Structural studies in main group chemistry : XIX. Organotin(IV) derivatives of tetracyanoethylene, 7,7,8,8-tetracyanoquinodimethane and 2,3,5,6-tetrachlorobenzoquinone. The isolation of stable organotin-substituted radicals

The reaction of organotin chlorides with the lithium salt of 7,7,8,8-tetracyanoquinodimethane (TCNQ) or hexaalkylditins with TCNQ yield stable organotin-substituted free radicals of the types R₃SnTCNQ^. (R = Me, n-Pr, n-Bu) and Me₂Sn(TCNQ^.)₂. The reaction of hexaphenylditin with TCNQ yields a (σ → π) charge transfer complex of stoichiometry (Ph₃SnSnPh₃)·TCNQ, whilst [Me₂SnCl(terpyridyl)⁺](TCNQ^-·) was isolated from the reaction of [Me₂SnCl(terpyridlyl)⁺][Me₂SnCl₃^-] and LiTCNQ. The oxidation of hexaalkylditins by tetracyanoethylene (TCNE) yields stable free radicals of the type R₃SnTCNE·, but treatment with 2,3,5,6-tetrachlorobenzoquinone yields either R₃SnOC₆Cl₄O·-p (R = Me) or R₃SnOC₆Cl₄OSnR₃-p (R = n-Bu, Ph). Tin-119 Mössbauer spectroscopy shows that the derivatives R₃SnTCNQ· and R₃TCNE· have trigonally-bipyramidally coordinated tin with planar [SnC₃] skeletons and bridging [TCNQ·] and [TCNE·] groups forming infinite one-dimensional chain structures. Me₃SnOC₆Cl₄O·-p was inferred to possess a similar structure but with oxy bridges forming chains with a Sn---O---Sn---O backbone. Me₂Sn(TCNQ·)₂ has a structure intermediate between tetrahedral and octahedral with a non-linear MeSnMe unit and anisobidentate chelation by two TCNQ groups. The TCNQ derivatives were of two types: (i) “green” or “brown”, indicative of delocalisation of the Ione electron over the cyanoquinone ligand, and (ii) a “blue” form in which spin-pairing of the Ione electron between adjacent organic groups takes place. Me₃SnTCNQ· may exist in both forms depending upon the mode of preparation.     

Das Schwingungsspektrum von Magnesium-orthovanadat

The infrared and laser-Raman spectra of crystalline Mg₃(VO₄)₂ are reported and a factor group analysis for the full lattice is presented to support the discussion. The 1,000 to 600 cm^?1 region of the spectrum is essentially related to internal (stretching) modes of the greatly distorted VO₄ tetrahedra, whereas the bands in the low frequency region must be assigned to complex vibrations originating in the interaction of the bending vibrations of the tetrahedral groups with the external modes.     

Coordination properties of a diarylaza crown ether appended with a luminescent [Ru(bipy)3]2+ unit

The [Ru(bipy)(2)(1)](PF(6))(2) (bipy refers to 2,2'-bipyridine) complex, comprising a ruthenium(II) tris(2,2'-bipyridine) luminophore covalently linked to a di[(o-triethyleneglycoxy)phenyl]amine crown ether 1, has been synthesized and fully characterized. The photophysical properties of this metal complex have been examined in solution at ambient temperature. Luminescence from the metal complex is enhanced significantly in the presence of various adventitious cations, including protons. In particular, Li(+) cations bind to the crown ether, as evidenced by (1)H NMR and luminescence spectroscopy. Cation binding serves to decrease the rate of reductive quenching of the triplet state of the metal complex, thereby increasing the extent of luminescence. The solution-phase conformation of [Ru(bipy)(2)(1)](PF(6))(2), with and without encapsulated Li(+), has been examined by 2-D NMR and by molecular dynamics simulations.     

1,1,3,3-Tetramethylguanidine-gallane, (Me2N)2CN(H).GaH3: an unusually strongly bound gallane adduct

The novel adduct 1,1,3,3-tetramethylguanidine-gallane, (Me2N)2CN(H).GaH3, has been prepared by the reaction of [(Me2N)2CNH2]+Cl- with LiGaH4 in Et2O solution. Its spectroscopic properties indicate a monomeric species with an unusually strong coordinate link between the imido function and GaH3, an inference confirmed by the crystal structure at 150 K which also reveals significant secondary interactions through non-classical N-H...H-Ga bridges. Despite the intrinsic strength of the Ga-N bond, however, vaporisation at ca. 310 K occurs with partial dissociation, and decomposition via more than one pathway proceeds at temperatures >330-350 K to give a variety of products, including the free base, Me2NH, H2, and a novel gallium-nitrogen compound composed of a Ga4N4 cubane-like core bridged on three edges by -N{C(NMe2)2}GaH2- units.     

