The crystal structures of the 1-methyl-3,4-benzo-1-telluracyclopentane and 1-phenyl-1-telluracyclopentane cations in their tetraphenylborate salts,C8H8TeMe+ BPh4− and C4H8TePh+ BPh4−

The crystal structures of C₈H₈TeMe⁺ BPh₄^? (I) and C₄H₈TePh⁺ BPh₄^? (II) have been determined from three-dimensional X-ray counter data.I is monoclinic, space group P2₁/n with a 9.175(1), b 17.402(3), c 16.998(3) Å, β 98.92(6)°, Z = 4, R = 5.1% for 1641 observed reflections.II is triclinic, space group P$\text{1}$ with a 9.635(3), b 17.721(3), c 16.858(8) Å, α 89.77(2), β 104.36(4), γ 90.16(2)°, Z = 4, R = 9.0% for 6466 observed reflections.In both I and II tellurium is three-coordinate in a pyramidal geometry, with TeC distances in the range 2.07(1)–2.14(1) Å (I) and 2.10(1)–2.17(1) Å (II). In both structures short contacts of 3.4—3.5 Å occur between tellurium and carbon atoms of the tetraphenylborate anion.     

The absolute configuration of the palmarumycins C9, C10, and C12 by quantum-mechanical calculations of CD spectra

The absolute configurations of the palmarumycins C₉ 1a, C₁₀ 2, and C₁₂ 3 were assigned by comparison of the quantum-mechanically calculated with the experimental CD spectra as (2R,3S,4aS,8aR), (2R,3R,4S,4aS,8aR), and (2R,3R,4R), respectively.     

The crystal structures of 1-allyl-1-bromo-3,4-benzo-1-telluracyclopentane [C8H8Te(C3H5)Br], 1-phenacyl-1-bromo-3,4-benzo-1-telluracyclopentane [C8H8Te(C8H7O)Br] and 1-deuteromethyl-1-iodo-3,4-benzo-1-telluracyclopentane [C8H8Te(CD3)I]; the trans effect in organotellurium bromides and iodides

The crystal structures of the title compounds have been determined from three-dimensional X-ray counter data.C₈H₈Te(CH₂CHCH₂)Br (I) is orthorhombic, space group Pbca with a 9.642(1), b 25.586(7), c 9.680(3) Å, Z = 8. The structure has been refined to R 5.2% for 1262 observed reflections.C₈H₈Te(CH₂COPh)Br (II) is orthorhombic, space group Pccn with a 23.593(6), b 14.337(3), c 9.180(2) Å, Z = 8. R = 5.5% for 1374 reflections.C₈H₈Te(CD₃)I (III) is orthorhombic, space group Pbca with a 11.200(3), b 15.976(2), c 23.328(3) Å, Z = 16. R = 5.6% for 2142 reflections.In I and II, tellurium is coordinated in an approximately octahedral geometry by the organic residues and three halogen contacts, with TeC and TeBr distances in the ranges 2.14(1)–2.19(1) Å and 3.328(2)–3.368(2) Å in (I) and 2.12(1)–2.18(1) Å and 3.292(2)–3.391(2) Å in II.In III, each of the two crystallographically independent complexes has tellurium coordinated in a distorted octahedral geometry. The TeC bond lengths are 2.10(2)–2.16(2) Å. In each case two TeI distances are in the range 3.596(2)–3.688(2) Å and a third, longer interaction (3.870(2) and 4.112(2) Å) completes the coordination.In each of the structures I–III the three covalent TeC bonds are oriented cis within the octahedra and exert a trans bond-lengthening effect on the Tehalogen interactions, precluding covalent-type bonding; the structures are essentially ionic, (C₈H₈TeR)⁺ cations and halide anions forming extended arrays.     

The crystal and molecular structure of ortho-terphenylenemercury dimer, (C18H12Hg)2

C₃₆H₂₄Hg₂, hexabenzo[b,d,f,i,k,m][1,8] dimercuracyclotetradecene, M_r = 857.768, monoclinic, P2₁/n, a 17.315(3), b 16.576(2), c 10.545(6) Å, β 114.60(4)°, U 2751.65 ų, Z = 4, D_m 2.055, D_x 2.071 g cm⁻³, λ(Mo-K_α) 0.71069 Å, μ 107.51 cm⁻¹, F(000) = 1600, T 293 K; Final R = 0.041 for 4290 observed reflections with I > 3σ(I). The two CHgC angles are 175.5(3) and 175.6(4)°; average CHg distance, 2.088(13) Å.     

