Br Distances Research Articles

1,1′-Dibromoferrocene

The structure of 1,1′-di­bromo­ferrocene, [Fe(C5H4Br)2], has been determined by single-crystal X-ray diffraction at 100 K. The two Br substituents are eclipsed in the solid state, with a Br⋯Br distance of 3.6172 (6) A.

Oxidation of CS4 by AsBr4+: the unexpected formation of the simple CS2Br3+ carbenium ion.

During the preparation of AsBr4(+)[Al(OR)4]-, the novel carbocation CS2Br3+ was synthesized by reaction of AsBr3, Br2, CS2, and Ag[Al(OR)4] (R=C(CF3)3). CS2Br3(+)[Al(OR)4]- was characterized by its crystal structure, NMR and IR spectroscopy, and quantum chemical calculations (including COSMO solvation enthalpies). Additional experiments as well as the computed thermodynamics indicated two likely reaction pathways: Ag(+) +2Br2 +CS2-->CS2Br3(+) +AgBr and the direct 4e- oxidation reaction AsBr4(+) +CS2-->CS2Br3(+) + 1/6As6Br6. Both reactions were observed experimentally and were calculated to be exergonic in solution by -226 and -56 kJ mol(-1) respectively. As a result of charge delocalization the C-S and C-Br distances in the cation are shortened by 0.06 to 0.08 A; the S--Br distances are also slightly shortened indicating a delocalization of the charge also to the bromine atoms in the (S--Br moieties. Based on an analysis of the cation-anion contacts as well as quantum chemical MP2 calculations, a delocalization model as a planar 10 pi electron system is discussed and the pi molecular orbitals are given. It will be shown that the electronic situation of CS2Br3+ is very close to that in CBr3+, that is, the properties of SBr moieties and Br atoms as pi donors towards a formal C+ center are comparable.

Catena-Poly[[dibromozinc(II)]-di-μ-1,4-dioxan-κ2O:O′

The title compound, [ZnBr2(C4H8O2)]n or ZnBr2·(dioxan), has a zigzag chain structure in which the 1,4-dioxan mol­ecules link tetrahedrally coordinated Zn atoms. Each dioxan ring sits on a centre of symmetry. The Zn—Br distances are 2.3110 (8) and 2.3169 (8) A, and angle Br1—Zn1—Br2 is 124.53 (3)°. The Zn—O distances are 2.054 (4) and 2.043 (3) A, and angle O—Zn—O is 89.6 (15)°.

Crystal structure of bis( N-methylethylenediammonium) hexabromodicuprate(I)

The crystal structure of the title compound (C 3H 12N 2) 2Cu 2Br 6, is monoclinic, space group P2 1/ n, with lattice constants a=8.222(2), b=11.214(2), c=10.646(2) Å, β=91.97(1)° and V=981.0(3) Å 3. The structure contains anionic Cu 2Br 6 2− dimers and N-methylethylenediammonium (henceforth MEDA 2+) cations. The centrosymmetric dimer units are composed of two edge-shared CuBr 4 tetrahedra, with bridging Cu–Br distances 0.08 Å longer than the terminal distances. A pair of MEDA 2+ cations hydrogen bond to each dimer via two of the –NH 3 + hydrogen atoms and one of the –NH 2 +- hydrogen atoms. Additional hydrogen bonding between the cations and anions tie the structure together in a complex supramolecular network.

Synthesis of a new donor, BEDT-HBDST and crystal structures, electrical and magnetic properties of (BEDT-HBDST) 2MX4 ( M=Fe, Ga, X=Cl, Br), where BEDT-HBDST=2,5-bis(4,5-ethylenedithio-1,3-diselenol-2-ylidene)-2,3,4,5-tetrahydrothiophene

