Dendritic macromolecules containing several types of functional groups

Dendritic macromolecules containing several types of functional groups were successfully synthesized through divergent method. Poly(ethylene glycol) was functionalized using cyanuric chloride and it was reacted with p‐toluidine at room temperature and a macromolecule containing chloride and methyl functional groups (PEG‐Cl₂‐Me₂) was obtained. Substitution of chloride functional groups of PEG‐Cl₂‐Me₂ by hydroxyl functional groups led to a macromolecule containing methyl and hydroxyl functional groups (PEG‐Me₂‐OH₄). Hydroxyl functional groups of PEG‐Me₂‐OH₄ were reacted with cyanuric chloride and PEG‐Me₂‐Cl₈ was obtained. Finally, PEG‐Me₂‐Cl₈ was reacted with p‐aminophenol at room temperature and a macromolecule containing methyl, hydroxyl, and chloride functional groups (PEG‐Me₂‐(PhOH)₄‐Cl₄) was obtained. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Novel Supramolecular Square Grid-Like Structure: Synthesis and Characterization of [(Me3Sn)2CrO4]

Reactions of K₂Cr₂O₇ and K₂CrO₄ with Me₃SnCl yielded [(Me₃Sn)₂CrO₄] (1) and [(Me₃Sn)₂CrO₄?(Me₃SnOH)] (2), respectively, which were characterized by elemental analysis, ¹H-NMR spectroscopy, and an X-ray diffraction study. Compound 1 shows a novel square grid-like structure consisting of CrO₄ ^2? and Me₃Sn⁺ ions, whereas 2 exhibits a three-dimensional structure composed of CrO₄ ^2?, Me₃Sn⁺, and [(Me₃Sn)₂SnOH]⁺ ions.     

The formation of [RuCl(p-cymene)(Me2HPz)(PPh2OR)]Cl (Me2HPz=3, 5-dimethylpyrazole; R=H,Me and p-Tol) complexes from the cleavage of the P–N bond of a P-coordinated P(Me2Pz)Ph2 ligand by ROH molecules in a ruthenium(II) complex. Crystal structure of [RuCl(p-cymene)(Me2HPz)(PPh2OH)]Cl

The complex [RuCl₂(p-cymene)]₂ reacts with 1-(3,5-dimethyl)pyrazolyldiphenylphosphine (P(Me₂Pz)Ph₂) to give the complex RuCl₂(p-cymene)(P(Me₂Pz)Ph₂). This compound reacts with ROH molecules (R=H, Me and p-Tol) to give [RuCl(p-cymene)(Me₂HPz)(PPh₂OR)]Cl (R=H, Me and p-Tol) complexes, which contain both Me₂HPz and PPh₂OR coordinated molecules.     

Design of New Functional Materials Based on Complex Oxides with a Tunnel Structure of the Ramsdellite, Hollandite, and Ba2Ti9O20 Types

The phase relationships in binary, ternary, and more complex Me ₂ ⁺O–Me ²⁺O–Me ₂ ³⁺O₃–Me ⁴⁺O₂–TiO₂ systems (Me ⁺ = Li⁺, K⁺, Rb⁺, Cs⁺; Me ²⁺ = Mg²⁺, Sr²⁺, Ba²⁺, Zn²⁺; Me ³⁺ = Al³⁺, Fe³⁺, Ga³⁺; Me ⁴⁺ = Sn⁴⁺, Zr⁴⁺) are investigated in the concentration regions corresponding to the compositions of titanates with a tunnel structure: Li₂(Me ²⁺,Me ³⁺) _y (Me ⁴⁺,Ti)₄O₈ ramsdellites, (Me ⁺,Me ²⁺) _x (Me ²⁺,Me ³⁺) _y (Me ⁴⁺,Ti)₈O₁₆ hollandites, and (Ba,Me ²⁺)₂(Me ⁴⁺,Ti)₉O₂₀ phases. The homogeneity regions of the solid solutions with the above structures are determined, and their crystal chemical characteristics, phase transformations, and thermal and electrical properties are studied. The results obtained and the data available in the literature are analyzed and generalized. The general approaches to the prediction of changes in the structure and properties of the studied titanates with a variation in the chemical composition due to isomorphous substitutions in different structural positions of the crystal lattice are discussed.     

