Stereoselective Total Synthesis of (11β)‐11‐Methoxycurvularin

A simple and highly efficient stereoselective total synthesis of (11β)‐11‐methoxycurvularin ( 5 ), a polyketide natural product, was achieved. The synthesis commenced with a Cu‐mediated regioselective opening of (2S)‐2‐methyloxirane ( 6 ) and comprised a Keck asymmetric allylation and intramolecular Friedel–Crafts acylation as key steps (Scheme 2).     

Dimeric Structure of [(η2‐NO3)2(tpy)Bi(μ‐OH)2Bi(tpy)(η2‐NO3)2]

The synthesis and single crystal X‐ray structure determination are reported for the 2,2′ : 6′,2″‐terpyridine (= tpy) adduct of bismuth(III) nitrate. The hydroxide‐bridged dimer [(η²‐NO₃)₂(tpy)Bi(μ‐OH)₂Bi(tpy)(η²‐NO₃)₂] with nine‐coordinate geometry about Bi was the only isolable product from all crystallization attempts in varying ratios of Bi(NO₃) : terpy.; [(η²‐NO₃)₂(tpy)Bi(μ‐OH)₂Bi(tpy) · (η²‐NO₃)₂] is triclinic, P 1, a = 7.941(8), b = 10.732(9), c = 11.235(9) Å; α = 63.05(1), β = 85.01(1), γ = 79.26(1)°, Z = 1, dimer, R = 0.058 for N₀ = 2319.     

LaMn11C2–x und PrMn11C2–x,Carbide mit gefüllter BaCd11-Struktur

LaMn₁₁C_2–x and PrMn₁₁C_2–x, Carbides with Filled BaCd₁₁ Structure The new compounds LaMn₁₁C_2–x and PrMn₁₁C_2–x were obtained by reaction of the elements in a high-frequency furnace with subsequent annealing. The compounds crystallize tetragonal, space group I4₁/amd, with Z = 4 formula units per cell. The lattice constants are a = 10.4134(4) Å, c = 6.7293(4) Å for LaMn₁₁C_2–x and a = 10.372(1) Å, c = 6.715(1) Å for PrMn₁₁C_2–x. The structure of LaMn₁₁C_2–x was determined from single-crystal diffractometer data and refined to a residual of R = 0.013 for 24 variables and 503 structure factors. The positions of the metal atoms correspond to those of BaCd₁₁. The carbon atoms fill octahedral voids formed by four Mn and two La atoms with an occupancy of 76 ± 1%. This corresponds to the formula LaMn₁₁C_1.52. The structure and chemical bonding of the compound are discussed.     

(Bzl4P)2[Bi2I8] – ein Iodobismutat mit fünffach koordiniertem Bi3+‐Ion

(Bzl₄P)₂[Bi₂I₈] – an Iodobismuthate with Penta‐coordinated Bi³⁺ Ions (Bzl₄P)₂[Bi₂I₈] ( 1 , Bzl = –CH₂–C₆H₅) is the first iodobismuthate showing square pyramidal coordination of the Bi³⁺ ion. The anion structure of 1 is compared with that of (Ph₄P)₂[Bi₂I₈(thf)₂] ( 2 ), in which the vacant coordination sites in 1 are occupied by THF ligands. (Bzl₄P)₂[Bi₂I₈] ( 1 ): Space group P1 (No. 2), a = 1300.6(6), b = 1316.8(6), c = 2157.0(9) pm, α = 78.66(3), β = 87.17(3), γ = 60.62(3)°, V = 3151(2)_.10⁶ pm³; (Ph₄P)₂[Bi₂I₈(thf)₂] ( 2 ): Space group P1 (No. 2), a = 1146.5(1), b = 1181.2(1), c = 1249.2(1) pm, α = 92.28(1), β = 105.71(1), γ = 95.67(1)°, V = 1616.6(2)_.10⁶ pm³.     

