Bromide Analogues Research Articles

Catalytic properties of iridium-tin complexes in the hydrogenation of cyclohexene and hexene-1

The physicochemical and catalytic properties of halogen-containing indium-tin complexes with dimethylsulfoxide (DMSO), dimethylacetamide (DMA) or dimethylformamide (DMF) ligands have been studied in the hydrogenation of cyclohexene and hexene-1. Complexes containing chloride and DMSO were less effective catalysts than complexes containing DMA and DMF and than their bromide analogs. Catalytic activity of the iridium-tin complexes increased with variation of the solvent: methanol < acetone < dimethylformamide. Formation of hexane goes via an isomerization step with the catalyst containing chloride and DMA, whereas hydrogenation of hexene-1 and its isomerization occur in parallel with the analogous catalyst containing DMSO.

7Li NMR and 35Cl, 81Br NQR Study of Lithium Ion Conductor LiAlX4 (X = Cl and Br)

Abstract The dynamic behavior of LiAlX4 (X = Cl and Br) was studied by means of 7Li NMR and 35Cl, 81Br NQR spectroscopies. The motional narrowing processes of the 7Li NMR due to Li+ diffusion were observed above room temperature for single crystals of LiAlX4. The activation energies for these processes were 43.4 and 42.1 kJ mol−1 for the chloride and bromide analogs, respectively. A stepwise decrease in the 7Li NMR quadrupole splitting suggested that the Li nucleus sees time averaged electric field gradient (EFG) arising from several different sites. The modulation effect of Li+ diffusion on the NQR relaxation times was detected only for LiAlBr4 but not for the chloride analog.

The redox chemistry of the triply bonded compounds Re 2X 4(μ-dmpm) 3 (XCl or Br; dmpm=Me 2PCH 2PMe 2) and the isolation and characterization of the nitrosyl complex Re 2Cl 5(μ-dmpm) 2(NO)

The current literature on multiply bonded dirhenium complexes that contain the bis(dimethylphosphino)methane ligand (abbreviated dmpm) is reviewed. New procedures are described for the synthesis of the complex Re 2Cl 4(μ-dmpm) 3. The analogous bromide and iodide complexes of stoichiometry Re 2X 4(μ-dmpm)3 have been prepared by the reactions of Re 2Br 4(μ-dppm) 2 (dppm=Ph 2PCH 2PPh 2) and Re 2X 4(PR 3) 4 (XBr or I; REt or Pr n) with dmpm. The reactions of Re 2X 4(μ-dmpm) 3 (XCl or Br) with NOPF 6 in dichloromethane give the paramagnetic species [Re 2X 4(μ-dmpm) 3]PF 6. The chloro complex reacts further with NOPF 6 to afford the diamagnetic complex Re 2Cl 5(μ-dmpm) 2(NO). This is the first triply bonded dimetal complex that contains a nitrosyl ligand and is stabilized to fission of the metal-metal bond. The identity of this complex has been confirmed by a single crystal X-ray structure determination. Crystal data at 20 °C: orthorhombic space group Iba2 (No. 45), a=14.278(3), b=23.966(3), c=13.880(3) Å, V=4749(3) Å, Z=8. The structure was refined by full matrix least-squares to R=0.036 ( R w=0.047) for 1427 data with I>3σ( I). The structure, which can be represented as Cl 3Re(μ-dmpm) 2ReCl 2(NO), contains a terminally bound NO ligand and a cis, trans disposition of the pairs of phosphorus donor atoms at the two metal centers. The ReRe bond distance is 2.379(1) Å.

Synthesis and characterization of the pseudo-1-D mixed-valence (Et4-nMenN)Cu2X4 salts: pinned charge density wave systems exhibiting intervalence charge transfer

A series of mixed-valence Cu(I)/Cu(II) linear chain compounds exhibiting pinned charge density waves have been synthesized. The compounds have stoichiometry ACu[sup I]Cu[sup II]X[sub 4] with X = Cl or Br and A = tetraethylammonium (TEA), triethylmethylammonium (TEM), or diethyldimethylammonium (DEM). The crystal structures of the bromide analogues have been determined. The (TEM)Cu[sub 2]Br[sub 4] salt is tetragonal. The (DEM)Cu[sub 2]Br[sub 4] salt is also tetragonal. The (TEA)Cu[sub 2]Br[sub 4] salt is orthorhombic. These structures reveal infinite chains of alternating Cu[sup I]X[sub 4][sup 3[minus]] and Cu[sup II]X[sub 4][sup 2[minus]] tetrahedra (distorted) sharing edges, the chains being effectively isolated by bulky tetraalkylammonium cations. Although the valence states appear to be localized, with a 0.1 [angstrom] difference in the Cu(I)-X and Cu(II)-X bond lengths, several characterization techniques indicate Robin and Day class II behavior. The data also support a Peierls 4k[sub f] distorted charge density wave state for these chains. All salts show an intervalence charge-transfer band in the visible region of the spectrum. Conductivity measurements indicate semiconductive behavior. Temperature-dependent magnetic susceptibility measurements on (TEA)Cu[sub 2]Br[sub 4] reveal weak antiferromagnetic coupling, which is attributed to short Br[center dot][center dot][center dot]Br contacts between Cu[sup II]X[sub 4][sup 2[minus]] species within the chains. The above physicalmore » properties are rationalized in light of previous EHMO band calculations.« less