Carbon-nitrogen bond formation in the reaction of the reaction of diphenyl diazomethane Ph2 CN2 with diiron-carbene complexes (Fe2(CO)7x03BD;-C(R)C(NEt2)x03BD;-C(R)C(NEtx03BC;-C(R)C(NEt2)N(NCPh2)x03BC;-C(R)C(NEtx03BC;-C(R)C(NEt2)NN(CPh2)x03BC;-C(R)C(NEt)]

The diiron ynamine complex [Fe₂(CO)₇{μ-CR)C(NEt₂)}] (1:R=Me,2:R = C₃H₅.3:R=SiMe₃.4:R = Ph) reacts at room temperature with diphenyldiazomethane Ph₂CN₂, in hexane to yield complexes [Fe₂(CO)₆{C(R)C(NEt₂)N (NCPh₂)] (5a:R=Me,6a:R=C₃H₅.7a R=SiMe₃.8a:R=Ph) resulting from the insertion of the terminal nitrogen atom into the Fe=C carbene bond. Insertion the second nitrogen atom and formation of compounds [Fe₂(CO)₆zμ-C(R)C(NEt₂)NN(CPh₂)}] (5b:R=Me,6b:R=C₃H₅,7b:R=SiMe₃,8b:R=Ph) is observed when compounds5a-5a are treated in refluxing hexane. Transformation of compoundsa tob is also obtained at room temperature within a few days. All compounds were identified by their¹H NMR spectra. Compounds6a, 7a, 8a, and8b were characterized by single crystal X-ray diffraction analyses. Crystal data: for6a: space group = P2₁/n,a=12.853(1) A,b=24.800(7) A,c=8.947(6) A,β=99.29(3)°,Z=4, 2227 rellectionsR=0,038; for7a: space group=Pl,a=ll.483(4) A,b=14.975(4) A,c = 17.890(8) A,α = 82.80(3)°,β=94.29(7)°,γ=85.42(2),Z = 4, 5888 reflectionR = 0.035: for8a: space group = Pcab.a = 31.023(8) A.b=20.137(1) A.c=9.686(2) A.Z=8. 1651 reflections,R=0.071; for8b: space group=P2₁/n,a=21.459(4),b=10,100(3) A,c=28,439(8) A,ß=103.86(4)°,Z=8. 2431 reflections.R=0.057.     

Reaction of MeO2C(H)C=C=C(H)CO2Me with Ru3(CO)12. New diruthenium complexes with bridging carboxylate-substituted allene ligands

The reaction of Ru₃(CO)₁₂ with MeO₂C(H)C=C=C(H)CO₂ Me has yielded two isomeric productsanti-Ru₂(CO)₆[μ-η ³-η ¹-MeO₂C(H)CCC(H)CO₂Me],1 in 70% yield andsyn-Ru₂(CO)₆[μ-η ³-η ¹-MeO₂C(H)CCC(H)CO₂Me],2 in 5% yield. Both compounds were characterized by single crystal X-ray diffraction analysis. Both products are diruthenium complexes with bridging di(carboxylate)allene ligands in which the oxygen atom of the carbonyl group of one of the carboxylate groupings is coordinated to one of the metal atoms. Compound1 isomerizes partially to2 at 68°C. Crystal Data for1: space group=P2₁/n,a=11.131(1) Å,b=10.228(2) Å,c=15.978(2) Å,β=102.01(1)°,Z=4, 1653 reflections,R=0.025; for2: space group=P $\bar 1$ ,a=9.340(1) Å,b=14.925(4) Å,c=6.778(2) Å,α=99-02(2)°,β=104 62(2)°,γ=94.58(2)°,Z=2, 1857 reflections,R=0.027.     