A novel conjugation-elongated bis(ethylenedithio)tetraselenafulvalene (BETS) type donor, 2,5-bis(4,5-ethylenedithio-1,3-diselenol-2-ylidene)-2,3,4,5-tetrahydrothiophene (BEDT-HBDST) and its magnetic and non-magnetic anion salts, (BEDT-HBDST) 2 MX 4 ( MX 4 −=FeCl 4 −, GaCl 4 −, FeBr 4 − and GaBr 4 −), were prepared. These four salts are isostructural and belong to the space group of P2/ c. They showed semiconducting behavior with small activation energies (59–64 meV). The band structures of these salts are quasi one-dimensional and there is a midgap between the upper band and the lower band, since the degree of dimerization is significant in the stacking direction. The MX 4 − ions are located between the donor columns and near to the ethylenedithio moieties of the donor molecules. The magnetic susceptibilities of the FeCl 4 − and FeBr 4 − salts follow the Curie–Weiss law with Curie constants of 4.6 and 4.8 emu K mol −1 (sum of the spins of S=5/2 and S=1/2) and negative Weiss temperatures of θ=−1.2 and −4.9 K, respectively, revealing a weak antiferromagnetic interaction of 3d spins of the FeCl 4 − and FeBr 4 − anions. The Fe⋯Fe (6.66–7.60 Å), Cl⋯Cl (4.81–4.82 Å) and Br⋯Br (4.74–4.77 Å) distances in the crystal structures of these salts are significantly long. Therefore, the direct magnetic interaction between the 3d spins of the nearest neighboring Fe 3+ ions appears to be not readily accessible.

Binucleartrans-μ-pyrazine-bis[bromotetrapyridineruthenium(II)] dihexafluorophosphate dimethylformamide disolvate

The Ru atoms of the title compound, [Ru2Br2(C4H4N2)(C5H5N)8](PF6)2.2C3H7NO, are coordinated by the four N atoms of the pyridine (py) ligands and a bromide. Two such units are bridged by a pyrazine (pz) unit, which is disposed about a centre of inversion, so as to form a trans pseudo-octahedral geometry about Ru. The py units are in an eclipsed conformation when viewed down the internuclear axis. The Ru—N(pz) distance is 2.079 (3) Å, while the Ru—Br distance is 2.5524 (4) Å.

Synthesis and Crystal Structure of Bis(methyltriethylammonium) Hexabromotellurate(IV)‐tris{dibromodiselenate(I)}, [NMeEt3]2n[TeBr6(Se2Br2)3]n, Containing a Chain‐Polymeric Mixed‐valence Bromotellurate(IV)‐Selenate(I) Anion

AbstractRed crystals of [NMeEt3]2n[TeBr6(Se2Br2)3]n (1) were isolated when selenium and bromine (1:1) were allowed to react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriethylammonium bromide (1:2). The salt 1 crystallizes in the monoclinic space group C2/c with the cell dimensions a = 27.676(6) Å, b = 9.665(2) Å, c = 18.796(4) Å and ß = 124.96(3)° (120 K). The [TeBr6(Se2Br2)3]2— anions contain nearly regular octahedral [TeBr6]2— ions which are incorporated into a polymeric chain by bonding contacts between 3 facial bromo ligands and 3 Se2Br2 molecules, one of which is situated on the twofold symmetry axis. The distances between the μBr ligands and the SeI atoms of the Se2Br2 molecules are observed in the range 3.308(2) — 3.408(2) Å and can tentatively be interpreted as donor‐acceptor bonds with μBr as donors and Se2Br2 as acceptors. The TeIV—Br distances are in the range 2.669(1) — 2.687(1) Å. The bond lengths in the connecting Se2Br2 molecules are: SeI—SeI = 2.267(2) and 2.281(2) Å, SeI—Br = 2.340(1), 2.353(1) and 2.337(1) Å.

Synthesis and Crystal Structure of the (batre)[CuBr 4 ] Complex, where Batre is bis ‐1,1′‐(4‐amino‐1,2,4‐triazolio)ethane

The (batre)[CuBr4] complex is produced by the reaction of CuBr2 and (batre)Br2 in concentrated HBr; its crystal structure is determined. The acentric unit cell (Pn space group) has the following parameters: a = 7.626(2)A, b = 8.945(2)A, c = 11.702(2)A, β = 96.69(3)°, V = 792.8(3)A3, and Z=1 ((batre)[CuBr4] composition). The structure of the complex is built up of [CuBr4]2- tetrahedral anions and (batre)2+ uncoordinated cations. The Cu—Br distances are 2.362–2.385A and the BrCuBr angles are 99.73–129.79°.

