Preparation of silyl-terminated branched polyethylenes catalyzed by Brookhart's nickel diimine complex activated with hydrosilane/B(CF).

Brookhart's nickel α-diimine complex [(κ-,-BIAN)NiCl] (1) (where BIAN = {Ar-NAceN-Ar}, Ace = acenaphthen-1,2-diyl, and Ar = 2,6-(iPr)-CH) activated with a hydrosilane/B(CF) (SiHB) adduct forms a highly active catalytic system for ethylene polymerization. Under optimal conditions, the activity of the system depends on the nature of hydrosilane and decreases in the order RSiH > PhSiH > PhSiH. The decrease in system activity within the hydrosilane series is correlated with increasing formation of Ni(I) species.

Lewis Acidic Aluminosilicates: Synthesis, Al MQ/MAS NMR, and DFT-Calculated Al NMR Parameters.

Porous aluminosilicates are functional materials of paramount importance as Lewis acid catalysts in the synthetic industry, yet the participating aluminum species remain poorly studied. Herein, a series of model aluminosilicate networks containing [L-AlO] (L = THF, EtN, pyridine, triethylphosphine oxide (TEPO)) and [AlO] centers were prepared through nonhydrolytic sol-gel condensation reactions of the spherosilicate building block (MeSn)SiO with L-AlX (X = Cl, Me, Et) and [MeN] [AlCl] compounds in THF or toluene. The substoichiometric dosage of the Al precursors ensured complete condensation and uniform incorporation, with the bulky spherosilicate forcing a separation between neighboring aluminum centers.

WO Nanowhiskers Decorating SiO Nanofibers: Lessons from SEM/TEM Growth to Large Scale Synthesis and Fundamental Structural Understanding.

Tungsten suboxide WO nanowhiskers are a material of great interest due to their potential high-end applications in electronics, near-infrared light shielding, catalysis, and gas sensing. The present study introduces three main approaches for the fundamental understanding of WO nanowhisker growth and structure. First, WO nanowhiskers were grown from γ-WO/-SiO nanofibers in a scanning electron microscope (SEM) utilizing a specially designed microreactor (μReactor).

Copper Phosphinate Complexes as Molecular Precursors for Ethanol Dehydrogenation Catalysts.

Nowadays, the production of acetaldehyde heavily relies on the petroleum industry. Developing new catalysts for the ethanol dehydrogenation process that could sustainably substitute current acetaldehyde production methods is highly desired. Among the ethanol dehydrogenation catalysts, copper-based materials have been intensively studied.

Reactions of permethyltitanocene tucked-in derivatives with carbon dioxide.

Both single tucked-in permethyltitanocene 1 and double tucked-in permethyltitanocene 2 react with excess CO by insertion into their Ti-CH bonds. The former one precipitates instantly a yellow carboxylate-tethered oligomer [3] which is insoluble in aprotic solvents and in a vacuum it sublimes as a monomer without decomposition. Computations for ≤ 4 optimised the structure of the monomer [3] and showed that open chain oligomers bound by dative O → Ti bonds were not sterically hindered.

Luminescent Cationic Group 4 Metallocene Complexes Stabilized by Pendant N-Donor Groups.

Cationic group 4 metallocene complexes with pendant imine and pyridine donor groups were prepared as stable crystalline [B(CF)] salts either by protonation of the intramolecularly bound ketimide moiety in neutral complexes [(η-CMe){η-CHCMeCMeC(R)═N-κ}MCl] (M = Ti, Zr, Hf; R = -Bu, Ph) by PhNMeH[B(CF)] to give [(η-CMe){η-CHCMeCMeC(R)═NH-κ}MCl][B(CF)] or by chloride ligand abstraction from the complexes [(η-CMe)(η-CHCMeCHCHN)MCl] (M = Ti, Zr) by Li[B(CF)]·2.5EtO to give [(η-CMe)(η-CHCMeCHCHN-κ)MCl][B(CF)]. Solid state structures of the new compounds were established by X-ray diffraction analysis, and their electrochemical behavior was studied by cyclic voltammetry.