Synthesis of enantiomerically pure spiro-cyclopropane derivatives containing multichiral centers

A novel chiral source, 5-(R)-[(1R,2S,5R)-(−)-menthyloxy]-3-bromo-2(5H)-furanone (5a), was obtained in 46% yield with d.e.≥98% from the epimeric mixture of 5-(l-menthyloxy)-3-bromo-2(5H)-furanone (5a+5b) obtained via the bromination of an epimeric mixture of 5-(l-menthyloxy)-2(5H)-furanone (3a+3b) followed by the elimination of hydrogen bromide. The asymmetric reaction of 5a with a nucleophilic alcohol afforded enantiomerically pure spiro-cyclopropane derivatives containing four stereogenic centers, 9a–9e, in 50–68% yield with d.e.≥98%. The enantiomerically pure compounds 9a–9e were identified on the basis of their analytical data and spectroscopic data, such as [α]_D²⁰, UV, IR, ¹H NMR, ¹³C NMR, MS and elementary analysis. The absolute configuration of the chiral spiro-cyclopropane compound 9a was established by X-ray crystallography.     

The use of crown ethers to access new M[Al2R6X] species. Synthesis and crystal structure of [K · dibenzo-18-crown-6] [Al2Me6Cl] · 2 C6H6

Potassium chloride does not react with trimethylaluminium in benzene in the absence of a crown ether. With the addition of dibenzo-18-crown-6, a normal liquid clathrate ensues. The composition of the parent compound has been established by a single crystal X-ray diffraction study. The space group is monoclinicP2₁/c with unit cell dimensionsa=21.319(8),b=9.512(4),c=21.081(8) Å, β=93.79(3)°, andρ _calc1.15 g cm^?3 forZ=4. Refinement led to a final conventionalR value of 0.049 for 2224 observed reflections. The anion has the expected angular geometry (Al?Cl?Al=120.0(1)°). There are two different types of benzene in the crystalline solid. One is associated with the K⁺ ion, while the other exists in layers normal to thea axis.     

LiB3O5 crystal structure at 20, 227 and 377 °C

Crystal structure of LiB₃O₅ (a framework of [B₃O₅]⁻ rings and Li atoms located in interspaces) was refined at high temperatures using single-crystal X-ray diffraction, MoKα-radiation, anharmonic approximation, orthorhombic; Pna2₁; Z=4; 20 °C (a=8.444, b=7.378, c=5.146 Å, 1411 F(hkl), R=0.022); 227 °C (a=8.616, b=7.433, c=5.063 Å, 1336 F(hkl), R=0.026), 377 °C (a=8.746, b=7.480, c=5.013 Å, 1193 F(hkl), R=0.035). A high mobility of Li atoms and their highly asymmetric vibrations are revealed. Ellipsoid of Li thermal vibrations is oviform. Li is shifted on heating to 0.26 Å mainly along a-axis causing high thermal expansion in this direction; Li temperature factors are multiplied by 4 on heating. Rigid boron-oxygen groups in LiB₃O₅ remain practically stable on heating similar to α-Na₂B₈O₁₃ and α-CsB₅O₈. At the same time these groups rotate relative to each other like hinges leading to extremely anisotropic thermal expansion (α_a=101, α_b=31, α_c=−71, α_v=60×10⁻⁶ °C⁻¹, 20-530 °C, HTXRPD data).     

The effect of anions on hydrogen chemisorption and oxide formation on Pt in aqueous acids

An approximate treatment shows that the superficial area of a mercury pool overlain by an aqueous electrolyte solution and contained within a cylindrical vessel of radius R (not less than about 12 mm) is given by πR²+2.603 aR+0.26 a², where a is a constant in the range 2.4±0.2 mm.     