Synthesis and Crystal Structure of Bis(methyltriphenylphosphonium) Hexabromotellurate(IV)‐bis{dibromoselenate(II)}, [PMePh3]2[TeBr6(SeBr2)2], the Salt of a Mixed‐valence Bromotellurate(IV)‐Selenate(II) Anion

AbstractBrown crystals of [PMePh3]2[TeBr6(SeBr2)2] (1) were obtained when selenium and bromine (1:1) react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriphenylphosphonium bromide. The salt 1 crystallizes in the triclinic space group P1¯ with the cell dimensions a = 10.3630(14)Å, b = 11.5140(12)Å, c = 11.7605(17)Å, α = 108.643(9)°, β = 106.171(10)° and γ = 99.077(9)° (296 K). In the solid state the [TeBr6(SeBr2)2]2— anion contains a nearly regular [TeBr6] octahedron where the four equatorial bromo ligands each have developed a bond to the SeII atom of a SeBr2 molecule. The contacts between the bridging bromo and the SeII atoms of the SeBr2 molecules are observed in the range 3.11—3.21Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr2 molecules as acceptors. The TeIV—Br distances are in the range 2.67—2.72Å, and the SeII—Br bond lengths in coordinated SeBr2 molecules in the range 2.33—2.34Å.

6-(2-Hydroxyethyl)benzo[f]-1,7-naphthyridin-6-ium bromide

The title compound, C14H13N2O+·Br−, in the solid state, has a zigzag packing of the aza­aromatic mol­ecules in the c direction, forming positively charged columns for the Br− anions. The C—N—C angle at the substituted N atom [122.7 (5)°] is significantly larger than that at the unprotonated N atom [115.8 (5)°]. As for previously known aza­aromatic halides and polyhalides, the title compound also has a short H⋯Br distance for the C—H⋯Br interaction.

5-Benzo[c]-1,5-naphthyridinium bromide

The title compound, C12H9N2+·Br−, crystallizes in the triclinic system (P\overline 1); it is not isostructural with its chloride analogue, which is monoclinic, P21/c. As in the case of the earlier known aza­aromatic chlorides and iodides, we also observed a short H⋯Br distance for the C—H⋯Br interaction.

2,6-Dibromo-4-fluorobenzonitrile

The title compound, C7H2Br2FN, packs in approximately planar sheets with mol­ecules held together in pairs by CN⋯Br intermolecular Lewis acid–base interactions across a center of symmetry. The CN⋯Br arrangement is approximately linear at the Br atom and bent at the N atom, with an N⋯Br distance of 3.11 Å. The molecular pairs form sheets through C—H⋯N hydrogen bonds, with H⋯N distances of 2.55 Å, and C—H⋯F hydrogen bonds with H⋯F distances of 2.68 Å.

Reaction of Tetraphenylantimony Bromide with o-Tolylbismuth Bis(2,5-dimethylbenzenesulfonate). The Formation of Tetranuclear Anion [Bi4Br16]4–

The [Ph4Sb]4[Bi4Br16] complex was synthesized via reaction of tetraphenylantimony bromide with o-tolylbismuth bis(2,5-dimethylbenzenesulfonate) and studied using X-ray diffraction analysis. This compound has ionic structure and consists of tetraphenylstibonium cations and a four-charge tetranuclear anion [Bi4Br16]4– formed by two pairs of edge-sharing ВiBr6 octahedra. The Sb–C bond lengths are equal to 2.05(1)–2.10(1) A, the Bi–Br distances lie within the 2.649(2)–3.246(2) A range, and the Sb(1)···Br(7) distance is equal to 3.934(2) A.

X-ray absorption study of molten yttrium trihalides.

