Thermodynamics of Bromo-Adamantane and Carbon Tetrabromide Under Pressure

Excess molar volumes at 298.15 K of the ternary system {CH₃(CH₂)₂CO₂(CH₂)₃CH₃+ CH₃(CH₂)₇OH+CH₃(CH₂)₆CH₃} and the binary mixtures {CH₃(CH₂)₂CO₂(CH₂)₃CH₃+ CH₃(CH₂)₇OH}, {CH₃(CH₂)₂CO₂(CH₂)₃CH₃+CH₃ (CH₂)₆CH₃} and {CH₃(CH₂)₇OH+ CH₃(CH₂)₆CH₃} were determined using an Anton Paar DMA 60/602 densimeter. All experimental values were compared with the results obtained with empirical expressions for estimation of the ternary properties from the binary data. Variable-degree polynomials were fitted to the results. This revised version was published online in July 2006 with corrections to the Cover Date.     

Zur Kenntnis der Dialkalimetalldichalkogenide β-Na2S2, K2S2, α-Rb2S2, β-Rb2S2, K2Se2, Rb2Se2, α-K2Te2, β-K2Te2 und Rb2Te2

On Dialkali Metal Dichalcogenides β-Na₂S₂, K₂S₂, α-Rb₂S₂, β-Rb₂S₂, K₂Se₂, Rb₂Se₂, α-K₂Te₂, β-K₂Te₂ and Rb₂Te₂ The first presentation of pure samples of α- and β-Rb₂S₂, α- and β-K₂Te₂, and Rb₂Te₂ is described. Using single crystals of K₂S₂ and K₂Se₂, received by ammonothermal synthesis, the structure of the Na₂O₂ type and by using single crystals of β-Na₂S₂ and β-K₂Te₂ the Li₂O₂ type structure will be refined. By combined investigations with temperature-dependent Guinier-, neutron diffraction-, thermal analysis, and Raman-spectroscopy the nature of the monotropic phase transition from the Na₂O₂ type to the Li₂O₂ type will be explained by means of the examples α-/β-Na₂S₂ and α-/β-K₂Te₂. A further case of dimorphic condition as well as the monotropic phase transition of α- and β-Rb₂S₂ is presented. The existing areas of the structure fields of the dialkali metal dichalcogenides are limited by the model of the polar covalence.     

Equilibrium phase behavior of aqueous two-phase systems containing 17R4/L64 and citrates

The cloud points (CPs) of the copolymers 17R4 and L64 were first measured, and then the effects of salts ((NH₄)₃C₆H₅O₇, K₃C₆H₅O₇) on 17R4 and L64 were researched. After finishing the work described above, the temperature (278.15, 283.15, and 288.15) K of aqueous two-phase systems was determined, which consist of 17R4-(NH₄)₃C₆H₅O₇, 17R4-K₃C₆H₅O₇, L64-(NH₄)₃C₆H₅O₇, and L64-K₃C₆H₅O₇. Finally, the liquid–liquid equilibrium (LLE) data of binodal curve and the tie line for 17R4-(NH₄)₃C₆H₅O₇ aqueous two- phase systems (ATPSs) 17R4-K₃C₆H₅O₇ ATPSs, L64-(NH₄)₃C₆H₅O₇ ATPSs, and L64-K₃C₆H₅O₇ ATPSs were obtained. Nonlinear fitting of the empirical equation was used for making the diagram. The results showed that the change in the size of the two-phase areas increases with the increase of temperature. The capacity of the salts to induce phase segregation follows the Hofmeister series, that is, K₃C₆H₅O₇?>?(NH₄)₃C₆H₅O₇. In addition, the findings also showed that the phase separation ability of 17R4 is better than that of L64.     