The orbital description of the potential energy curves and properties of the lower excited states of the BH molecule

The electronic wavefunctions for the ground (X¹ Σ⁺) and the low-lying excited states (a³Π, A¹Π, ³Σ⁺) of the BH molecule have been calculated as a function of internuclear distance using the ab initio generalized valence bond method (GVB) with optimization of spin coupling (SOGI). The potential curve of the A¹Π state in the zero rotational level is found to have a hump of 0.150 eV at R = 3.8₉a_o (experimentally a hump of unknown size is found at 3.9 ± 0.4 a₀); a smaller hump at larger R (0.02 eV at R = 4.9₂a₀) is also found for the calculated a³Π state. The presence of such humps is found to result from the recoupling of orbitals that must occur as R is decreased from ∞ to R_e and is comparable in origin to the activation barrier in a radical exchange reaction (e.g., H₂ + D ? HD + H). The calculated binding energies of the BH states are 3.272 eV (X¹ Σ⁺), 2.216 eV (a³ Π), and 0.502 eV (A¹ Π). The ³Σ⁺ state is unbound although it does exhibit a small unbound minimum. The dipole moment, quadrupole moment, and electric field gradient are calculated as a funtion of R. The shapes of the potential curves and the properties are interpreted in terms of simple qualitative considerations of the GVB orbitals.     

Lithium ion insertion and extraction reactions with Hollandite-type manganese dioxide free from any stabilizing cations in its tunnel cavity

Lithium ion insertion and extraction reactions with a hollandite-type α-MnO₂ specimen free from any stabilizing cations in its tunnel cavity were investigated, and the crystal structure of a Li⁺-inserted α-MnO₂ specimen was analyzed by Rietveld refinement and whole-pattern fitting based on the maximum-entropy method (MEM). The pH titration curve of the α-MnO₂ specimen displayed a monobasic acid behavior toward Li⁺, and an ion-exchange capacity of 3.25 meq/g was achieved at pH>11. The Li/Mn molar ratio of the Li⁺-inserted α-MnO₂ specimen showed that about two Li⁺ ions can be chemically inserted into one unit cell of the hollandite-type structure. As the amount of Li content was increased, the lattice parameter a increased while c hardly changed. On the other hand, the mean oxidation number of Mn decreased slightly regardless of Li content whenever ions were exchanged. The Li⁺-inserted α-MnO₂ specimen reduced topotactically in one phase when it was used as an active cathode material in a liquid organic electrolyte (1:1 EC:DMC, 1 mol/dm³ LiPF₆) lithium cell. An initial discharge with a capacity of approximately 230 mAh/g was achieved, and the reaction was reversible, whereas the capacity fell steadily upon cycling. About six Li⁺ ions could be electrochemically inserted into one unit cell of the hollandite-type structure. By contrast, the parent α-MnO₂ specimen showed a poor discharge property although no cationic residues or residual H₂O molecules remained in the tunnel space. Rietveld refinement from X-ray powder diffraction data for a Li⁺-inserted specimen of (Li₂O)_0.12MnO₂ showed it to have the hollandite-type structure (tetragonal; space group I4/m; a=9.993(11) and ; Z=8; R_wp=6.12%, R_p=4.51%, R_B=1.41%, and R_F=0.79%; S=1.69). The electron-density distribution images in (Li₂O)_0.12MnO₂ showed that Li₂O molecules almost fill the tunnel space. These findings suggest that the presence of stabilizing atoms or molecules within the tunnel of a hollandite-type structure is necessary to facilitate the diffusion of Li⁺ ions during cycling.     

Phenylmercury dithiolates. The crystal and molecular structures of (C6H5Hg(S2COR) (R = Me; iPr and (C6H5)Hg(S2CNEt2))

The preparation, spectroscopic characterization, and X-ray structures of a number of phenylmercury dithiolates (xanthate and dithiocarbamate) are reported. The solid state structures feature monodentate dithiolate ligands and approximate linear geometries about the mercury atoms. The HgS distances fall within the relatively narrow range of 2.374(4)–2.388(2) Å in these compounds. The presence of additional Hg ⋯ S contacts also characterize these structures; the number and strength of these interactions depending on the nature of the dithiolate ligand. Crystals of PhHg(S₂COMe) are monoclinic, space group C2/c with unit cell dimensions a 37.73(2), b 4.825(1), c 12.686(1) Å, β 101.21(2)° with Z = 8; PhHg(S₂COⁱPr) crystallizes in the monoclinic space group P2₁/a with a 13.678(5), b 21.347(7), c 14.570(6) Å, β 114.99(2)° and Z = 12; and crystals of PhHg(S₂CNEt₂) are triclinic, P1, with cell parameters a 9.959(2), b 12.359(4), c 13.098(2) Å, α 65.53(2), β 65.81(2), γ 81.26(2)° and Z = 4. Refinement on 777 reflections [with I ≥ 3.0σ(I)] converged with final R 0.096 and R_w 0.090 for PhHg(S₂COMe); 2888 reflections [I ≥ 2.5 σ(I)], R 0.033, R_w 0.038 for PhHg(S₂COⁱPr); 2675 reflections [I ≤ 2.5 σ (I)], R, 0.033, R_w 0.038 for PhHg(S₂CNEt₂).     