The local structure and structural changes in molten YCl3-LiCl-KCl and molten YBr3-LiBr systems have been investigated by using a high-temperature extended X-ray absorption fine structure (EXAFS) technique. The behaviour of octahedral coordination of the halide ion (Cl(-) and Br(-)) around the Y(3+) ion has been studied by EXAFS of the Y K-absorption edge. The nearest Y(3+)-Cl(-) and Y(3+)-Br(-) distances and coordination numbers of halide ions around the Y(3+) ion do not change by mixing with the alkali halides. The stabilization of the (YCl6)(3-) and (YBr6)(3-) octahedral coordination by adding alkali halides was suggested by decreasing the Debye-Waller factor and the anharmonicity in the nearest Y(3+)-Cl(-) and Y(3+)-Br(-) interactions. The bridging structure of the (YBr6)(3-) octahedra sharing a Br(-) ion in the molten YBr3-LiBr system was studied by EXAFS of the Br K-absorption edge. The coordination number of Y(3+) around the Br(-) ion decreases from 2 in the pure melt to almost 1 in the 30mol% and 15mol% YBr3 melts. This suggests that the bridging is almost broken and the stable octahedron exists freely in the LiBr-rich melts.

(7-endo-Bromocamphorylsulfonyl)imine

[3aS-(3aα,6α,7β)]-7-Bromo-4,5,6,7-tetra­hydro-8,8-di­methyl-3H-3a,6-methano-2,1-benziso­thia­zole 2,2-dioxide, C10H14BrNO2S, has the (−)-camphorsulfon­imine structure, with the Br atom β-oriented. The C—Br distance is 1.941 (5) A, the S—N distance is 1.687 (3) A, and the C=N distance is 1.271 (6) A.

Halogen···halogen versus OH···O supramolecular interactions in the crystal structures of a series of halogen and methyl substituted cis-9,10-diphenyl-9,10-dihydroanthracene-9,10-diols

The crystal structures of four p-phenyl-substituted cis-9,10-diphenyl-9,10-dihydroanthracene-9,10-diols, carrying chloro- ( 1), bromo- ( 2), iodo- ( 3) and methyl substituents ( 4), respectively (with 2 being a previously described compound), have been studied in order to compare the effects of these substituents on the crystalline architecture. Ordinary O–H···O hydrogen bonds govern the packing of the methyl-substituted molecules in 4, whereas interhalogen interactions in competition with conventional hydrogen bonds direct the crystalline arrangement of the halogenated homologues 1– 3, yielding somewhat lower symmetry and lower packing coefficient for the latter crystals. All short (Cl···Cl<3.49, Br···Br<3.46, I···I<3.86 Å) interhalogen interactions are symmetrical type-I connections with more or less “head-on” directions, where increasing size of the connected halogens seems to increase a tendency towards deviation from the ideal head-on geometry. Substitution of methyl in 4 for chlorine in 1 changed the crystal packing significantly, whereas the chloro-substituted derivative ( 1) was found to form a crystal isostructural with its bromo-substituted analogue ( 2). Two of the short interchloro distances in 1 were found to be slightly longer than the corresponding ones in the bromo analogue. This is rather unusual, although extensive inspection of the literature and the Cambridge Structural Database yielded five more examples of pairs of organic chloro and bromo analogues, forming isostructural crystals with direct Cl···Cl contact distances equal to or slightly longer than the corresponding Br···Br distances.

Mechanistic aspects of the reaction between Br2 and chalcogenone donors (LE; E=S, Se): competitive formation of 10-E-3, T-shaped 1:1 molecular adducts, charge-transfer adducts, and [ (LE)2]2+ dications.