Piperazine Functionalization of C70 for Incorporation into Supramolecular Assemblies

The photochemical reaction of piperazine with C₇₀ produces a mono‐adduct (N(CH₂CH₂)₂NC₇₀) in high yield (67 %) along with three bis‐adducts. These piperazine adducts can combine with various Lewis acids to form crystalline supramolecular aggregates suitable for X‐ray diffraction. The structure of the mono‐adduct was determined from examination of the adduct I₂N(CH₂CH₂)₂NI₂C₇₀ that was formed by reaction of N(CH₂CH₂)₂NC₇₀ with I₂. Crystals of polymeric {Rh₂(O₂CCF₃)₄N(CH₂CH₂)₂NC₇₀}_n?nC₆H₆ that formed from reaction of the mono‐adduct with Rh₂(O₂CCF₃)₄ contain a sinusoidal strand of alternating molecules of N(CH₂CH₂)₂NC₇₀ and Rh₂(O₂CCF₃)₄ connected through Rh?N bonds. Silver nitrate reacts with N(CH₂CH₂)₂NC₇₀ to form black crystals of {(Ag(NO₃))₄(N(CH₂CH₂)₂NC₇₀)₄}_n?7nCH₂Cl₂ that contain parallel, nearly linear chains of alternating (N(CH₂CH₂)₂NC₇₀ molecules and silver ions. Four of these {Ag(NO₃)N(CH₂CH₂)₂NC₇₀}_n chains adopt a structure that resembles a columnar micelle with the ionic silver nitrate portion in the center and the nearly non‐polar C₇₀ cages encircling that core. Of the three bis‐adducts, one was definitively identified through crystallization in the presence of I₂ as ¹²{N(CH₂CH₂)₂N}₂C₇₀ with addends on opposite poles of the C₇₀ cage and a structure with C_2v symmetry. In ¹²{I₂N(CH₂CH₂)₂N}₂C₇₀, individual ¹²{I₂N(CH₂CH₂)₂N}₂C₇₀ units are further connected by secondary I2???N2 interactions to form chains that occur in layers within the crystal. Halogen bond formation between a Lewis base such as a tertiary amine and I₂ is suggested as a method to produce ordered crystals with complex supramolecular structures from substances that are otherwise difficult to crystallize.     

Phosphonitrilic Chloride. 40. Relationships between Electrical Conductivity and Thermal Behavior of Diaminotetraarylcyclotriphosphazenes

The behavior of various diaminotetraarylcyclotriphosphazenes N₃P₃(NH₂)₂R₄ on heating has been studied. The homocondensation reaction occurs with elimination of ammonia or aniline when the N₃P₃(NH₂)₂(OC₆H₅)₄, N₃P₃(NH₂)₂ (C₆H₅)₄, or N₃P₃ (NHC₅H₅)₆ is heated under various conditions. However, the homocondensation reaction does not proceed in case of N₃P₃ (NH₂)₂ (SC₆H₅)₄ because of the high conductivity of this compound.     

From Saturated BN Compounds to Isoelectronic BN/CC Counterparts: An Insight from Computational Perspective

In the present study, the inorganic analogues of alkanes as well as their isoelectronic BN/CC counterparts that bridge the gap between organic and inorganic chemistry are comparatively studied on the grounds of static DFT and Car–Parrinello molecular dynamics simulations. The BN/CC butanes CH₃CH₂BH₂NH₃, BH₃CH₂NH₂CH₃, and NH₃CH₂BH₂CH₃ were considered and compared with their isoelectronic counterparts NH₃BH₂NH₂BH₃ and CH₃CH₂CH₂CH₃. In addition, systematical replacement of the NH₂BH₂ fragment by the isoelectronic CH₂CH₂ moiety is studied in the molecules H₃N(NH₂BH₂)_3–m(CH₂CH₂)_mBH₃ (for m=0, 1, 2, or 3) and H₃N(NH₂BH₂)_2–m(CH₂CH₂)_mBH₃ (for m=0, 1, or 2). The DFT and Car–Parrinello simulations show that the isosteres of the BN/CC butanes CH₃CH₂BH₂NH₃, BH₃CH₂NH₂CH₃, and NH₃CH₂BH₂CH₃ and of larger oligomers of the type (BN)_k(CC)_l where k≥l are stable compounds. The BN/CC butane H₃NCH₂CH₂BH₃ spontaneously produces molecular hydrogen at room temperature. The reaction, prompted by very strong dihydrogen bonding NH???HB, undergoes through the neutral, hypervalent, pentacoordinated boron dihydrogen complex R?BH₂(H₂) [R=(CH₂CH₂)_nNH₂]. The calculations suggest that such intermediate and the other BN/CC butanes CH₃CH₂BH₂NH₃, BH₃CH₂NH₂CH₃, and NH₃CH₂BH₂CH₃ as well as larger BN/CC oligomers are viable experimentally. A simple recipe for the synthesis of CH₃CH₂BH₂NH₃ is proposed. The strength of the dihydrogen bonding appeared to be crucial for the overall stability of the saturated BN/CC derivatives.     