Undecahalo‐closo‐undecaborates [B11Hal11]2–

The closo‐undecaborate A₂[B₁₁H₁₁] (A = NBzlEt₃) can be halogenated with excess N‐chlorosuccine imide, bromine or iodine, respectively, to give the perhalo‐closo‐undecaborates A₂[B₁₁Hal₁₁] (Hal = Cl, Br, I). The chlorination in the 11 : 1 ratio of the reagents yields A₂[B₁₁HCl₁₀], whose subsequent iodination makes A₂[B₁₁Cl₁₀I] available. The three type [B₁₁Hal₁₁]^2– anions show only one and the two type [B₁₁Cl₁₀X]^2– anions (X = H, I) only two ¹¹B NMR peaks in the ratio 10 : 1, thus exhibiting the same degenerate rearrangement of the octadecahedral B₁₁ skeleton as is well‐known for [B₁₁H₁₁]^2–. The crystal structure analysis of A₂[B₁₁Br₁₁] and A₂[B₁₁I₁₁] reveals a rigid octadecahedral skeleton in the solid state, up to 330 K, whose B–B bond lengths deviate more or less from the idealized C_2v gas phase structure, but are in good accordance with the distances of A₂[B₁₁H₁₁]. Electrochemical experiments elucidate the mechanism of the known oxidation of [B₁₁H₁₁]^2– to give [B₂₂H₂₂]^2–: A first one‐electron transfer is followed by the dimerization of the [B₁₁H₁₁]^– monoanion, whereas neutral B₁₁H₁₁, a presumably most reactive species, does not play a role as an intermediate. The electrochemical oxidation of [B₁₁Hal₁₁]^2– anions also starts with a one‐electron transfer, which is perfectly reversible only in the case of Hal = Br. There is no electrochemical indication for the formation of [B₂₂Hal₂₂]^2–. The neutral species B₁₁Hal₁₁ should be a short‐lived, very reactive species.     

Bi9Rh2Br3, Bi9Rh2I3 und Bi9Ir2I3 – Eine neue Strukturfamilie quasi‐eindimensionaler Metalle

Bi₉Rh₂Br₃, Bi₉Rh₂I₃, and Bi₉Ir₂I₃ – A New Structure Family of Quasi One‐dimensional Metals Bi₉Rh₂Br₃, Bi₉Rh₂I₃, and Bi₉Ir₂I₃ were synthesized from the elements using niobium bromides or iodides as auxiliaries to modify the partial pressures in the course of the reaction. X‐ray diffraction on single crystals showed that the compounds are not isomorphous. However they have a common structural principle: strands of condensed [MBi₈] polyhedra, which are separated by halide anions. The spatial arrangement of the [MBi_1/1Bi_7/2] strands differs with the combination of elements: In Bi₉Rh₂I₃ (monoclinic, P2₁/m (no. 11), a = 775.6(1), b = 1374.9(2), c = 901.1(2) pm, β = 109.29(2)°) all strands are oriented parallel to each other. Bi₉Rh₂Br₃ (monoclinic, P2₁/m (no. 11), a = 927.98(8), b = 1372.1(1), c = 1992.7(2) pm, β = 100.77(1)°) and Bi₉Ir₂I₃ (orthorhombic, Pnma (no. 62), a = 2677.5(5), b = 1394.2(2), c = 967.6(1) pm) are ordered polytypes with two orientations changing in alternating layers of characteristic widths. The experimental proof of metallic conductivity in Bi₉Ir₂I₃ supports the assumption of delocalised electrons inside the  [MBi_1/1Bi_7/2] strands. The magnetic susceptibility of Bi₉Rh₂Br₃ increases slowly with decreasing temperature and shows a local maximum at about 14 K.     

ChemInform Abstract: Crystal Growth,Crystal Structure of New Polymorphic Modification, β‐Bi2B8O15 and Thermal Expansion of α‐Bi2B8O15.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Bi3+‐Er3+ and Bi3+‐Yb3+ Codoped Cs2AgInCl6 Double Perovskite Near‐Infrared Emitters

Bi³⁺ and lanthanide ions have been codoped in metal oxides as optical sensitizers and emitters. But such codoping is not known in typical semiconductors such as Si, GaAs, and CdSe. Metal halide perovskite with coordination number 6 provides an opportunity to codope Bi³⁺ and lanthanide ions. Codoping of Bi³⁺ and Ln³⁺ (Ln=Er and Yb) in Cs₂AgInCl₆ double perovskite is presented. Bi³⁺‐Er³⁺ codoped Cs₂AgInCl₆ shows Er³⁺ f‐electron emission at 1540 nm (suitable for low‐loss optical communication). Bi³⁺ codoping decreases the excitation (absorption) energy, such that the samples can be excited with ca. 370 nm light. At that excitation, Bi³⁺‐Er³⁺ codoped Cs₂AgInCl₆ shows ca. 45 times higher emission intensity compared to the Er³⁺ doped Cs₂AgInCl₆. Similar results are also observed in Bi³⁺‐Yb³⁺ codoped sample emitting at 994 nm. A combination of temperature‐dependent (5.7 K to 423 K) photoluminescence and calculations is used to understand the optical sensitization and emission processes.     