The synthesis and spectroscopic characterisation of the products obtained by treatment of N,N'-dimethylimidazolidine-2-thione (1), N,N'-dimethylimidazolidine-2-selone (2), N,N'-dimethylbenzoimidazole-2-thione (3) and N,N'-dimethylbenzoimidazole-2-selone (4) with Br2 in MeCN are reported, together with the crystal structures of the 10-E-3, T-shaped adducts 2 . Br2 (12), 3 . Br2 (13) and 4 . Br2 (14). A conductometric and spectrophotometric investigation into the reaction between 1-4 and Br2, carried out in MeCN, allows the equilibria involved in the formation of the isolated 10-E-3 (E = S, Se) hypervalent compounds to be hypothesised. In order to understand the reasons why S and Se donors can give different product types on treatment with Br2 and I2, DFT calculations have been carried out on 1-8, 19 and 20, and on their corresponding hypothetical [LEX]+ cations (L = organic framework; E = S, Se; X = Br, I), which are considered to be key intermediates in the formation of the different products. The results obtained in terms of NBO charge distribution on [LEX]+ species explain the different behaviour of 1-8, 19 and 20 in their reactions with Br2 and I2 fairly well. X-ray diffraction studies show 12-14 to have a T-shaped (10-E-3; E = S, Se) hypervalent chalcogen nature. They contain an almost linear Br-E-Br (E = S, Se) system roughly perpendicular to the average plane of the organic molecules. In 12, the Se atom of each adduct molecule has a short interaction with the Br(1) atom of an adjacent unit, such that the Se atom displays a roughly square planar coordination. The Se-Br distances are asymmetric [2.529(1) vs. 2.608(1) A], the shorter distance being that with the Br(1) atom involved in the short intermolecular contact. In contrast, in the molecular adducts 13 and 14, which lie on a two-fold crystallographic axis, the Br-E-Br system is symmetric and no short intermolecular interactions involving chalcogen and bromine atoms are observed. The adducts are arranged in parallel planes; this gives rise to a graphite-like stacking. The new crystalline modification of 10, obtained from acetonitrile solution, confirms the importance of short intermolecular contacts in determining the asymmetry of Br-E-Br (E = S, Se) and I-Se-I groups in hypervalent 10-E-3 compounds. The analogies in the conductometric and spectrophotometric titrations of 1 and 2-4 with Br2, together with the similarity of the vibrational spectra of 11-14, also imply a T-shaped nature for 11. The vibrational properties of the Br-E-Br (E = S, Se) systems resemble those of the Br3- and IBr2- anions: the Raman spectrum of a symmetric Br-E-Br group shows only one peak near 160 cm(-1), as found for symmetric Br3- and IBr2- anions, while asymmetric Br-E-Br groups also show an antisymmetric Br-E-Br mode at around 190 cm(-1), as observed for asymmetric Br3- and IBr2- ions. Therefore, simple IR and Raman measurements provide a useful tool for distinguishing between symmetric and asymmetric Br-E-Br groups, and hence allow predictions about the crystal packing of these hypervalent chalcogen compounds to be made when crystals of good quality are not available.

Solvent effects in infrared spectra and ab initio calculations of 2-bromopropane

Detailed study at the Hartree–Fock level regarding the effect of augmentation of 3-21G and 6-31G basis sets provided us with the information about the importance of number of d-type polarisation functions on the optimised geometries of 2-bromopropane, especially the C–Br distance. Vibrational frequencies calculated using 6-31G basis set were scaled with a factor of 0.92, higher than that recommended in literature to obtain concordance with experimental values. The experimental effect of the solvents (the frequency shift from gas to solution) was reproduced as sign and magnitude in the calculations performed with basis sets like 6-31+G(d) in the framework of Onsager's solvent model.

Solvated CrBr2(thf)2, a linear chain in the solid state

In the title compound, di­bromo­bis­(tetra­hydro­furan-O)chromium(II), [CrBr2(C4H8O)2], CrBr2 is solvated by two tetra­hydro­furan (thf) mol­ecules, with a Cr—O distance of 2.072 (3) Å and a Cr—Br distance of 2.5825 (5) Å. The Cr atom lies on the center of inversion. The Cr atom is octahedrally coordinated, with the thf Cr—O bond orthogonal to the Cr—Br bond, and the vacant sites are occupied with a Cr⋯Br intermolecular interaction of 2.9874 (5) Å. The latter interaction is almost orthogonal to the Cr—O vector. This extends the system into a linear chain along the [100] direction.

Rerefinement of decabromodiphenyl ether from new area-detector data

Refinement of the title compound, bis(pentabromophenyl) ether, C12Br10O, from 100 K CCD data yields physically reasonable anisotropic displacement parameters for the C atoms. The C—Br distances are in the range 1.867 (4)–1.891 (4) A and the dihedral angle formed by the phenyl rings is 78.3 (2)°. All endocyclic C—C—C angles are within 0.8 (4)° of the ideal value of 120°.