Synthesis of Inorganic Structural Isomers By Diffusion‐Constrained Self‐Assembly of Designed Precursors: A Novel Type of Isomerism

The structure of precursors is used to control the formation of six possible structural isomers that contain four structural units of PbSe and four structural units of NbSe₂: [(PbSe)_1.14]₄[NbSe₂]₄, [(PbSe)_1.14]₃[NbSe₂]₃[(PbSe)_1.14]₁[NbSe₂]₁, [(PbSe)_1.14]₃[NbSe₂]₂[(PbSe)_1.14]₁[NbSe₂]₂, [(PbSe)_1.14]₂[NbSe₂]₃[(PbSe)_1.14]₂[NbSe₂]₁, [(PbSe)_1.14]₂[NbSe₂]₂[(PbSe)_1.14]₁[NbSe₂]₁[(PbSe)_1.14]₁[NbSe₂]₁, [(PbSe)_1.14]₂[NbSe₂]₁[(PbSe)_1.14]₁[NbSe₂]₂[(PbSe)_1.14]₁[NbSe₂]₁. The electrical properties of these compounds vary with the nanoarchitecture. For each pair of constituents, over 20 000 new compounds, each with a specific nanoarchitecture, are possible with the number of structural units equal to 10 or less. This provides opportunities to systematically correlate structure with properties and hence optimize performance.     

Synthesis and characterization of organotin complexes with dithiocarbamates and crystal structures of (4‐NCC6H4CH2)2Sn(S2CNEt2)2 and (2‐ClC6H4CH2)2 Sn(Cl)S2CNBz2

Ten organotin derivatives with dithiocarbamates of the formulae (4‐NCC₆H₄CH₂)₂Sn(S₂CNEt₂)₂ (1), (4‐NCC₆H₄CH₂)₂Sn(S₂CNBz₂)₂ (2), (4‐NCC₆H₄CH₂)₂Sn[S₂CN(CH₂CH₂)₂NCH₃]₂ (3), (2‐ClC₆H₄CH₂)₂ Sn(S₂CNEt₂)₂ (4), (2‐ClC₆H₄CH₂)₂Sn(S₂CNBz₂)₂ (5), (4‐NCC₆H₄CH₂)₂Sn(Cl)S₂CNEt₂ (6), (4‐NCC₆H₄CH₂)₂Sn(Cl)S₂CNBz₂ (7), (4‐NCC₆H₄CH₂)₂Sn(Cl)S₂CN(CH₂CH₂)₂NCH₃ (8), (2‐ClC₆H₄CH₂)₂ Sn(Cl)S₂CNEt₂ (9) and (2‐ClC₆H₄CH₂)₂Sn(Cl)S₂CNBz₂ (10) have been prepared. All complexes were characterized by elemental analyses, IR and NMR. The crystal structures of complexes 1 and 10 were determined by X‐ray single crystal diffraction. For complex 1, the central tin atom exists in a skew‐trapezoidal planar geometry defined by two asymmetrically coordinated dithiocarbamate ligands and two 4‐cyanobenzyl groups. In addition, because of the presence of close intermolecular non‐bonded contacts, complex 1 is a weakly‐bridged dimer. In complex 10, the central tin atom is rendered pentacoordinated in a distorted trigonal bipyramidal configuration by coordinating with S atoms derived from the dithiocarbamate ligand. In vitro assays for cytotoxicity against five human tumor cell lines (MCF‐7, EVSA‐T, WiDr, IGROV and M226) furnished the significant toxicities of the title complexes. Copyright © 2006 John Wiley & Sons, Ltd.     

Reactivity in the solid state between CoWO4 and RE2WO6 where RE = Sm, Eu, Gd

Reactivity in the solid state between CoWO₄ and some rare-earth metal tungstates RE₂WO₆ (RE = Sm, Eu, Gd) was investigated by the XRD method. Two families of new isostructural cobalt and rare-earth metal tungstates, Co₂RE₂W₃O₁₄ and CoRE₄W₃O₁₆, were synthesized. The Co₂RE₂W₃O₁₄ phases are formed by heating in air the CoWO₄ and RE₂WO₆ compounds mixed at the molar ratio 2:1, while the CoRE₄W₃O₁₆ phases are synthesized at the molar ratio of CoWO₄/RE₂WO₆ equals to 1:2. The Co₂RE₂W₃O₁₄ phases as well as the CoRE₄W₃O₁₆ compounds crystallize in the orthorhombic system. The Co₂RE₂W₃O₁₄ and CoRE₄W₃O₁₆ compound melt above 1150 °C. A melting manner of the Co₂RE₂W₃O₁₄ and CoRE₄W₃O₁₆ compounds was determined in an inert atmosphere. The formation of CoWO_4−x phase was observed during heating in an inert atmosphere.     