Assembly, Fluorescence Properties and Antitumor Activity of Novel Silver(I) Cyanide Supramolecular Coordination Polymer Based on Trans-1,2-bis(4-pyridyl)ethene and Me3SnCl

A bimetallic supramolecular coordination polymer; {[(Me₃Sn)₈Ag₄(OH)₄(CN)₈(tbpe)](tbpe)} _n , 1, was obtained by the reaction in situ of K₂[Ag(CN)₂] with Me₃SnCl and trans-1,2-bis(4-pyridyl)ethene (tbpe) in a H₂O/MeCN/NH₃ solvent. The structure of 1 consists of discrete puckered tetranuclear chains comprising {[(Me₃Sn)₄Ag₂(OH)₂(CN)₄]₂(tbpe)} in addition to one template free tbpe ligand. In these chains, the bridging hydroxyl group and the bipodal tbpe ligand are used to give two novel spacers based on the organometallic Me₃Sn unit; i.e., a longer spacer [–CN–(Me₃)Sn–O(H)–(Me₃)Sn–L–(Me₃)Sn–O(H)–(Me₃)Sn–NC–] with a separation distance of 31.29 Å, and a relatively shorter spacer [–CN–(Me₃)Sn–O(H)–(Me₃)Sn–NC–] with a separation distance of 14.431 Å. Supramolecular interactions such as hydrogen bonding, π–π stacking, cation···π interactions, play a prominent role in the assembly of this compound. The structure of the SCP was also investigated by FTIR and electronic absorption spectra and thermal analysis and the data are compared to the prototype compounds. The SCP 1 exhibits strong fluorescence in acetonitrile and shows specific in vitro antitumor activity against human breast cancer cell line, MCF7.     

Novel Supramolecular Square Grid-Like Structure: Synthesis and Characterization of [(Me3Sn)2CrO4]

Reactions of K₂Cr₂O₇ and K₂CrO₄ with Me₃SnCl yielded [(Me₃Sn)₂CrO₄] (1) and [(Me₃Sn)₂CrO₄(Me₃SnOH)] (2), respectively, which were characterized by elemental analysis, ¹H-NMR spectroscopy, and an X-ray diffraction study. Compound 1 shows a novel square grid-like structure consisting of CrO₄ ^2– and Me₃Sn⁺ ions, whereas 2 exhibits a three-dimensional structure composed of CrO₄ ^2–, Me₃Sn⁺, and [(Me₃Sn)₂SnOH]⁺ ions.     

On the formation of permethylcyclopolysilanes in the würtz-type reaction of Me2SiCl2: The influence of solvent and complexing agent

Permethylcyclopolysilanes are most often prepared by Würtz-type coupling of Me₂SiCl₂ with Na K alloy in THI: When nonpolar solvents like benzene were used, only linear polysilanes (Me₂Si)_n were produced, but the addition of a catalytic amount of crown ether 18-crown-6 was found to increase significantly the amount of cyclic oligomers. The ratio of (Me₂Si)₆ to (Me₂Si)₅ decreased from 18:1 to 6:1 in the presence of crown ether in a typical synthesis in THF. An explanation based on solvated electron theory has been proposed.     

Formation of a binuclear titanocene hydride–magnesium hydride carbyl-bridged complex in the (C5Me4Ph)2TiCl2/Mg/THF system

The reduction of (C₅Me₄Ph)₂TiCl₂ by magnesium in tetrahydrofuran affords a mixture of the diamagnetic doubly tucked-in titanocene complex (C₅Me₄Ph)[C₅Me₂(CH₂)₂Ph]Ti (1), the paramagnetic trinuclear Ti–Mg–Ti hydride bridged complex [(C₅Me₄Ph)₂Ti(μ-H)₂]₂Mg (2) and the paramagnetic binuclear titanocene hydride–magnesium hydride complex (C₅Me₄Ph)[C₅Me₄(o-C₆H₄)]Ti(μ-H)₂Mg(THF)₂ (3). The X-ray diffraction analysis of 3 revealed that the magnesium atom forms the σ-bond to the ortho-carbon atom of one of the phenyl rings and binds 2 molecules of THF.     

