Kinetics of Depletion of Electronically Excited Ti Atom by CH4, C2H2, C2H4 and C2H6

The kinetics of depletion of ground state Ti(a³F) and electronically excited state Ti(a⁵F) upon interactions with CH₄, C₂H₂, C₂H₄, and C₂H₆ are studied in a fast-flow reactor at a He pressure of 0.70 Torr. No depletion of ground state Ti(a³F) was observed upon interaction with all hydrocarbons studied here. Two alkanes, CH₄ and C₂H₆, were also quite inert for depletion of the excited state Ti(a⁵F), On the other hand, C₂H₂ and C₂H₄ deplete the excited state Ti(a⁵F) very efficiently. Rate constants were determined to be (266 ± 86) and (476 ± 88) × 10^?12 cm³s^?1 for Ti(a⁵F) + C₂H₄ and Ti(a⁵F) + C₂H₂, respectively. These large rate constants compared with the ground state Ti were explained by an electron donor-acceptor interaction model that works in the interaction between C₂H₄ or C₂H₂ and the excited state with unfilled 4s orbital.     

The Analysis of Gentamicin Sulphate in Pharmaceutical Specialities by High Performance Liquid Chromatography

Abstract

This paper describes an H.P.L.C. method for the assay of gentamicin sulphate, utilising pre-column derivatisation with an ophthalaldehyde/thioglycollic acid reagent, ion-paired chromatography of the derivative on a Hypersil O.D.S. column and U.V. detection. The four major components of gentamicin are resolved (Gentamicins C₁, C_1a, C₂ and C_2a) and evidence is presented to show that the method is stability indicating. The application of this technique to formulated products is described and figures for precision and accuracy as well as stability results are given.     

Total synthesis of maremycins A,B, C1/C2, D1, and D2

The total synthesis of maremycins A, B, C₁/C₂, D₁, and D₂ is achieved starting from the natural amino acids l-isoleucine and S-methyl-l-cysteine, in which the total synthesis of maremycins B, C₁/C₂, and D₂ is accomplished for the first time. The synthesis features a position-selective intramolecular bromination process for the synthesis of key chiral building block, a Pd-catalyzed indole synthesis for the preparation of (2S,3S)-β-methyltryptophan and hydroxylation of oxindoles by molecular oxygen. In addition, the protocol for conversion of maremycins A and B to maremycins C and D was improved.     

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.     

State‐state transitions for CCl2(X1A1, A1B1, a3B1) radical and collisional quenching of CCl2(A1B1 and a3B1) by O2, N2, NO,N2O,NH3, and various aminated molecules

CCl₂ free radicals were produced by a pulsed dc discharge of CCl₄ in Ar. Ground electronic state CCl₂(X) radicals were electronically excited to the A¹B₁ (0,4,0) vibronic state with an Nd:YAG laser pumped dye laser at 541.52 nm. Experimental quenching data of excited CCl₂(A¹B₁ and a³B₁) by O₂, N₂, NO, N₂O, NH₃, NH(CH₃)₂, NH(C₂H₅)₂, and N(C₂H₅)₃ molecules were obtained by observing the time‐resolved total fluorescence signal of the excited CCl₂ radical in a cell, which showed a superposition of two exponential decay components under the presence of quencher. The quenching rate constants k_A of CCl₂(A) state and k_a of CCl₂(a) state were derived by analyzing the experimental data according to a proposed three‐level model to deal with the CCl₂(X¹A₁, A¹B₁, a³B₁) system. The formation cross sections of complexes of electronically excited CCl₂ radicals with O₂, N₂, NO, N₂O, NH₃, and aminated molecules were calculated by means of a collision‐complex model. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 351–356, 2002     