Hydrodehalogenation of organohalides by EtSiH catalysed by group 4 metal complexes and B(CF).

Catalytic hydrodehalogenation (HDH) of aliphatic organohalides such as trifluorotoluenes by Et3SiH proceeds in the presence of readily available group 4 metal compounds: Cp'2MX2 (Cp' = η5-C5H5 or η5-C5Me5; X = F, Cl, or Me; M = Ti, Zr, or Hf), CpTiCl3 and TiCl4 with a catalytic amount of B(C6F5)3. The use of metallocenes in combination with the borane activator leads to a better selectivity of the reaction, i.e.

Morphology Control in AgCu Nanoalloy Synthesis by Molecular Cu(I) Precursors.

As nanoparticle preparation methods employing bottom-up procedures rely on the use of molecular precursors, the chemical composition and bonding of these precursors have a decisive effect on nanoparticle formation and their resulting morphology and properties. We synthesized the Cu(I) complexes [Cu(PPh)(bea)] (, bea = benzoate) and [Cu(PPh)(Hphta)] (, phta = phthalate) by reducing the corresponding Cu(II) mono- and dicarboxylates with triphenylphosphine. We characterized and by single-crystal X-ray diffraction analysis, elemental analyses, infrared and nuclear magnetic resonance spectroscopy, and mass spectrometry and obtained complete information about their structures in the solid state and in solution.

Ring Formation and Hydration Effects in Electron Attachment to Misonidazole.

We study the reactivity of misonidazole with low-energy electrons in a water environment combining experiment and theoretical modelling. The environment is modelled by sequential hydration of misonidazole clusters in vacuum. The well-defined experimental conditions enable computational modeling of the observed reactions.

Alumazene Reactivity with Quinolinols - Addition and Substitution Reactions on the Al3N3 Ring.

Molecular structures of two compounds obtained in reactions of alumazene [DippNAlMe]3 (1, Dipp = 2,6-i-Pr2C6H3) with substituted quinolinols have been elucidated by the single-crystal X-ray diffraction analysis. Quinolin-8-ol (Hq) provides a dinuclear complex [(DippNH)2Al2Me2(q)2] (2) with a central Al2O2 ring and five-coordinate Al atoms. The compound 2×THF crystallizes in the orthorhombic Pbca space group.

Hydrogenation of titanocene and zirconocene bis(trimethylsilyl)acetylene complexes.

Reactions following the addition of dihydrogen under maximum atmospheric pressure to bis(trimethylsilyl)acetylene (BTMSA) complexes of titanocenes, [(η5-C5H5-nMen)2Ti(η2-BTMSA)] (n = 0, 1, 3, and 4) (1A-1D), and zirconocenes, [(η5-C5H5-nMen)2Zr(η2-BTMSA)] (n = 2-5) (4A-4D), proceeded in diverse ways and, depending on the metal, afforded different products. The former complexes lost, in all cases, their BTMSA ligand via its hydrogenation to bis-1,2-(trimethylsilyl)ethane when reacted at 80 °C for a prolonged reaction time. For n = 0, 1, and 3, the titanocene species formed in situ dimerised via the formation of fulvalene ligands and two bridging hydride ligands, giving known green dimeric titanocenes (2A-2C).

New Adamantane-like Silicophosphate Cage and Its Reactivity toward Tris(pentafluorophenyl)borane.

The condensation reaction between PhSi(OC(O)CH) and OP(OSiMe) leads to elimination of CHC(O)OSiMe and the formation of the new silicophosphate cage molecule PhSiPO (1) with an adamantane-like core possessing four terminal P═O moieties and six O-SiPh-O bridging groups. Compound 1 was further reacted with the Lewis acid B(CF). We observed adduct formation by coordination through the P═O→B bonds and isolated and structurally characterized two new molecules.

Decamethyltitanocene hydride intermediates in the hydrogenation of the corresponding titanocene-(η-ethene) or (η-alkyne) complexes and the effects of bulkier auxiliary ligands.