Oxalate-2-ethanolamine complexes of some bivalent cations (Mn,Co, Ni,Cu, Zn and Cd)

On the refluxing ofM(II) oxalate (M=Mn, Co, Ni, Cu, Zn or Cd) and 2-ethanolamine in chloroform, the following complexes were obtained: MnC₂O₄·HOCH₂CH₂NH₂·H₂O, CoC₂O₄·2HOCH₂CH₂NH₂, Ni₂(C₂O₄)₂·5HOCH₂CH₂NH₂·3H₂O, Cu₂(C₂O₄)₂·5HOCH₂CH₂NH₂, Zn₂(C₂O₄)₂·5HOCH₂CH₂NH₂·2H₂O and Cd₂(C₂O₄)₂·HOCH₂CH₂NH₂·2H₂O. Following the reaction ofM(II) oxalate with 2-ethanolamine in the presence of ethanolammonium oxalate, a compound with the empirical formula ZnC₂O₄·HOCH₂CH₂NH₂·2H₂O¹ was isolated. The complexes were identified by using elemental analysis, X-ray powder diffraction patterns, IR spectra, and thermogravimetric and differential thermal analysis. The IR spectra and X-ray powder diffraction patterns showed that the complexes obtained were not isostructural. Their thermal decompositions, in the temperature interval between 20 and about 900°C, also take place in different ways, mainly through the formation of different amine complexes. The DTA curves exhibit a number of thermal effects.     

The systems Zr(Nb,Ti)(R)O2−δ, R=Yb, Ca—optimization of mixed conductivity and comparison with results of other systems (R=Y and Gd)

In this work we address the optimization of mixed conductivity in fluorite compounds based on zirconia. Phase relations of the new systems YbO_1.5-NbO_2.5-ZrO₂, and CaO-NbO_2.5-ZrO₂ are presented. The limit of the cubic defect fluorite phase in YbO_1.5-NbO_2.5-ZrO₂ closely resembles that of the system YO_1.5-NbO_2.5-ZrO₂, whilst in CaO-NbO_2.5-ZrO₂ is narrow extending to include composition Ca_0.255Nb_0.15Zr_0.595O_1.82 at 1500°C. The influence of dopant ion size, charge and composition on ionic conduction is assessed and parallels are drawn with the systems YO_1.5-NbO_2.5-ZrO₂ and YO_1.5-TiO₂-ZrO₂. Comparison of these results with published data on the Ti containing systems CaO-TiO₂-ZrO₂, GdO_1.5-TiO₂-ZrO₂ shows that the highest mixed conducting compositions can only be offered in the system YO_1.5-TiO₂-ZrO₂ out of all the systems here studied.     

Abläufe der Ammonolysen der Ammoniumhexafluorometallate des Aluminiums,Galliums und Indiums, (NH4)3MF6 (M = Al,Ga, In)

The Courses of the Ammonolyses of the Ammonium Hexafluorometalates of Aluminum, Gallium, and Indium, (NH₄)₃MF₆ (M = Al, Ga, In) The courses of the ammonolysis reactions of the ammonium hexafluorometalates (NH₄)₃MF₆ (M = Al, Ga, In) were investigated with the aid of in‐situ powder diffractometry and differential thermal analysis. Under these conditions, the reaction of (NH₄)₃AlF₆ with gaseous ammonia yields at about 360 °C AlF₃ via the intermediates NH₄AlF₄, Al(NH₃)₂F₃ and Al(NH₃)F₃. The ammonolysis of (NH₄)₃GaF₆ produces GaN at about 400 °C. Depending upon the actual reaction conditions, the intermediates NH₄GaF₄ and Ga(NH₃)F₃ as well as their ammonia adducts NH₄GaF₄ · NH₃ and Ga(NH₃)₂F₃ and the amide‐ammoniate Ga(NH₃)(NH₂)F₂ are observed. In the case of (NH₄)₃InF₆ the intermediates (NH₄)₃InF₆ · NH₃ and In(NH₃)F₃ may exist; there are also indications for the reduction of In(III) to In(I) and for the existence of In(NH₃)₂F and InF as products of the ammonolysis of (NH₄)₃InF₆.     