Seltenerdhalogenide Ln4X5Z. Teil 1: C und/oder C2 in Ln4X5Z

Rare Earth Halides Ln₄X₅Z. Part 1: C and/or C₂ in Ln₄X₅Z The compounds Ln₄X₅C_n (Ln = La, Ce, Pr; X = Br, I and 1.0 < n < 2.0) are prepared by the reaction of LnX₃, Ln metal and graphite in sealed Ta‐ampoules at temperatures 850 °C < T < 1050 °C. They crystallize in the monoclinic space group C2/m. La₄I₅C_1.5: a = 19.849(4) Å, b = 4.1410(8) Å, c = 8.956(2) Å, β = 103.86(3)°, La₄I₅C_2.0: a = 19.907(4) Å, b = 4.1482(8) Å, c = 8.963(2) Å, β = 104.36(3)°, Ce₄Br₅C_1.0: a = 18.306(5) Å, b = 3.9735(6) Å, c = 8.378(2) Å, β=104.91(2)°, Ce₄Br₅C_1.5: a = 18.996(2) Å, b = 3.9310(3) Å, c = 8.282(7) Å, β = 106.74(1)°, Pr₄Br₅C_1.3: a = 18.467(2) Å, b = 3.911(1) Å, c = 8.258(7) Å, β = 105.25(1)° and Pr₄Br₅C_1.5: a = 19.044(2) Å, b = 3.9368(1) Å, c = 8.254(7) Å, β = 106.48(1)°. In the crystal structure the lanthanide metals are connected to Ln₆‐octahedra centered by carbon atoms or C₂‐groups. The Ln₆‐octahedra are condensed via opposite edges to chains and surrounded by X atoms which interconnect the chains. A part n of isolated C‐atoms is substituted by 1‐n C₂‐groups. The C‐C distances range between 1.26 and 1.40Å. In the ionic formulation (Ln³⁺)₄(X^?)₅(C^4?)_n(C₂^m?)_1?n·e^? with 0 < n < 1 and m = 2, 4, 6 (C₂^2?, C₂^4? C₂^6?), there are 1 < e^? < 5 electrons centered in metal‐metal bonds.     

Pr6C2‐Doppeltetraeder in Pr6C2Cl10 und Pr6C2Cl5Br5

Pr₆C₂‐Bitetrahedra in Pr₆C₂Cl₁₀ and Pr₆C₂Cl₅Br₅ The compounds Pr₆C₂Cl₁₀ and Pr₆C₂Cl₅Br₅ are prepared by heating stoichiometric mixtures of Pr, PrCl₃, PrBr₃ and C in sealed Ta capsules at 810 ? 820 °C. They form bulky transparent yellow to green and moisture sensitive crystals which have different structures: space groups C2/c, (a = 13.687(3) Å, b = 8.638(2) Å, c = 15.690(3) Å, β = 97.67(3)° for Pr₆C₂Cl₁₀ and a = 13.689(1) Å, b = 10.383(1) Å, c = 14.089(1) Å, β = 106.49(1)° for Pr₆C₂Cl₅Br₅). Both crystal structures contain C‐centered Pr₆C₂ bitetrahedra, linked via halogen atoms above edges and corners in different ways. The site selective occupation of the halogen positions in Pr₆C₂Cl₅Br₅ is refined in a split model and analysed with the bond length‐bond strength formalism. The compound is further characterized via TEM investigations and magnetic measurements (μ_eff = 3.66 μ_B).     

Occurrence of the Unusual 2C5 (1C4) Chair Conformation in Two Carbohydrates and the Reverse Anomeric Effect. X-Ray Structures of 3,4,5,7-Tetra-O-Acetyl-2,6-Anhydro-D-Glycero-D-Ido-Heptonamide (1) and 3,4,5,7-Tetra-O-Acetyl-2,6-Anhydro-D-Glycero-L-Gluco-Heptonamide (2)

Abstract

The title compounds 1 and 2 (both C₁₅O₁₅NH₂₁) crystallized in the monoclinic space group P2₁ (Z = 2) with a=8.864(1), b=8.346(1), c =13.569(1)Å, β =114.12(1), V=918.1(2)A3, D(calc) = 1.358 g/cc for compound 1, and a=15–045(1), b=8.106(1), c=7.491(1)Å, β =97.23(1)°, V=906.4(3)Å3 D(calc)= 1.375 g/cc, for compound 2. The structures were solved by direct methods and refined by the full-matrix least squares technique to R indices of 0.010 and 0.046, respectively. Both compounds are in the α ? D configuration and adopt the unusual ²C₅, (¹C₄) chair conformation with the carbamoyl groups on the anomeric carbon atoms equatorially oriented. In this conformation the orientations of the substituents are 2e, 3a, 4a, 5a and 6a in 1 and 2e, 3a, 4a, 5e and 6a in 2 which leads to unfavorable 1,3-diaxial interactions. The “reverse anomeric effect” which induces the ²c₅ chair conformation in these compounds, may have its origin in the unfavorable steric interactions found in the ⁵c₂ (⁴C₁) conformation where the carbamoyl group is axially oriented. Furthermore, the ²C₅ conformation is stabilized by the N-H … O intramolecular hydrogen bond between the carbamoyl nitrogen atom and the pyranosyl ring oxygen atom. Semi-empirical energy calculations reveal that the rotational freedom of the carbamoyl group is greater for the equatorial orientation (²C₅) than for the axial orientation (⁵C₂).     