H NMR studies of reactions of titanocene [Cp*Ti] (Cp* = η-CMe) and its derivatives [Cp*(η:η-CMeCH)TiMe] and [Cp*Ti(η-CH[double bond, length as m-dash]CH)] with excess dihydrogen at room temperature and pressures lower than 1 bar revealed the formation of dihydride [Cp*TiH] (1) and the concurrent liberation of either methane or ethane, depending on the organometallic reactant. The subsequent slow decay of 1 yielding [Cp*TiH] (2) was mediated by titanocene formed in situ and controlled by hydrogen pressure. The crystalline products obtained by evaporating a hexane solution of fresh [Cp*Ti] in the presence of hydrogen contained crystals having either two independent molecules of 1 in the asymmetric part of the unit cell or cocrystals consisting of 1 and [Cp*Ti] in a 2 : 1 ratio.

Hydrosilane-B(C6F5)3 adducts as activators in zirconocene catalyzed ethylene polymerization.

Hydrosilane-B(C6F5)3 adducts were found to activate zirconocene dihalides and generate ternary catalytic systems possessing moderate to high activity in ethylene polymerization to high density polyethylene (HDPE). The activation efficacy of the adducts increased with increasing hydride donor ability and decreased with steric crowding of the particular hydrosilane used. NMR investigation of the HSiEt3/B(C6F5)3/Cp*2ZrF2 system (Cp* = η(5)-C5Me5) revealed the formation of a stable intermediate [Cp*2ZrF(FSiEt3-κF)](+)[HB(C6F5)3](-), whereas a crucial role of the [HB(C6F5)3](-) anion as a hydride donor for generation of an active cationic zirconium hydride center was elucidated.

Evaluation of cytotoxic activity of titanocene difluorides and determination of their mechanism of action in ovarian cancer cells.

Background: Ovarian cancer is the seventh-most common cancer amongst women and the most deadly gynecologic cancer. Cisplatin based drugs are used in first line therapy, but resistance represents a major obstacle for successful treatment. In this study, we investigated the anticancer effects and mechanism of action of three titanocene difluorides, two bearing a pendant carbohydrate moiety (α-D-ribofuranos-5-yl) on their periphery and one without any substitution.

Heat-induced spinodal decomposition of Ag-Cu nanoparticles.

Solvothermal synthesis was used for Ag-Cu nanoparticle (NP) preparation from metallo-organic precursors. The detailed NP characterization was performed to obtain information about nanoparticle microstructure and both phase and chemical compositions. The resulting nanoparticles exhibited chemical composition inside a FCC_Ag + FCC_Cu two-phase region.

Displacement of ethene from the decamethyltitanocene-ethene complex with internal alkynes, substituent-dependent alkyne-to-allene rearrangement, and the electronic transition relevant to the back-bonding interaction.

The titanocene-ethene complex [Ti(II)(η(2)-C2H4)(η(5)-C5Me5)2] (1) with simple internal alkynes R(1)C≡CR(2) gives complexes [Ti(II)(η(2)-R(1)C≡CR(2))(η(5)-C5Me5)2] {R(1), R(2): Ph, Ph (3), Ph, Me (4), Me, SiMe3 (5), Ph, SiMe3 (6), t-Bu, SiMe3 (7), and SiMe3, SiMe3 (8). In contrast, alkynes with R(1) = Me and R(2) = t-Bu or i-Pr afford allene complexes [Ti(II)(η(2)-CH2=C=CHR(2))(η(5)-C5Me5)2] (11) and (12), whereas for R(2) = Et a mixture of alkyne complex (13A) and minor allene (13) is obtained. Crystal structures of 4, 6, 7 and 11 have been determined; the latter structure proved the back-bonding interaction of the allene terminal double bond.

Sonochemical precipitation of amorphous uranium phosphates from trialkyl phosphate solutions and their thermal conversion to UP2O7.

Insoluble amorphous precipitates containing uranyl and phosphate ions are obtained by sonication of solutions of three uranyl precursors, UO2(X)2, X=NO3, CH3COO, CH3C(O)CHC(O)CH3 (acetylacetonate, acac), in triesters of phosphoric acid, OP(OR)3, R=Me (trimethyl phosphate, TMP), Et (triethyl phosphate, TEP). TMP and TEP are used as high-boiling solvents and they serve also as a source of phosphate anions. Sonolysis experiments were carried out under flow of Ar at 40°C on a Sonics and Materials VXC 500W system (f=20 kHz, Pac=0.