Non-enzymatic diastereoselective asymmetric desymmetrization of 2-benzylserinols giving optically active 4-benzyl-4-hydroxymethyl-2-oxazolidinones: asymmetric syntheses of α-(hydroxymethyl)phenylalanine,N-Boc-α-methylphenylalanine,cericlamine and BIRT-377

A reaction of (S)-2-benzyl-2-(α-methylbenzyl)amino-1,3-propanediol (S)-4a and 2-chloroethyl chloroformate, and the subsequent addition of DBU gave (4R,αS)-4-benzyl-4-hydroxymethyl-3-(α-methylbenzyl)-2-oxazolidinone (4R)-5a (92% de) via a diastereoselective asymmetric desymmetrization process. Debenzylation of (4R)-5a using trifluoromethanesulfonic acid and anisole in MeNO₂ gave (R)-4-benzyl-4-hydroxymethyl-2-oxazolidinone (R)-15a, which was converted into (R)-(α-hydroxymethyl)phenylalanine (7) in two steps. N-Boc-α-methylphenylalanine (8), cericlami0ne (9) and BIRT-377 (10) were also synthesized using these asymmetric desymmetrization and debenzylation.     

Unimolecular reactions of the isolated immonium ions CH3CH = NH+C4H9, CH3CH2Ch = NH+C4H9 and (CH3)2C = NH+C4H9

The reactions of ten metastable immonium ions of general structure R¹R²C?NH⁺C₄H₉ (R¹ = H, R² = CH₃, C₂H₅; R¹ = R² = CH₃) are reported and discussed. Elimination of C₄H₈ is usually the dominant fragmentation pathway. This process gives rise to a Gaussian metastable peak; it is interpreted in terms of a mechanism involving ion-neutral complexes containing incipient butyl) cations. Metastable immonium ions ontaining an isobutyl group are unique in undergoing a minor amount of imine (R¹R²C?NH) loss. This decomposition route, which also produces a Gaussian metastable peak, decreases in importance as the basicity of the imine increases. The correlation between imine loss and the presence of an isobutyl group is rationalized by the rearrangement of the appropriate ion-neutral complexes in which there are isobutyl cations to the isomeric complexes containing the thermodynamically more stable tert-butyl cations. A sizeable amount of a third reaction, expulsion of C₃H₆, is observed for metastable n-C₄H₉ ⁺NH?CR¹R² ions; in contrast to C₄H₈ and R¹R²C?NH loss, C₃H₆ elimination occurs with a large kinetic energy release (40–48 kJ mol^?1) and is evidenced by a dish-topped metastable peak. This process is explained using a two-step mechanism involving a 1,5-hydride shift, followed by cleavage of the resultant secondary open-chain cations, CH₃CH⁺ CH₂CH₂NHCHR¹R².     

Stereoselective synthesis of cationic heterobidentate C(NHC)/SR rhodium(I) complexes using stereodirecting N,N-dialkylamino groups