Das erste Bromid mit trigonal-bipyramidalen [M5(C2)]-Clustern: [Pr5(C2)]Br9

The First Bromide with Trigonal-Bipyramidal [M₅(C₂)] Clusters: [Pr₅(C₂)]Br₉ The bromide [Pr₅(C₂)]Br₉ is obtained via metallothermic reduction of PrBr₃ with rubidium in the presence of praseodymium and carbon in a sealed niobium container at 730°C as dark red single crystals. [Pr₅(C₂)]Br₉ crystallizes in the monoclinic crystal system [P2₁/n; Z = 4; a = 1 006.9(1); b = 1 886.1(1); c = 1 045.9(1) pm; β = 108.130(1)°; R_int = 0.059; R1 = 0.038; wR2 = 0.077]. One edge in the base of the trigonal bipyramid in [Pr₅(C₂)]Br₉ is usually long (440 pm). It is not brigded by a Brⁱ ligand. In addition to the eight Brⁱ, the cluster is coordinated by 12 terminal ligands (Br^a). Except for the known Br^a–a–a and Br^i–a connections, Br^i–a–a brigdes are observed for the first time for trigonal-bipyramidal clusters.     

Quantitative fluorometric in-situ determination of netilmicin and 4 gentamicins on TLC-RP-layers

Summary This investigation describes a thin-layer chromatographic method for the quantitative determination of netilmicin and gentamicins C₁, C_1a, C₂ and C_2a in pharmaceutical preparations. The individual components are separated on C₈ or C₁₈ reversed phase layers with a mobile phase consisting of methanol and ammonia with added lithium chloride. After optimization of the post-chromatographic derivatization with 2,2-diphenyl-1-oxa-3-oxonia-2-boratanaphthalene (DOOB) quantitative determination takes place directly on the layer. The calibration curves are linear for netilmicin in the range 50–250 ng/zone and for the gentamicin components in the range 30–140 ng/zone (this corresponds to 100 to 400 ng/zone total complex). The determination limits per zone are 50 ng total gentamicin complex and 10 ng netilmicin per zone. No clean-up is required for analysis because of the great specificity of the derivatization reaction. The reproducibility of the method for independently carried out measurement series can be described by coefficients of variation between CV = ±1.7%–4.2%.

---

Quantitative fluorometrische in situ-Bestimmung von Netilmicin und 4 Gentamicinen auf DC-RP-Schichten

---

Teilergebnis der Dissertation von F. R. Kunz     

Darstellung und Charakterisierung der Fulleren-Kokristallisate C60 · 12 C6H12, C70 · 12 C6H12, C60 · 12 CCl4, C60 · 2 CHBr3, C60 · 2 CHCl3, C60 · 2 H2CCl2

Synthesis and Characterization of the Fullerene Co-Crystals C₆₀ · 12 C₆H₁₂, C₇₀ · 12 C₆H₁₂, C₆₀ · 12 CCl₄, C₆₀ · 2CHBr₃, C₆₀ · 2CHCl₃, C₆₀ · 2H₂CCl₂ By crystallization of fullerenes from non-polar solvents (C₆H₁₂, CCl₄, CHBr₃, CHCl₃, H₂CCl₂) compounds of the following compositions were obtained: C₆₀ · 12C₆H₁₂, C₇₀ · 12C₆H₁₂, C₆₀ · 12CCl₄, C₆₀ · 2CHCl₃, C₆₀ · 2CHBr₃ and C₆₀ · 2H₂CCl₂. Lattice parameters have been determined by X-ray diffraction of powder samples; according to single-crystal examinations on C₆₀ · 12C₆H₁₂, C₆₀ · 12CCl₄ and C₆₀ · 2CHBr₃ the fullerene is orientationally disordered. C₆₀ · 12C₆H₁₂, cubic, a = 28.167(1) Å; C₇₀ · 12C₆H₁₂, cubic, a = 28.608(2) Å; C₆₀ · 12CCl₄, cubic, a = 27.42(1) Å; C₆₀ · 2CHBr₃, hexagonal, a = 10.212(1), c = 10.209(1) Å; C₆₀ · 2CHCl₃, hexagonal, a = 10.08(1), c = 10.11(2) Å; C₆₀ · 2H₂CCl₂, tetragonal, a = 16.400(1) Å, c = 11.645(7) Å.     