Construction of larger molecular aluminophosphate cages from the cyclic four-ring building unit.

New molecular aluminophosphates of different nuclearity are synthesized by a stepwise process and structurally characterized. The alkane elimination reaction of bis(trimethylsiloxy)phosphoric acid, OP(OH)(OSiMe3)2, with trialkylalanes, AlR3 (R = Me, Et, (i)Bu), provides the cyclic dimeric aluminophosphates, [(AlR2{μ2-O2P(OSiMe3)2})2] (R = Me (1), Et (2), (i)Bu (3)). Unsymmetrically substituted cyclic aluminophosphonate [(AlMe2{μ2-O2P(OSiMe3)((c)Hex)})2] (cis/trans-4) is prepared by dealkylsilylation reaction of (c)HexP(O)(OSiMe3)2 with AlMe3.

Diethyl [4-(2,2':6',2''-terpyridine-4'-yl)phen-yl]phospho-nate.

The title compound, C25H24N3O3P, was obtained by catalytic phospho-nation of 4'-(4-bromphen-yl)-2,2':6',2''-terpyridine. The terpyridine moiety is nearly planar, the dihedral angles between the central and the outer rings being 4.06 (9) and 5.

Synthetic transformations of a pendant nitrile moiety in group 4 metallocene complexes.

Functional group transformations at the group 4 metallocene framework have been demonstrated, which have provided relatively straightforward access to otherwise synthetically challenging derivatives. The pendant nitrile group in Ti and Zr metallocene complexes of the type [(η(5)-C5Me5)(η(5)-C5H4CMe2CH2CN)MCl2] was converted into an intramolecularly bound ketimido moiety by alkylation, which took place not only at the nitrile, but also at the metal centre. The choice of an alkylating reagent (alkyl/aryl lithium, Grignard reagent) was crucial: e.

Synthesis of Organotitanium(IV) Fluoride Phosphates and the Crystal Structure of [(C5Me4Et)TiF(µ-F){µ-O2P(OSiMe3)2}]2.

The complexes [(C5Me4R)TiF(µ-F)µ-O2P(OSiMe3)2]2 [R = Me (1), Et (2)] were prepared from [(C5Me4R)TiF3]2, (R = Me, Et) and OP(OSiMe3)3. The molecular structure of 2 has been determined by single-crystal X-ray diffraction analysis. An eight-membered Ti2O4P2 metallacycle bridged by two fluorine ligands between two titanium centers is observed.

A structurally diverse series of aluminum chloride alkoxides [Cl(x)Al(mu-OR)(y)](n) (R = (n)Bu, (c)Hex, Ph, 2,4-(t)Bu2C6H3).

A diverse series of aluminum chloride alkoxides, [Cl(x)Al(mu-OR)(y)](n) (R = (n)Bu, (c)Hex, Ph, 2,4-(t)Bu(2)C(6)H(3)), was synthesized using the reactions of dichlorethylalane (EtAlCl(2)) with cyclohexanol ((c)HexOH), n-butanol ((n)BuOH), and phenols (PhOH and 2,4-(t)Bu(2)C(6)H(3)OH). Eight molecular products were isolated and structurally characterized. The dimeric [Cl(2)Al(mu-O(c)Hex)(2)AlCl(2)] (1) was the smallest oligomer isolated among the cyclohexanolate derivatives.

Alumazene adducts with pyridines: synthesis, structure, and stability studies.

Lewis acid-base adducts of the alumazene [2,6-(i-Pr)2C6H3NAlMe]3 (1) with pyridine (py) and 4-dimethylaminopyridine (dmap) were synthesized and structurally characterized: 1(py)2 (2), 1(py)3 (3), 1(dmap)2 (4), and 1(py)(dmap) (5). The bisadducts 2, 4, and 5 form the trans isomers. The trisadduct 3 exhibits an unexpected cis-cis isomer and can be prepared only in the presence of excess py.