Co1−xFe2+xO4 (x = 0.1, 0.2) anode materials for rechargeable lithium-ion batteries

A cobalt-poor or iron rich bicomponent mixture of Co_0.9Fe_2.1O₄/Fe₂O₃ and Co_0.8Fe_2.2O₄/Fe₂O₃ anode materials have been successfully prepared using simple, cost-effective, and scalable urea-assisted auto-combustion synthesis. The threshold limit of lower cobalt stoichiometry in CoFe₂O₄ that leads to impressive electrochemical performance was identified. The electrochemical performance shows that the Co_0.9Fe_2.1O₄/Fe₂O₃ electrode exhibits high capacity and rate capability in comparison to a Co_0.8Fe_2.2O₄/Fe₂O₃ electrode, and the obtained data is comparable with that reported for cobalt-rich CoFe₂O₄. The better rate performance of the Co_0.9Fe_2.1O₄/Fe₂O₃ electrode is ascribed to its unique stoichiometry, which intimately prefers the combination of Fe₂O₃ with Co_1−xFe_2+xO₄ and the high electrical conductivity. Further, the high reversible capacity in Co_0.9Fe_2.1O₄/Fe₂O₃ and Co_0.8Fe_2.2O₄/Fe₂O₃ electrodes is most likely attributed to the synergistic electrochemical activity of both the nanostructured materials (Co_1−xFe_2+xO₄ and Fe₂O₃), reaching beyond the well-established mechanisms of charge storage in these two phases.     

Molecular Cage Assembly by Sn−O−Sn Bridging of Di-, Tri- and Tetranuclear Organotin Tectons: Extending the Spacing in Double Ladder Structures

Hydrolysis reactions of di- and trinuclear organotin halides yielded large novel cage compounds containing Sn−O−Sn bridges. The molecular structures of two octanuclear tetraorganodistannoxanes showing double-ladder motifs, viz., [{Me₃SiCH₂(Cl)SnCH₂YCH₂Sn(OH)CH₂SiMe₃}₂(μ-O)₂]₂ [ 1 , Y=p-(Me)₂SiC₆H₄-C₆H₄Si(Me)₂] and [{Me₃SiCH₂(I)SnCH₂YCH₂Sn(OH)CH₂SiMe₃}₂(μ-O)₂]₂ ⋅ 0.48 I₂ [ 2⋅ 0.48 I₂, Y=p-(Me)₂SiC₆H₄-C₆H₄Si(Me)₂], and the hexanuclear cage-compound 1,3,6-C₆H₃(p-C₆H₄Si(Me)₂CH₂Sn(R)₂OSn(R)₂CH₂Si(Me)₂C₆H₄-p)₃C₆H₃-1,3,6 ( 3 , R=CH₂SiMe₃) are reported. Of these, the co-crystal 2⋅ 0.48 I₂ exhibits the largest spacing of 16.7 Å reported to date for distannoxane-based double ladders. DFT calculations for the hexanuclear cage and a related octanuclear congener accompany the experimental work.     

Präparation und röntgenographische Charakterisierung der Verbindungen Ca3M2Ga2 (M = Pd,Pt) und Ca3M2Ga3 (M = Rh,Ir)

Preparation and Crystal Structures of the Compounds Ca₃Pd₂Ga₂, Ca₃Pt₂Ga₂, Ca₃Rh₂Ga₃, and Ca₃Ir₂Ga₃ The new compounds Ca₃Pd₂Ga₂, Ca₃Pt₂Ga₂, Ca₃Rh₂Ga₃, and Ca₃Ir₂Ga₃ were prepared by heating appropriate mixtures of the elements under an Argon-atmosphere. The results of the structure analysis of single crystals by means of X-ray diffraction are given in the section “Inhaltsübersicht”. Ca₃Pd₂Ga₂ and Ca₃Pt₂Ga₂ are isotypic and form the Y₃Rh₂Si₂ type structure (Pbcm), where the platinium metals have a trigonal environment consisting of Ga-atoms. The isotypic compounds Ca₃Rh₂Ga₃ and Ca₃Ir₂Ga₃ (Pbcm) form a new type of structure, which is related to the Y₃Rh₂Si₂ type with a distorted tetrahedral surrounding of Ga-atoms for Rh (resp. Ir).     