Rate constants for the elementary reactions between CN radicals and CH4, C2H6, C2H4, C3H6, and C2H2 in the range: 295 ⩽ T/K ⩽ 700

Pulsed laser photolysis, time-resolved laser-induced fluorescence experiments have been carried out on the reactions of CN radicals with CH₄, C₂H₆, C₂H₄, C₃H₆, and C₂H₂. They have yielded rate constants for these five reactions at temperatures between 295 and 700 K. The data for the reactions with methane and ethane have been combined with other recent results and fitted to modified Arrhenius expressions, k(T) = A′(298) (T/298)ⁿ exp(?θ/T), yielding: for CH₄, A′(298) = 7.0 × 10^?13 cm³ molecule^?1 s^?1, n = 2.3, and θ = ?16 K; and for C₂H₆, A′(298) = 5.6 × 10^?12 cm³ molecule^?1 s^?1, n = 1.8, and θ = ?500 K. The rate constants for the reactions with C₂H₄, C₃H₆, and C₂H₂ all decrease monotonically with temperature and have been fitted to expressions of the form, k(T) = k(298) (T/298)ⁿ with k(298) = 2.5 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.24 for CN + C₂H₄; k(298) = 3.4 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.19 for CN + C₃H₆; and k(298) = 2.9 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.53 for CN + C₂H₂. These reactions almost certainly proceed via addition-elimination yielding an unsaturated cyanide and an H-atom. Our kinetic results for reactions of CN are compared with those for reactions of the same hydrocarbons with other simple free radical species. © John Wiley & Sons, Inc.     

Opening a New Series of Calcium Boridecarbides with Heterographene Nets by Ca1–x(B,C)6 and Ca1–x(B,C)8 – Two Members of the (CaB2)Cn Compound Series

Ca_1–xB₂C₄ (x ~ 0.08) and Ca_1–xB₂C₆ (x ~ 0.04) are two compounds containing heterographene‐B,C nets which were prepared by solid state synthesis and structurally characterized by X‐ray powder diffraction data. Both compounds crystallize in the space group P6/ mmm (No. 191). The lattice constants are a = 4.55971(5) Å and c = 4.4020(1) Å for CaB₂C₄ and a = 2.58390(5) Å, c = 4.43597(8) Å for CaB₂C₆. The calcium atoms are intercalated between the heterographene (B,C) nets. The calcium atom distribution in Ca_1–xB₂C₆ is disordered, leading to diffuse scattering. A model for this disorder was developed that matches well the observed diffuse scattering observed in the electron diffraction pattern. For Ca_1–xB₂C₆ and its decomposition products magnetic and electric properties are being reported.     

NC Palladacycles and C,C-chelating phosphorus ylide complexes: synthesis,X-ray characterization,and comparison of the catalytic activity in the Suzuki-Miyaura reaction

Six secondary amine palladacycles bearing monodentate ligands (1a, 2a), 1,2-bis(diphenylphosphino)ethane (dppe) and 1,3-bis(diphenylphosphino)propane (dppp) containing bridging and bidentate ligands (1b, 2b–d), and four C,C-type phosphorus ylide complexes containing thiourea (tu) (3a), phenyl isothiocyanate (4a), and bridging and terminal azide groups (5 and 5a) have been synthesized. Resulting complexes have been characterized by elemental analyses, IR, ¹H-, ¹³C{¹H}-, and ³¹P{¹H}-NMR spectroscopy with single crystal X-ray structure determination of 1a and 2a. The Pd in 1a and 2a occupies the center of a slightly distorted square planar environment formed by C_aryl, N_amine, N_pyridine, and Cl. The catalytic efficiency of complexes showed that in most cases, amine palladacycles display better catalytic activities than the phosphorus ylide Pd(II) complexes. Comparison between bidentate and bridging dppe complexes showed that dppe-bridged dimer 2d has higher catalytic activity than dppe bidentate complex.     