Das dielektrische Verhalten von Polyäthern zwischen Mikrowellen- und Infrarot-Gebiet

Zusammenfassung Es wurde die Absorption und Dispersion verschiedener Polyäther im Mikrowellengebiet und im fernen IR untersucht. Mit wachsender Sauerstoffzahl in der Kette werden die Torsions- und Biegeschwingungen wachsend IR-aktiv. Ihre Frequenzlagen ändern sich mit dem zunehmend polaren Charakter der Struktur. Die Analogie zwischen der Verschiebung der Schwingungsfrequenzen und dem Verlauf der Schmelztemperaturen wird diskutiert.Mit zunehmend polarem Charakter steigen der Temperaturkoeffizient der Molpolarisation und die Differenz (–n ²) der Dielektrizitätskonstanten im Mikrowellengebiet und im optischen Bereich stark an. Ein Vergleich mit der Höhe der Dispersionsstufen im fernen IR und deren Temperaturabhängigkeit ergab, daß diese zusätzliche Polarisation nicht allein durch die IR-aktiven Banden bedingt ist. Sie muß gekoppelt sein mit dem ebenfalls stark anwachsenden Untergrundverlust im gesamten mm- und sub-mm-Gebiet.

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Summary Absorption and dispersion of several polyethers were measured in the microwave region and in the far infrared. The torsional vibrations become increasingly iractive with increasing number of oxygens in the chain. Their frequencies shift, too, in a manner analogues to the variation of the melting temperatures.The temperature coefficient of the mol polarization at 32 GHz and the difference (–n ²) between microwave and optical dielectric constant rise rapidly with increasing polar character of the structure. It was tried to correlate (–n ²) with the overall absorption of the skeletal vibrations. Height and temperature dependence of the far ir dispersion show, however, that the larger part of this additional polarization cannot be accounted for by the resonance absorption bands. It must be correlated with the background loss which extends over the whole mm and sub-mm range and also increases rapidly with increasingly polar structure.

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Mit 10 Abbildungen in 14 Einzeldarstellungen und 2 Tabellen     

Swelling effect onα-relaxation in high density polyethylene

Summary Swelling effects of carbon tetrachloride on the mechanical relaxations in the crystal mat and the melt-crystallized samples of high density polyethylene were studied using a torsion pendulum. A very strong-relaxation peak appears by swelling at the low temperature side of the original-relaxation for the crystal mat. It was shown that this strong-relaxation originates from the slippage between the highly swollen lamellae. For the melt-crystallized sample, the-relaxation peak is decreased by swelling, but its temperature is unchanged. This behavior suggests that the-relaxation in the melt-crystallized sample originates mainly from deformation process of intermosaic block region. The swelling effect on-relaxation was also discussed.

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Zusammenfassung Quellungseffekte von Tetrachlorkohlenstoff auf das mechanische Relaxationsverhalten in Einkristall-Matten und schmelzkristallisierten Proben von linearem Polyäthylen wurden mit den Torsionspendeln untersucht. Ein sehr starkes-Maximum tritt durch die Quellung bei tieferen Temperaturen als der der-Relaxation in den nicht gequollenen Einkristall-Matten auf. Es wird gezeigt, daß diese starke-Relaxation auf das Gleiten der ausreichend gequollenen Lamellen zurückzuführen ist. Bei schmelzkristallisierten Proben wird das-Maximum durch die Quellung erniedrigt, seine Temperaturlage wird jedoch nicht verändert. Dies zeigt, daß die-Relaxation in der schmelzkristallisierten Probe hauptsäcblich auf Deformations-Prozessen in den Blöcken beruht. Auch die Quellungseffekte auf die-Relaxationen wurden diskutiert.

     

Orbital correlation effects: The independent pair-potential approximation with application to the ground state and first ionized state of boron hydride

A new method is proposed for calculating correlation effects in atomic and molecular systems. The basis of the method is the formulation of a set of partial configuration expansions which yield directly variational orbital correlation corrections which are appropriately summed in order to obtain an estimate of the total correlation energy. This method is applied to the ground state of boron hydride and its cation at the equilibrium distance of BH. The results of the method are compared in detail with independent electron pair results and second order CI results. It is further shown that multiple substitutions are approximately accounted for in this method and the extent to which they are included is compared with other approximations. Finally, three methods of increasing accuracy, aimed at reducing the necessary computational effort, are given for determining the vertical ionization potential. The most economical method yields an IP of 9.70 eV or 0.03 eV less than the experimental IP. Completion of the basis is estimated to improve this value to 9.77 eV.     

A new paradigm for cationic cyclization of iron tricarbonyl diene complexes with pendant alkenes and arenes

A new example of stereospecific cationic cyclization of iron tricarbonyl diene complexes with pendant alkenes and arenes is provided. Protonation of a double bond vicinal to the iron tricarbonyl diene moiety is employed to trigger the cyclization, rather than the previously reported Lewis/protic acid dehydroxylation of diastereomeric alcohols, eliminating one step of separation and avoiding some reactivity problems previously encountered for one of the alcohol diastereoisomers. [reaction: see text]     

Formation and Crystal Structure of [(F5TeOXe)+·SO2ClF][Sb(OTeF5)6-]

Xe(OTeF₅)₂ reacts with Sb(OTeF₅)₃ under the formation of [Xe₂(OTeF₅)₃]⁺[Sb(OTeF₅)₆]^-. From SO₂ClF solution a yellow solvate [F₅TeOXe]⁺·SO₂ClF· [Sb(OTeF₅)₆]^- is formed with the crystal data: a = 1028.1(1), b = 1040.9(1), c = 1780.2(3) pm, α = 98.07(1), β = 97.68(1), γ = 105.82(1)°, space group . The O-Xe···O fragment is essentially linear (176.1(2)°), and the two Xe-O distances are quite different 197.1(4) and 242.6(4) pm.