Mono‐ and Perfluoroaryliodine(III) Cyano Compounds – Synthesis,Reactivity, and Structure

C₆F₅I(CN)₂ and x‐FC₆H₄I(CN)₂ (x = 2, 3, 4) were isolated from reactions of the corresponding aryliodine difluorides ArIF₂ and a stoichiometric excess of Me₃SiCN in CCl₃F (0 °C) or CH₂Cl₂ (20 °C), respectively. In addition, x‐FC₆H₄I(CN)₂ compounds were synthesized in good yields on alternative routes, namely from 3‐ or 4‐FC₆H₄I(OC(O)CH₃)₂ or 4‐FC₆H₄I(OC(O)CF₃)₂ or from 4‐FC₆H₄IO and Me₃SiCN in CH₂Cl₂ at 20 °C. In the 1 : 1 reaction of C₆F₅IF₂ and Me₃SiCN a lower temperature was necessary to suppress partial disubstitution and to obtain the first example of a new type of aryliodine(III) cyanide compounds, C₆F₅I(CN)F. 4‐FC₆H₄I(CN)F could be isolated from the equimolar reaction of 4‐FC₆H₄IF₂ and Me₃SiCN in CH₂Cl₂ even at 20 °C. The new products were characterized by multi‐NMR and Raman spectroscopy. The molecular structures of C₆F₅I(CN)₂, 3‐ and 4‐FC₆H₄I(CN)₂, C₆F₅I(CN)F, and 4‐FC₆H₄I(CN)F are discussed and compared with that of C₆F₅IF₂. The reactivity of C₆F₅I(CN)F towards fluoride acceptors EF_n (BF₃, AsF₅) and R_xEX_?x (C₆F₅SiF₃, C₆H₅SiF₃, C₆H₅PF₄, Me₃SiCl, Me₃SiC₆F₅) were investigated and showed differing reaction patterns (fluoride abstraction, aryl transfer, chloride transfer). Besides the molecular entities C₆F₅I(CN)F and C₆F₅I(CN)Cl, the corresponding iodonium salts [C₆F₅(CN)I][BF₄] and [C₆F₅(CN)I][AsF₆] were isolated. The thermal stability of ArI(CN)₂ and ArI(CN)F, neat and in solution, as well as the reactivity of 4‐FC₆H₄I(CN)₂ towards the Lewis acid BF₃ are reported.     

Synthesis and Reactivity of New Functionalized Perfluoroalkylfluorophosphates

A new efficient synthesis of functionalized perfluoroalkyl fluorophosphates by oxidative addition of Me₂NCH₂F to the electron‐deficient phosphanes (C₂F₅)_nPF_3?n (n=0–3) is reported. The initially formed zwitterionic, hexacoordinated phosphates [(C₂F₅)_nF_5?nP(CH₂NMe₂?CH₂NMe₂)] are converted into the corresponding phosphonium salts [(Me₃PCH₂NMe₂]⁺[(C₂F₅)_nF_5?nP(CH₂NMe₂)]^? by treatment with PMe₃. In addition [(C₂F₅)₃F₂P(CH₂NMe₂?CH₂NMe₂)] can undergo a 1,3‐methyl shift from the internal to the terminal nitrogen—a structural characterization was achieved from the CF₃ analogue. Reaction of [(C₂F₅)₃F₂P(CH₂NMe?CH₂NMe₃)] and PMe₃ gave rise to the formation of the zwitterionic phosphonium phosphate [(C₂F₅)₃F₂P(CH₂NMe?CH₂PMe₃)], which was fully characterized by X‐ray diffraction analysis. Moreover, an efficient one‐pot synthesis of Cs⁺[(C₂F₅)₃F₂P(CH₂NMe₂)]^? was pursued. This salt turned out to be a useful nucleophile in several alkylation reactions.     

