoms = 0.024 Å) with the PPh(3) and Cl ligands mutually trans. The benzene solvent mol-ecule is located about a crystallographic inversion centre. The title complex is isostructural with trans-dichloridobis(triphenyl-phosphane)-palladium(II) 1,4-dichloro-benzene sesquisolvate [Kitano et al. (1983 ▶). Acta Cryst. C39, 1015-1017].
Acta Crystallographica Section E Structure Reports Online 04/2012; 68(Pt 4):m507. · 0.35 Impact Factor
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ABSTRACT: Mol-ecules of the title compound, [HgBr(C(9)H(11))], are located on a crystallographic twofold rotation axis. Due to the mol-ecular symmetry, the Hg(II) atom is linearly coordinated by the ipso-C of the mesityl group and the Br atom. In the crystal, mol-ecules lie in planes parallel to (001).
Acta Crystallographica Section E Structure Reports Online 04/2012; 68(Pt 4):m424. · 0.35 Impact Factor
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ABSTRACT: 1,2-Bis(trimethylsilyl)benzenes are key starting materials for the synthesis of benzyne precursors, Lewis acid catalysts, and certain luminophores. We have developed efficient, high-yield routes to functionalized 4-R-1,2-bis(trimethylsilyl)benzenes, starting from either 1,2-bis(trimethylsilyl)acetylene/5-bromopyran-2-one (2) or 1,2-bis(trimethylsilyl)benzene (1)/bis(pinacolato)diborane. In the first reaction, 5 (R = Br) is obtained through a cobalt-catalyzed Diels-Alder cycloaddition. The second reaction proceeds via iridium-mediated C-H activation and provides 8 (R = Bpin). Besides its use as a Suzuki reagent, compound 8 can be converted into 5 with CuBr(2) in i-PrOH/MeOH/H(2)O. Lithium-bromine exchange on 5, followed by the addition of Me(3)SnCl, gives 10 (R = SnMe(3)), which we have applied for Stille coupling reactions. A Pd-catalyzed C-C coupling reaction between 5 and 8 leads to the corresponding tetrasilylbiphenyl derivative. The bromo derivative 5 cleanly undergoes Suzuki reactions with electron-rich as well as electron-poor phenylboronic acids.
The Journal of Organic Chemistry 03/2012; 77(7):3518-23. · 4.45 Impact Factor