Bi37InBr48: Eine polares Subhalogenid mit Bi95+‐Polykationen,komplexen Bromobismutat(III)‐Anionen [Bi3Br13]4— und [Bi7Br30]9— sowie Pentabromoindat(III)‐Anionen [InBr5]2—

Bi₃₇InBr₄₈: a Polar Subhalide with Bi₉⁵⁺ Polycations, Complex Bromobismuthate(III) Anions [Bi₃Br₁₃]^4— and [Bi₇Br₃₀]^9—, and Pentabromoindate(III) Anions [InBr₅]^2— Black crystals of Bi₃₇InBr₄₈ were synthesized from bismuth, indium and BiBr₃ by cooling stoichiometric melts from 570 K to 470 K. X‐ray diffraction on powders and single‐crystals revealed that the compound crystallizes with space group P 6₃ (a = 2262.6(4); c = 1305.6(2) pm). The Bi₉⁵⁺ polycations in the polar crystal structure have the shape of heavily distorted tri‐capped trigonal prisms with approximate C_s symmetry. The high complexity of the structure results from three coexisting types of anionic groups: Three edge‐sharing [BiBr₆] octahedra constitute the trigonal bromobismuthate(III) anion [Bi₃Br₁₃]^4—. Four [BiBr₆] and three [BiBr₅] polyhedra share common vertices to form the [Bi₇Br₃₀]^9— hemi‐sphere, in which the trigonal bipyramid of the pentabromoindat(III) ion [InBr₅]^2— is embedded.     

1‐Oxa‐nido‐dodecaborate [OB11H12]− from the Controlled Oxidation of the closo‐Borates [B11H11]2− and [B12H12]2−

The closo‐dodecaborate [B₁₂H₁₂]^2? is degraded at room temperature by oxygen in an acidic aqueous solution in the course of several weeks to give B(OH)₃. The degradation is induced by Ag²⁺ ions, generated from Ag⁺ by the action of H₂S₂O₈. Oxa‐nido‐dodecaborate(1?) is an intermediate anion, that can be separated from the reaction mixture as [NBzlEt₃][OB₁₁H₁₂] after five days in a yield of 18 %. The action of FeCl₃ on the closo‐undecaborate [B₁₁H₁₁]^2? in an aqueous solution gives either [B₂₂H₂₂]^2? (by fusion) or nido‐B₁₁H₁₃(OH)^? (by protonation and hydration), depending on the concentration of FeCl₃. In acetonitrile, however, [B₁₁H₁₁]^2? is transformed into [OB₁₁H₁₂]^? by Fe³⁺ and oxygen. The radical anions [B₁₂H₁₂] ^{˙ ?} and [B₁₁H₁₁] ^{˙ ?} are assumed to be the primary products of the oxidation with the one‐electron oxidants Ag²⁺ and Fe³⁺, respectively. These radical anions are subsequently transformed into [OB₁₁H₁₂]^? by oxygen. The crystal structure analysis shows that the structure of [OB₁₁H₁₂]^? is derived from the hypothetical closo‐oxaborane OB₁₂H₁₂ by removal of the B3 vertex, leaving a non‐planar pentagonal aperture with a three‐coordinate O vertex, as predicted by NMR spectra and theory.     

[1‐Me‐1‐closo‐SnB11H11]− as a potential weakly coordinating anion: Synthesis of Rh(PPh3)2(1‐Me‐closo‐SnB11H11) and comparisons with Rh(PR3)2 (1‐H‐closo‐CB11 H11)

The closo‐stannaborane salt [Rh(PPh₃)₂‐(nbd)][1‐Me‐1‐closo‐SnB₁₁H₁₁] reacts with H₂ in CH₂ Cl₂ solution to afford the contact ion‐pair Rh(PPh₃)₂(1‐Me‐closo‐SnB₁₁H₁₁), which has been characterized in solution and the solid state by X‐ray diffraction. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:174–180, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20218     

2,2′‐Bi(9,9‐di­hexyl­fluorene)

The central part of the title mol­ecule, C₅₀H₆₆, is planar, all the rings being in the same plane; the lateral chains are also planar (excluding H atoms), almost perpendicular to the ring plane and grafted on the same side of the mol­ecule. The mol­ecule has nearly a mirror plane, perpendicular to the central C—C bond, instead of the centre of symmetry expected. The orientation of the plane of the rings is approximately 45° from the unit‐cell b axis, so that neighbouring mol­ecules are essentially perpendicular.     

Bi5O7Br and its structural relation to α‐Bi5O7I

Pentabismuth heptoxide bromide, Bi₅O₇Br, crystallizes in the space group Cmca. Its structure is compared with the closely related Ibca structure of α‐Bi₅O₇I. The change in the space group is assumedly the result of a compromise between the different spatial needs of Br and I and the rigidity of the {³_∞}[Bi, O] frameworks into which they are embedded. A detailed procedure for the synthesis of Bi₅O₇Br is given.