Anionic, four-co-ordinate, ten-electron bismuth complexes: aspects of synthesis, structure and bonding

The reaction between [BiCl{Fe(CO)2(η-C5H5)}2]1 and 1 equivalent of [N(PPh3)2]Cl afforded the ionic complex [N(PPh3)2][BiCl2{Fe(CO)2(η-C5H5)}2]2. The [NMe4]+ salt, [NMe4][BiCl2{Fe(CO)2(η-C5H5)}2]3, was prepared similarly. An analogous bromide derivative, [PPh4][BiBr2{Fe(CO)2(η-C5H5)}2]4, was prepared from the reaction between [BiBr{Fe(CO)2(η-C5H5)}2]5 and [PPh4] Br. The reaction between [BiCl{Mo(CO)3(η-C5H5)}2]7 and 1 equivalent of [N(PPh3)2]Cl afforded the complex [N(PPh3)2][BiCl2-{Mo(CO)3(η-C5H5)}2]8; that between [PPh3(CH2Ph)]Cl and 7 afforded [PPh3(CH2Ph)][BiCl2{Mo(CO)3(η-C5H5)}2]9. In tetrahydrofuran (thf) solution some degree of dissociation of [Mo(CO)3(η-C5H5)]– is observed for 8 and 9. The bromide complexes [PPh4][BiBr2{Mo(CO)3(η-C5H5)}2]10 and [NBun4][BiBr2{Mo(CO)3(η-C5 H5)}2]11 were prepared from the reactions between [BiBr{Mo(CO)3(η-C5H5)}2]12 and 1 equivalent of [PPh4]Br and [NBun4] Br respectively. The tungsten complexes [N(PPh3)2][BiCl2{W(CO)3(η-C5 H5)}2]13 and [PPh3(CH2Ph)][BiCl2{W(CO)3(η-C 5H5)}2]14 were similarly prepared. Spectroscopic data for the complexes [N(PPh3)2][BiCl3{Mo(CO)3(η-C5 H5)}]16 and [N(PPh3)2][BiCl3{W(CO)3(η-C5H5)}]17 are also presented. The structures of compounds 2, 8, 9(as a thf solvate) and 13 were determined by X-ray crystallography. The structures of all of the compounds comprise a four-co-ordinate bismuth centre bonded to two chlorine atoms and two MLn fragments. The precise co-ordination geometries, however, vary from close to an idealised equatorially-vacant trigonal bipyramid (disphenoidal), 2 and 9, with axial chlorines and equatorial metal centres, to nearly tetrahedral, 8 and 13. These results are incorporated into a general discussion of the structures found for AB4E complexes, i.e. four-co-ordinate with ten valence electrons, and some ideas are advanced on possible electronic factors which determine the particular geometry adopted.

Induction of higher coordination states in phenyl Grignard reagents by intramolecular coordination. Crystal structures of O-CH2(OCH2CH2)*OCH3-substituted phenylmagnesium bromides (n = 0-3)

A series of phenylmagnesium bromides with intramolecularly coordinating substitents CH 2 -(OCH 2 CH 2 ) n OCH 3 at one [n=0-4] or both [n=1,2] ortho positions has been investigated. The pure Grignard reagents were obtained from the exchange reaction of corresponding arylmercury bromides with magnesium, since their synthesis from analogous bromides and magnesium was accompanied by extensive ether cleavage in the substituents if n>1

Some Observations about the Diffusion Coefficients of Anionic Transition Metal Halide Complexes in Room‐Temperature Haloaluminate Ionic Liquids

Stokes‐Einstein products that were derived from electrochemical data for monomeric and polymeric anionic transition metal halide complexes in the basic aluminum chloride‐1‐methyl‐3‐ethylimidazolium chloride room‐temperature ionic liquid and its bromide analog are shown to vary stepwise with the overall charge on the complex ion. These observations are reconciled in terms of ion‐ion interactions between the melt cations and the anionic complexes which lead to diffusing entities with larger solvodynamic radii than expected. The number of associated cations appears to increase as the charge on the transition metal complex becomes more negative.

