Synthese und Kristallstruktur der (p-Brombenzyl)triphenylphosphonium-bromide: [(p-Br-C6H4-CH2)P(C6H5)3]+B-;[(p-Br-C6H4-CH2)P(C6H5)3]+Br2- und [(p-Br-C6H4-CH2)P(C6H5)3]+Br3-/ Synthesis and Crystal Structures of (p-Bromobenzyl)triphenylphosphonium Bromides, [(p-Br-C6H4-CH2)P(C6H5)3]+Br-;[(p-Br-C6H4-CH2)P(C6H5)3]+Br- and [(p-Br-C6H4-CH2)P(C6H5)3]+Br3-
TL;DR: In this article, the triclinic structure of triphenylphosphine with p-bromobenzylbromide has been determined and its structure has been shown to have a tetrahedral geometry around the P atom.
Abstract: (p-Bromobenzyl)triphenylphosphonium Bromide, [(p-Br-C₆H₄-CH₂)P(C₆H₅)₃]⁺Br⁻ · (CH₂Cl₂)₂.₅ (1) has been prepared by the reaction of triphenylphosphine with p-bromobenzylbromide and its structure determined (triclinic, space group P1, Z = 2, a = 1198.03(12), b = 1245.80(11), c = 1258.42(12)pm, a = 100.170(8), β = 103.543(9), γ = 1 18.158(7)°. The compound exists as Br⁻ anions and [(p-Br-C₆H₄- CH₂)P(C₂H₅)₃]⁺ cations, with weak interactions between the chlorine atoms of the CH₂Cl₂ molecules and the bromine bonded in the cation. [p-Br-C₆H₄-CH₂)P(C₆H₅)₃]Br₂ (2) and [(p-Br-C₆H₄-CH₂)P(C₆H₅)₃]Br₃·(CH₂Cl₂)₁.₅ (3) have been obtained by reactions of the corresponding amounts of bromine with 1 in methylenechloride solution. The yellow-red crystals of 2 are orthorhombic, space group Pccn, Z = 8, a = 2060.8(3), b = 1223.6(4), c = 1860.8(3) pm. Compound 2 exists as [p-Br-C₆H₄-CH₂)P(C₆HO₅)₃]⁺ cations and linear Br²⁻₄ units with a bromide-bromine distance of 297.3(4) pm. The red crystals of (3) are triclinic, space group P1, Z = 2, a = 1 171.16(7), b = 1260.97(8), c = 1270.35(7)pm, α = 65.510(5), β = 75.811(5), γ = 62.320(5)°, and contain [(p-Br-C₆H₄-CH₂)P(C₆H₅)₃]⁺ cations and linear, slightly asymmetrical Br⁻₃ anions. In all cases the cation has a slightly irregular tetrahedral geometry around the P atom.
Citations
More filters
TL;DR: In this article, a density functional theory approach under the local density approximation (DFT/LDA) was used to describe the formation of polybromide chain structures, their stretching frequency modes and charge transfer induced by the interaction of these molecules with a graphene sheet.
Abstract: We use a density functional theory approach under the local density approximation (DFT/LDA) to describe the formation of polybromide chain structures, their stretching frequency modes and charge transfer induced by the interaction of these molecules with a graphene sheet. In many cases, we find polybromides to be more thermodynamically stable than the equivalent Br2 molecular structures adsorbed on graphene sheet. This results in lower frequency stretch modes at around 170–190 cm−1. We propose that these are rarely observed experimentally due to the bromination techniques used, which introduces molecular Br2 into the carbon host material. Charge transfer with their host material means that these molecules and their associated hole charge in the neighbouring carbon materials, are then coulombically repelled from other bromine molecules which acts as a barrier to combination into polybromides. Our calculated barrier for polybromide formation (2Br2→Br4) on a graphene sheet was 0.35 eV which is an exo...
4 citations
TL;DR: In this treatment, data from the perturbed structures, around the fully optimize structure, are employed for the analysis, in addition to those from the fully optimized one, which represent the dynamic nature of interactions.
Abstract: The nature of Br4 σ(4c-6e) of the BBr-∗-ABr-∗-ABr-∗-BBr form is elucidated for SeC12H8(Br)SeBr---Br-Br---BrSe(Br)C12H8Se, the selenanthrene system, and the models with QTAIM dual functional analysis (QTAIM-DFA). Asterisks (∗) are employed to emphasize the existence of bond critical points on the interactions in question. Data from the fully optimized structure correspond to the static nature of interactions. In our treatment, data from the perturbed structures, around the fully optimized structure, are employed for the analysis, in addition to those from the fully optimized one, which represent the dynamic nature of interactions. The ABr-∗-ABr and ABr-∗-BBr interactions are predicted to have the CT-TBP (trigonal bipyramidal adduct formation through charge transfer) nature and the typical hydrogen bond nature, respectively. The nature of Se2Br5 σ(7c-10e) is also clarified typically, employing an anionic model of [Br-Se(C4H4Se)-Br---Br---Br-Se(C4H4Se)-Br]-, the 1,4-diselenin system, rather than (BrSeC12H8)Br---Se---Br-Br---Br-Se(C12H8Se)-Br, the selenanthrene system.
1 citations
01 Jan 2016
TL;DR: In this paper, a density functional theory approach under the local density ap- proximation (DFT/LDA) was used to describe the formation of polybromide chain structures, their stretching frequency modes and charge transfer induced by the interaction of these molecules with a graphene sheet.
Abstract: 6 Abstract: We use a density functional theory approach under the local density ap- proximation (DFT/LDA) to describe the formation of polybromide chain structures, their stretching frequency modes and charge transfer induced by the interaction of these molecules with a graphene sheet. In many cases, we find polybromides to be more thermodynamically stable than the equivalent Br 2 molecular structures ad- sorbed on graphene sheet. This results in lower frequency stretch modes at around 170-190 cm −1 . We propose that these are rarely observed experimentally due to the bromination techniques used, which introduces molecular Br 2 into the carbon host material. Charge transfer with their host material means that these molecules and their associated hole charge in the neighbouring carbon materials, are then coulom- bically repelled from other bromine molecules which acts as a barrier to combina- tion into polybromides. Our calculated barrier for polybromide formation (2Br 2 →Br 4 ) on a graphene sheet was 0.35 eV which is an exothermic process with an enthalpy