Crystal solvate of C60 with tricloroethylene,C60 · C2HCl3

Extraction of fullerenes from carbon soot by trichloroethylene has been studied. We have found that C₆₀ forms a solvate with trichloroethylene (C₆₀ · C₂HCl₃:a=31.31(1);b= 10.156(4);c=10.146(4) Å;V=3228.6 ų,Z=4,d _calc=1.752 g cm^–3, orthorhombic symmetry). Its thermal stability has been studied using TG and DSC. A phase transition of the first order at 167 K has been detected.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1248–1250, July, 1994.The authors are grateful to V. P. Bubnov and I. S. Krainskii for providing them with the samples of fulle-rene-containing carbon soot, and to M. G. Kaplunov and A. V. Zvarykina for assistance in the work.This work was carried out with the financial support of the Russian Foundation for Basic Research, Project Nos. 93-03-18705 and 93-03-5650.     

Cyclodimerization of 1-(Dimethoxyniethyl)-5,6-dimethylidene-7-oxa-bicyclo[2.2.1]hept-2-ene Induced by Nonacarbonyldiiron. Crystal Structure of (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)- Tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl)-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)]iron

The transition-metal-carbonyl-induced cyclodimerization of 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene is strongly affected by substitution at C(1) While 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept–2-ene-l-methanol ( 7 ) refused to undergo [4 + 2]-cyclodimerization in the presence of [Fe₂(CO)⁹] in MeOH, 1-(dimethoxymethyl)-5,6-di-methylidene-7-oxabicyclo[2.2.1]hept-2-ene ( 8 ) led to the formation of a 1.7:1 mixture of ‘trans’ ( 19, 21, 22 ) vs. ‘cis’ ( 20, 23, 24 ) products of cyclodimerization together with tricarbonyl[C, 5,6, C-η-(l-(dimethoxymethyl)-5,6-di-methylidenecyclohexa-1,3-diene)]iron ( 25 ) and tricarbonyl[C,3,4, C-η-(methyl 5-(dimethoxymethyl)-3,4-di-methylidenecyclohexa-1,5-diene-l-carboxylate)]iron ( 26 ). The structures of products 19 and of its exo ( 21 ) and endo ( 22 ) [Fe(CO)₃(1,3-diene)]complexes) and 20 (and of its exo ( 23 ) and endo (24) (Fe(CO)₃(1,3-diene)complexes) were confirmed by X-ray diffraction studies of crystalline (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)-tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl])-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)iron ( 21 ). In the latter, the Fe(CO)₃(1,3-diene) moiety deviates significantly from the usual local C_s symmetry. Complex 21 corresponds to a ‘frozen equilibrium’ of rotamers with η-alkyl, η³-allyl bonding mode due to the acetal unit at the bridgehead centre C(1).     

Gewellt und eben – La6(C2)‐Oktaederschichten in Lanthancarbidchloriden

Sheets of La₆(C₂) Octahedra in Lanthanum Carbide Chlorides – undulated and plane The reaction of Ln, LnCl₃ (Ln = La, Ce) and C yields the hitherto unknown compounds La₈(C₂)₄Cl₅, Ce₈(C₂)₄Cl₅, La₁₄(C₂)₇Cl₉, La₂₀(C₂)₁₀Cl₁₃, La₂₂(C₂)₁₁Cl₁₄, La₃₆(C₂)₁₈Cl₂₃ and La₂(C₂)Cl. The gold‐ resp. bronze‐coloured metallic compounds are sensitive to moisture. The reaction temperatures are 1030 °C, 1000 °C, 970 °C, 1020 °C, 1020 °C, 1080 °C and 1030 °C in the order of compounds given, which mostly crystallize in the monoclinic space group P2₁/c with a = 7.756(1) Å, b = 16.951(1) Å, c = 6.878(1) Å, β = 104.20(1)° (La₈(C₂)₄Cl₅), a = 7.669(2) Å, b = 16.784(3) Å, c = 6.798(1) Å, β = 104.05(1)° (Ce₈(C₂)₄Cl₅), a = 7.669(2) Å, b = 16.784(3) Å, c = 6.789(1) Å, β = 104.05(3)° (La₂₀(C₂)₁₀Cl₁₃), a = 7.770(2) Å, b = 47.038(9) Å, c = 6.901(1) Å, β = 104.28(3)° (La₂₂(C₂)₁₁Cl₁₄) and a = 7.764(2) Å, b = 77.055(15) Å, c = 6.897(1) Å, β = 104.26(3)° (La₃₆(C₂)₁₈Cl₂₃), respectively. La₁₄(C₂)₇Cl₉‐(II) crystallizes in Pc with a = 7.775(2) Å, b = 29.963(6) Å, c = 6.895(1) Å, β = 104.21(3)° and La₂(C₂)Cl in C2/c with a = 14.770(2) Å, b = 4.187(1) Å, c = 6.802(1) Å, β = 101.50(3)°. The crystal structures are composed of distorted C₂ centered La‐octahedra which are condensed into chains via common edges. Three and four such chains join into ribbons, and these are connected into undulated layers with Cl atoms between them. The variations of the structure principle are analyzed systematically.     