ChemInform Abstract: Modelling of Micellar Effects Upon Substitution Reactions with Moderately Concentrated Hydroxide Ion.

AbstractThe cationic surfactants CTACl or the analogous bromide enhance the rates for the hydrolysis of (I) and (III).

Preparation and characterization of glycerol-based cleavable surfactants and derived vesicles

Four cleavable double-chain surfactants were synthesized: [2,2-diheptadecyl-1,3-dioxolan-4-yl) methyl] trimethylammonium methanesulfonate(1a), the analogous bromide(1b), [(2,2-diheptadecyl-1,3-dioxolan-4-yl) methyl] dimethyl(3-sulfopropy) ammonium hydroxide inner salt(1c), and sodium 3-[(2,2-diheptadecyl-1,3-dioxolan-4-yl) methoxyl]-1-propanesulfonate(1d). Vesicles of 1a, 1b, and 1d prepared by sonication were characterized by 1 H NMR line width narrowing, dynamic laser light scattering, differential scanning calorimetry, and dye entrapment and leakage studies

Magnetochemistry of chromium (III) (abstract)

There are relatively few superexchange-coupled antiferromagnets of chromium (III), largely because the exchange interactions are so weak. We have begun a program to study these materials and present magnetic susceptibility measurements on several new systems. We find that a polycrystalline sample of [Cr(NH3)5Cl]Cl2 behaves as a magnetic linear chain, and orders antiferromagnetically at about 600 mK, and that single crystals of [Cr(en)3]X3⋅3H2O order at 130 mK when X is chloride. The analogous bromide orders at 112 mK. The chloride exhibits an easy axis, parallel to the longitudinal axis, while the bromide exhibits an easy plane. The data have been successfully fitted by several different procedures which result in much the same parameters. In addition to the exchange, it is necessary to include in the analysis the zero-field splitting of the chromium ions. The zero-field splitting in paramagnetic NaMg[Cr(oxalate)3]⋅9H2O has also been measured.

Rate constants of the reactions of Re(CO)5 radicals with organic halides determined using esr spectroscopy

1. An ESR spectroscopic study was carried out at 20°C on the photochemically initiated reaction of Re2(CO)10 with monohalo and polyhalo aliphatic and aromatic compounds. 2. In substitution reactions involving breakage of a C-Hal bond, Re(CO)5 is more than three orders of magnitude more active than CpW(CO)3 and more than two or three orders less reactive than Śi(C2H2)2 radicals. 3. The rate constants for halogen abstraction by Re(CO)5 radicals increase by two orders of magnitude in going from the chlorides to the analogous bromides and from monohaloalkanes to allyl halides and then to benzyl halides and from α,α-dichloroalkanes toα,α,α-trichloroalkanes. 4. Comparison of the rate constants for halogen abstraction by Si(C2H5)3 and Re(CO)5 radicals yields an explanation for the high efficiency of the Re2(CO)10 + HSi(C2H5)3 system relative to Re2(CO)10 alone for the generation ofα-chloro radicals.

Magnetic order in a dimerized singlet-triplet system: A neutron scattering study of Cs3Cr2I9.

${\mathrm{Cs}}_{3}$${\mathrm{Cr}}_{2}$${\mathrm{I}}_{9}$ belongs to a class of antiferromagnetic dimerized singlet-triplet compounds. Its magnetic ordering has been studied by elastic neutron scattering and magnetic-susceptibility measurements. A transition to three-dimensional magnetic order is found at 6.8 K. The ordered magnetic dimer moment is K=0.91. The ordering of the iodide is interpreted by relating it to the spin dynamics in the disordered phase which is known for the analogous bromide and chloride compounds. The true soft mode which induces magnetic order is not the singlet-triplet exciton mode but an intratriplet mode. The ordered structure corresponds to a dimerized triangular antiferromagnet. The small incommensurability of the magnetic unit cell is related to the energy minima of the exciton mode in the disordered phase. The temperature dependence of the magnetic moment is interpreted in terms of a two-sublattice antiferromagnetic mean-field model. The interaction parameters are estimated as J=-0.79 meV (intradimer), ${J}_{p}$=-0.13 meV (interdimer, within the basal plane), and ${J}_{c}$=-0.019 meV (interdimer, along c).