An unusual organoyttrium alkyl complex containing a [C5HMe3(η(3)-CH2)-C5H4N-κ]- ligand and an elusive cyclopentadienide-based scandium tuck-over zwitterion obtained by C-H bond activation

The acid–base reaction between Y(CH₂SiMe₃)₃(thf)₂ and the pyridyl‐functionalized cyclopentadienyl (Cp) ligand C₅Me₄H? C₅H₄N (1 equiv) at 0 °C afforded a mixture of two products: (η⁵:κ‐C₅Me₄? C₅H₄N)Y(CH₂SiMe₃)₂(thf) ( 1 a ) and (η⁵:κ‐C₅Me₄? C₅H₄N)₂YCH₂SiMe₃ ( 1 b ), in a 5:2 ratio. Addition of the same ligand (2 equiv) to Y(CH₂SiMe₃)₃(thf)₂, however, generated 1 b together with the novel complex 1 c , the first well defined yttrium mono(alkyl) complex (η⁵:κ‐C₅Me₄? C₅H₄N)[C₅HMe₃(η³‐CH₂)‐C₅H₄N‐κ]Y(CH₂SiMe₃) containing a rare κ/η³‐allylic coordination mode in which the C? H bond activation occurs unexpectedly with the allylic methyl group rather than conventionally on Cp ring. If the central metal was changed to lutetium, the equimolar reaction between Lu(CH₂SiMe₃)₃(thf)₂ and C₅Me₄H? C₅H₄N exclusively afforded the bis(alkyl) product (η⁵:κ‐C₅Me₄? C₅H₄N)Lu(CH₂SiMe₃)₂(thf) ( 2 a ). Similarly, the reaction between the ligand (2 equiv) and Lu(CH₂SiMe₃)₃(thf)₂ gave the mono(alkyl) complex (η⁵:κ‐C₅Me₄? C₅H₄N)₂LuCH₂SiMe₃ ( 2 b ), in which no ligand redistribution was observed. Strikingly, treatment of Sc(CH₂SiMe₃)₃(thf)₂ with C₅Me₄H? C₅H₄N in either 1:1 or 1:2 ratio at 0 °C generated the first cyclopentadienide‐based scandium zwitterionic “tuck‐over” complex 3 , (η⁵:κ‐C₅Me₄? C₅H₄N)Sc(thf)[μ‐η⁵:η¹:κ‐C₅Me₃(CH₂)‐C₅H₄N]Sc(CH₂SiMe₃)₃. In the zwitterion, the dianionic ligand [C₅Me₃(CH₂)‐C₅H₄N]^2? binds both to Sc1³⁺ and to Sc2³⁺, in η⁵ and η¹/κ modes. In addition, the reaction chemistry, the molecular structures, and the mechanism are also discussed in detail.     

Reactivity in The Solid State Between Ag2S and Ag2CrO4

Reactivity, in the solid state between Ag₂S and Ag₂CrO₄, was investigated by DTA, XRD and IR methods. It was found that, according to a composition of an initial Ag₂S/Ag₂CrO₄ mixture, the products of a reaction of Ag₂S with Ag₂ CrO₄ can be: solid solution with Ag₂CrO₄ structure (Ag₂Cr_1–xS_xO₄) and AgCrO₂; or solid solution Ag₂Cr_1–xS_xO₄, Ag₂SO₄, AgCrO₂ and metallic silver; or Ag₂S, β-Ag₈S₄O₄, Ag, AgCrO₂, Ag₂SO₄ and Ag₂Cr_1–xS_xO₄ solid solution. This revised version was published online in July 2006 with corrections to the Cover Date.     

Syndiotactic polymerization of styrene catalyzed by alkenyl‐substituted cyclopentadienyltitanium trichlorides

CH₂?CHCH₂CpTiCl₃ (1), CH₂?CHCH₂CH₂CpTiCl₃ (2) and CH₃CH₂CH₃CpTiCl₃ (3) have been synthesized and characterized. The influence of the alkenyl substituent groups on the catalyst activities in the syndiotactic polymerization of styrene was investigated. The catalyst activities decreased in the order CH₂?CHCH₂CH₂CpTiCl₃ > CH₃CH₂CH₂CH₂CpTiCl₃ > CH₃CH₂CH₂CpTiCl₃ > CH₂?CHCH₂CpTiCl₃ (Cp?C₅H₄). By using complex 1, the dependence of the activity on the concentration of methylaluminoxane, triisobutylaluminum and diisobutylaluminum hydride was investigated. Copyright © 2003 John Wiley & Sons, Ltd.