The synthesis of two different types of chiral C/S ligands based upon N-(N,N-dialkylamino)-substituted N-heterocyclic carbenes and thioether functionalities, along with their neutral [RhCl(CNH)(COD)] and cationic [Rh(I)(NHC/S)(COD)]⁺ complexes, has been accomplished. (S)-2-[(Phenylthio)methyl]pyrrolidine, carrying the thioether moiety, and (2S,5S)-2,5-diphenylpyrrolidine, combined with a thioether functionalized side chain, were studied as potential stereodirecting groups. Only the latter provided high selectivity in the formation of the neutral complex, leading to a single atropoisomer (de >98%) of the newly formed, configurationally stable C(NHC)–Rh bond. The synthesis of the corresponding cationic [Rh(I)(NHC/S)(COD)]⁺ complexes, however, resulted in the formation of single (R_a,S_S) and (S_a,S_S) diastereomers, respectively, of the four possible complexes in each case [combinations of the (R_a/S_a) C(NHC)–Rh axis and the (S_s/R_s) stereogenic S center formed upon coordination]. For the proline derivative, the resolution of the mixture of (R_a/S_a)-[RhCl(CNH)(COD)] neutral complexes proceeds via dynamic kinetic resolution through coordinatively unsaturated Rh(I) intermediates formed after halide abstraction. The absolute configurations of both types of cationic complexes were unequivocally assigned on the basis of X-ray diffraction analysis.     

Etude structurale de la forme ordonnée de LiAl5O8

A single crystal of ordered LiAl₅O₈ has been prepared by image furnace melting and its structure has been determined; 400 X-ray reflections were collected on an automatic counter diffractometer (MoKα radiation). The structure is of the spinel type. The space group is P4₃32 (or P4₁32); the lattice parameter is a = 7.908(2), Å, Z = 4. The value of R is 0.022. The distribution of cations shows the absence of Li⁺ ions in tetrahedral cation sites and 1–3 imperfect ordering of Li⁺ and Al₃₊ in octahedral cation sites of spinel.     

Structure of [C3H5O]+ ions produced from unimolecular decomposition of several [C4H8O]+˙ metastable ions

It is demonstrated by means of collisionally activated decomposition (CAD) that [C₃H₅O]⁺ originating from metastable [C₄H₈O]^+˙ ions are either acylium [C₂H₅CO]⁺ (a) or hydroxycarbenium [CH₂CHCHOH]⁺ (b). Butanone gives exclusively a but 2-methyl-2-propen-1-ol, 2-buten-1-ol, 3-buten-1-ol, butanal and 2-methylpropanal lead to ion b. Both structures a and b are produced from 3-buten-2-ol. These results are discussed in conjunction with experimental and calculated (MINDO/3) thermodynamic data.     

Synthesis and crystal structure of (2.2.2-cryptand)potassium perchlorate

A new complex (2.2.2-cryptand)potassium perchlorate [K(Crypt-222)]ClO₄ is synthesized, and its structure is studied by X-ray diffraction analysis (space group R32, a = 8.441 Å, c = 30.475 Å, Z = 3). The structure is solved by the direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.032 for 1222 independent (with allowance for anomalous dispersion) reflections (CAD4 automated diffractometer, λMoK _α radiation). The centers of the ClO ₄ ^? anion and [K(Crypt-222)]⁺ complex cation are in the positions (0,0,0) and (0,0,1/2), respectively, with the point symmetry 32. The ClO ₄ ^? anion is randomly disordered. The complex cation (with the high symmetry D ₃) is of the host-guest type and is somewhat disordered and exists as two different conformations with probabilities of 87 and 13%. The coordination polyhedron of the K⁺ cation (coordination number 8) is a two-base-centered trigonal prism distorted toward antiprism.     

A convenient procedure for the synthesis of chiral 6,7-dihydroxy-1-phenylamino-dihydro-1H-pyrrolo[1,2-a]imidazole-2,5(3H,6H)-diones

The cyclocondensation reactions between l-α-amino acid phenylhydrazides and 2,3-O-isopropylidene-l-erythruronolactone in the presence of a catalytic amount of p-toluenesulfonic acid afforded diastereomerically pure (3S,6R,7R,7aS)-3-substituted-6,7-isopropylidenedioxy-1-phenylamino-dihydro-1H-pyrrolo[1,2-a]imidazole-2,5(3H,6H)-diones, which were converted by acidic hydrolysis with MeOH–HCl into their corresponding optically active (3S,6R,7R,7aS)-3-substituted-6,7-dihydroxy-1-phenylamino-dihydro-1H-pyrrolo[1,2-a]imidazole-2,5(3H,6H)-diones in good yields.