Synthesis of NSC‐341,964: An unexpected study on the stability of 2‐aryl‐4H‐3,1‐benzoxazin‐4‐ones

AbstractResynthesis of NSC 341,964, which had been assigned structure 1 (1‐[[3‐(7‐chloro‐4‐oxo‐4H‐3,1‐benzoxazin‐2‐yl)phenyl]methyl]pyridinium chloride) was approached via 7‐chloro‐2‐(3‐methylphenyl)‐4H‐3,1‐benzoxazin‐4‐one (5) obtained from 3‐methylbenzoyl chloride (2) and 2‐amino‐4‐chlorobenzoic acid (3) followed by dehydration in acetic anhydride. Radical bromination provided 6 which with pyridine afforded the bromide analog 7 of 1. Ion exchange, however, gave ring‐opened benzoic acid 8 rather than 1. The original sample of NSC 341,964 also proved to be ring‐opened material. However, 7 upon standing exhibited slow hydrolysis to 8 so that the structure of the original NSC 341,964 remains uncertain. A more direct route to compound 8 is also described.

Dielectric studies of some tri-n-alkylammonium nitrates and perchlorates in benzene solutions at 298.15 K

The partial molar volumes, partial molar refractions and partial molar polarizations of some tri-n-alkylammonium nitrates and perchlorates in benzene solutions have been determined at 298.15 K in the concentration range up to 0.005 mole fraction of solute and are found to be independent of concentration. The dipole moments of the solutes at infinite dilution have been calculated. On the basis of a model of an ion pair with mutually polarizable ions and a permanent dipole moment on the cation, the interionic distance, total electrostatic interaction energy and energy due to the mutual polarization of the ions in an ion pair have been calculated. The interaction energy due to the mutual polarization of ions in the ion pair is found to be an important part of the total electrostatic interaction energy. In addition, it has been shown that the ion pairs investigated belong to the class of contact ion pairs. A comparison of the parameters determined with those of tri-n-alkylammonium halides shows that the values for tri-n-alkylammonium nitrates are close to those of analogous bromides, while those of tri-n-alkylammonium perchlorates are close to those of iodides. This is in accordance with the nearly equal crystallographic radii of nitrate and bromide ions, as well as of perchlorate and iodide ions.

Transition metal complexes of primary and secondary phosphines, part I. Reactions between palladium(II) halides and some primary and secondary phosphines

Reactions between PdCl2 or [PdCI4]2−, in nonpolar solvents and phosphines R2PH or RPH2 (R = cyclohexyl, 2-cyanoethyl) yield new complexes ofcis- L2PdCl2 type, which were characterized by their spectral properties. In polar solvents these complexes react further to give bridged µ-phosphido complexes. Analogous bromides can be prepared by adding LiBr to the reaction mixtures.

Reaction of tungsten(VI) tetrachloride sulphide and selenide and the analogous bromides with a range of donor molecules

The compounds WX4Y (Y = S and Se, X = Cl and Br) have been allowed to react with a range of ligands containing nitrogen, phosphorus, oxygen, and sulphur donor atoms. Simple six-co-ordinate adducts WX4Y,L and 2WX4Y,L' (L = unidentate and L' = bidentate ligand) have been isolated in many cases and characterised. In these adducts the terminal WY bond is retained. Under more severe reaction conditions, longer reaction period or higher temperatures, tungsten can be reduced to the quinquevalent or quadrivalent state. Thus MeSCH2CH2SMe (mte) gives WCl3S,mte, while triphenylphosphine both reduces tungsten and extracts sulphur or selenium to give tungsten(IV) adducts of the type WX4,PPh3,P(Y)Ph3.

Solids with high ionic conductivity in group 1 halide systems

Phase diagrams have been determined for the systems MI+AgI (M = Na, K, Rb, Cs, Tl or NH4), MBr+AgBr (M = K, Rb or Cs) and MI+CuI (M = K or Rb). A group of isomorphous compounds MAg4I5(M = K, Rb, NH4) with exceptionally high ionic conductivity has been identified. At 20°C the conductivity of polycrystalline RbAg4I5 is 0.124 ± 0.006 ohm–1 cm–1, i.e., higher than the ionic conductivity of any other known solid. At this temperature RbAg4I5 is stable, but KAg4I5 and NH4Ag4I5 slowly disproportionate to AgI and K2AgI3 or (NH4)2AgI3. The ternary system KI+RbI+AgI contains a complete range of solid solutions (K,Rb) Ag4I5. Analogous bromides have not been found, but a compound KCu4I5 is stable between 257 and 332°.

Small-Ring Compounds. XXXVI. 3-Methylenecyclobutyl Bromide and 1-Methylcyclobut-2-enyl Bromide

3-Methylenecyclobutyl bromide and 1-methylcyclobut-2-enyl bromide have been synthesized from the cycloaddition products of allene with acrylonitrile and vinyl benzoate. The rate constants for solvolysis of the two bromides in aqueous ethanol have been determined and correlated with the solvolysis rates of a series of analogous bromides. 1-Methylcyclobut-2-enyl bromide appears to exhibit some rate enhancement due to cross-ring s-type interaction of the electrons formally centered on the 3-position with the electron-deficient 1-position in the transition state.