Crystal structure of a new molecular complex of fullerene with tetramethyltetraselenafulvalene: C60·TMTSF·2CS2

A new molecular complex of fullerene with tetramethyltetraselenafulvalene (TMTSF), C₆₀·TMTSF·2CS₂, (1) was synthesized. The structure and composition of the complex were established by X-ray diffraction analysis. The crystals of C₆₀·C₁₀H₁₂Se₄·2CS₂ are monoclinic:a=15.407(2),b=12.934(2),c=12.026(2) Å β=108.39(3)°,V=2274.1(6) ų, space groupCm, Z=2,d _calc=1.929 g cm^?3,R=0.047. The crystal structure of 1 consists of layers. Layers formed by fullerene and CS₂ molecules alternate with layers of TMTSF molecules. Peculiarities of the crystal structure of 1 are the nonplanar conformation of TMTSF molecules and the absence of shortened C…C contacts between adjacent fullerenes molecules. The energy of intermolecular TMTSF…C₆₀ interactions in the crystal was estimated.     

Aluminiumorganyle mit pentakoordiniertem Aluminium-Atom: Synthese und Molekülstrukturen von [AlX2{2,6-(NEt2CH2)2C6H3}] (X = Cl,Et, H)

Aluminium Organyls with Pentacoordinate Aluminium: Syntheses and Molecular Structures of [AlX₂{2,6-(NEt₂CH₂)₂C₆H₃}] (X = Cl, Et, H) The reaction of [Li{2,6-(NEt₂CH₂)₂C₆H₃}]₂ with AlCl₃ or Et₂AlCl gives [AlX₂{2,6-(NEt₂CH₂)₂C₆H₃}] [X = Cl ( 1 ), Et ( 2 )] in good yield. 1 reacts with NaH in toluene to give [AlH₂{2,6-(NEt₂CH₂)₂C₆H₃}] ( 3 ). 1–3 were characterised spectroscopically (¹H, ¹³C, ²⁷Al n.m.r., i.r., mass spectroscopy). In solution at room temperature 1–3 exhibit dynamic behaviour. For 1 and 3 this can be frozen out below 278 K (¹H n.m.r.), indicating the presence of monomeric molecules with pentacoordinate Al at low temperature. Such species are also observed in the solid state as shown by an X-ray structure determination on 1 (monoclinic space group P2₁/n, a = 9.7325(14), b = 13.552(5), c = 28.858(7) Å, β = 99.57(2)°, V = 3753(2) ų, Z = 8, at 223(2) K) and 2 (monoclinic space group C2/c, a = 15.0045(12), b = 9.2986(8), c = 14.9955(12) Å, β =99.512(1)°, Z = 4, at 223(2) K).     

Rb{Pr6C2}I12, an Iodide with a 13‐Electron Isolated Octahedral {Pr6C2} Cluster

Rb{Pr₆(C)₂}I₁₂ was obtained from a mixture of RbI, PrI₃, Pr and C as black single crystals at elevated temperatures. The black crystals are triclinic, (no. 2), a = 960.1(2), b = 957.0(2), c = 1003.4(2) pm, α = 71.74(2), β = 70.69(2), γ = 72.38(2)°, V = 805.6(3) 10⁶ pm³, Z = 1; R₁ = 0.0868 for all 2749 measured independent reflections. Rb{Pr₆(C)₂}I₁₂ contains {Pr₆(C₂)} clusters isolated from each other, surrounded by twelve edge‐bridging and six terminal ligands. The [{Pr₆(C)₂}Iⁱ₁₂I^a₆]^? units are connected via i‐a/a‐i bridges according to {Pr₆C₂}Iⁱ_6/1I^i‐a_6/2I^a‐i_6/2 with rubidium ions occupying twelve‐coordinate interstices.