Synthesen im system {carbonylmetallat/ketenimin/säure}: XXX. Neue ferra- und rhenaazetidine

The metal carbonyl anions [Fe(η-C₅H₅(CO)₂]^? and [Re(CO)₅] undergo regio- and site-specific [2 + 2]-cycloadditions with the ketenimines Ph₂CCNR (R = Me, Ph) to give the (isolable) anionic complexes [L_n$\text{M{C(CPh}{}_2\text{)N(R)C}$(O)}]^? (L_nM = Fe(η-C₅H₅)CO, Re(CO)₄) which have been alkylated and acylated at the exocyclic oxygen atom of the carbonyl function. The result is stable neutral complexes having a metallaazetidine structure which is composed of an α-metallated enamine and an N,O carbene part. IR, ¹H, and ¹³C NMR data are presented.     

Notiz über den α-LiFeO2-Typ: NaPrO2 und NaTbO2

On the α-LiFeO₂ Type of Structure: NaPrO₂ and NaTbO₂ For the first time transparent light-green single crystals of NaPrO₂ [from PrO_1,833: KO_0,50:NaO_0,50 = 1:1.1:1.2 Ni-cylinder, 1000°C, 20 d] and colourless single crystals of hitherto unknown NaTbO₂ [from Na₂TbO₃, Ni-cylinder, 1000°C, 10 d] have been prepared and investigated by X-ray. The tetragonal α-LiFeO₂-type is confirmed. [NaPrO₂: a = 476.19(3), c = 1096.09(11) pm, c/a = 2.30; 107 I₀ (hkl); R = 4.25% R_w = 3.39%, MoKα; NaTbO₂: a = 463.11(3), c = 1037.39(12) pm, c/a = 2.24; 103 I₀ (hkl); R = 3.54%; R_w = 2,81%; MoKα; both space group I4₁/a m d; fourcircle diffractometer Philips PW 1100]. The Madelung Part of Lattice Energy, MAPLE, and the peculiarities of this type of structure are discussed.     

Fundamental metal carbonyl equilibria: a quantitative infrared spectroscopic study of the equilibrium between dicobalt octacarbonyl and tetracobalt dodecacarbonyl under carbon monoxide pressure in hexane solution.

The equilibrium between Co₂(CO)₈ and Co₄(CO)₁₂ has been investigated in hexane solution in the temperature range 105–145°C under carbon monoxide pressure (6–14 bar). the data obtained by infrared analytical monitoring of the system in a high-pressure cell alow a reasonably precise extension of the calculated equilibrium concentration between —20 and 300°C. The thermo- dynamic parameters obtained for this system are: ΔH⁰ 29.5 ± 0.5 kcal mol^-1, ΔS⁰ 135 ± 3 cal mol^-1 K^-1. The stability regions of Co₂(CO)₈ and Co₄(CO)₁₂ in terms of p(CO) and temperature are discussed.     

Negativer linearer thermischer Ausdehnungskoeffizient von verstrecktem Polyäthylen

Zusammenfassung Der lineare thermische Ausdehnungskoeffizient von linearem Polyäthylen hoher Dichte wurde im Temperaturbereich –20 °C bis + 40°C bestimmt. Bei isotropen Proben besteht eine lineare Beziehung zwischen Dichte bzw. Kristallisationsgrad _v und. Die gemessenen Koeffizienten liegen fürT ₀ = 20 °C im Bereich = 110 ... 130 · 10^–6 K^–1.Kalt verstreckte Proben mit Verstreckungsgraden = 8 ... 15 haben beiT ₀ = 20 °C in Verstreckrichtung den Koeffizienten _l = –24 · 10^–6 K^–1. Der negative Zahlenwert von _tl ist unabhängig von und weiteren Herstellungsparametern. Seine Ursache ist einerseits die Orientierung derc-Achsen der Kristallite in Verstreckrichtung mit _c = –12 · 10^–6 K^–1 und andererseits der negative Koeffizient _am * –50 · 10^–6 K^–1 der verspannten amorphen Phase, der auf dem gummielastischen Verhalten der tie-molecules beruht.Beim Tempern oberhalb von +40 °C schrumpfen die Proben irreversibel, wobei _| ansteigt und nach dem Aufschmelzen der Proben wieder den Wert des isotropen Materials annimmt. Nach dem Tempern wenig unterhalb der Schmelztemperatur der Kristallite wurden überhöhte Koeffizienten _| gemessen, die eine Rotation der Kristallite um dieb-Achsen erkennen lassen.

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Summary The linear thermal coefficient of expansion,, of high density linear polyethylene has been determined in the temperature range of –20 ° ... + 40 °C. For isotropic samples a linear relationship between density or crystallinity _v and is valid. Measured values of forT ₀ = 20 °C amount to = 110 ... 130 · 10^–6 K^–1.Cold drawn samples of draw ratios = 8 ... 15 yield _| = –24 · 10^–6 K^–1 atT ₀ = 20 °C parallel to the draw axis. The negative value of _| does not depend on draw ratio or other parameters of sample processing. It is caused byc-axis orientation of the crystallites in draw direction with _c = –12 · 10^–6 K^–1 and by a negative coefficient _am * = –50 · 10^–6 K^–1 of the stressed amorphous phase, which is due to rubber elastic behaviour of the tie molecules.When annealed above 40 °C the samples shrink irreversibly and _| is augmented. After melting the samples the value of isotropic material is restored. Annealing the samples little below the melting temperature of the crystallites leads to superelevated values all which reflect| rotation of the crystallites around theb-axis.

     

Eine Notiz zum A-Typ der Lanthanoidoxide: Über Pr2O3

The A-type of Lanthanoide Oxides: On Pr₂O₃ . “Reductive” thermal decomposition of K₂PrO₃ [Ni-cylinder, semi-open system, 1000°C, 14 d] leads for the first time to light green single crystals of Pr₂O₃. The structure determination [105 symmetry independent hkl, four circle diffractometer Philips PW 1100; MoKα; R = 6.30%, R_w = 5.01%; space group P3m1; Z = 1; a = 385.77(3), c = 601.20(6) pm] verifies the A-type according to the proposed structure by PAULING .     

Reaction of K[(π-C5H5)Fe(CO)(CN)2] with boranes and AlCl3: Preparation and investigation of iron(II) complexes containing isocyanoborate ligands

Iron(II) complexes containing CNBX^?₃ or CNBX₂NC^? ligands were prepared from the reaction of K[(π-C₅H₅)Fe(CO)(CN)₂] with boranes (BX₃; X = F, Cl, Br H, Ph). Stable, twelve-membered ring compounds containing Fe, C, N, and B atoms were formed involving CNBF₂NC^? and CNBBr₂NC^? ligands. The reaction of K[(π-C₅H₅)Fe(CO)(CN)₂] with AlCl₃ gave a four-center complex with two Fe and two Al atoms. The compounds were studied by infrared and mass spectroscopic methods.