Immobilized Me2Si(C5Me4)(N‐tBu)TiCl2/(nBuCp)2ZrCl2 hybrid metallocene catalyst system for the production of poly(ethylene‐co‐hexene) with pseudo‐bimodal molecular weight and inverse comonomer distribution

Me₂Si(C₅Me₄)(N‐tBu)TiCl₂, (nBuCp)₂ZrCl₂, and Me₂Si(C₅Me₄)(N‐tBu)TiCl₂/(nBuCp)₂ZrCl₂ catalyst systems were successfully immobilized on silica and applied to ethylene/hexene copolymerization. In the presence of 20 mL of hexene and 25 mg of butyloctyl magnesium in 400 mL of isobutane at 40 bar of ethylene, Me₂Si(C₅Me₄)(N‐tBu)TiCl₂ immobilized catalyst afforded poly(ethylene‐co‐hexene) with high molecular weight ([η] = 12.41) and high comonomer content (%C₆ = 2.8%), while (nBuCp)₂ZrCl₂‐immobilized catalyst afforded polymers with relatively low molecular weight ([η] = 2.58) with low comonomer content (%C₆ = 0.9%). Immobilized Me₂Si(C₅Me₄)(N‐tBu)TiCl₂/(nBuCp)₂ZrCl₂ hybrid catalyst exhibited high and stable polymerization activity with time, affording polymers with pseudo‐bimodal molecular weight distribution and clear inverse comonomer distribution (low comonomer content for low molecular weight polymer fraction and vice versa). The polymerization characteristics and rate profiles suggest that individual catalysts in the hybrid catalyst system are independent of each other. POLYM. ENG. SCI., 47:131–139, 2007. © 2007 Society of Plastics Engineers     

Catalytic hydrogen wave in presence of dimethydithiocarbamate and cobalt(II)

The presence of dimethyldithiocarbamate (Me₂DTC) in a medium containing ammonia (borax-NH₄Cl and NH₄OH-NH₄Cl buffer) and cobalt(II) gives rise to a catalytic hydrogen wave. The effects of Me₂DTC and cobalt(II) concentrations, mercury column height and addition of gelatin on the catalytic hydrogen wave are discussed. A mechanism for this wave is proposed in which the H₃O⁺ is reduced on Co(0) stabilized by the Me₂DTC at the mercury surface.     

Catalytic prewaves of cobalt(II) in presence of dimethyldithiocarbamate

Two well-defined prewaves of cobalt(II) in the presence of dimethyldithiocarbamate (Me₂DTC) in a medium containing ammonia (borax-NH₄Cl and NH₄OH-NH₄Cl buffer) are observed. The effect of gelatine, Me₂DTC, cobalt(II), ammonium hydroxide and ammonium chloride concentration, mercury reservoir height, buffer capacity, pH and temperature on the prewaves are described. In addition, the characteristics of the current-time and electrocapillary curves are shown. This allows to propose a mechanism where the cobalt(II) prewaves are produced by cobalt(II) complexes with Me₂DTC. In these complexes, the cobalt(II) and Me₂DTC are in the relationship 1:1 and 1:2 for the first and second prewave respectively. A value of the rate constant for the formation of the first prewave catalytic complex of 6.0 x 10⁶ lmol^?1 s^?1 has been found at 20°C.     

Experimental and DFT calculated structure of the diruthenium(2.5) complex [(Me3TACN)Ru(μ-Cl)3Ru(Me3TACN)](PF6)2

The diruthenium(2.5) complex [(Me₃TACN)Ru(μ-Cl)₃Ru(Me₃TACN)]-(PF₆)₂, Me₃TACN = 1,4,7-trimethyl-1,4,7-triazacyclononane, has been crystallized for structural characterization. The results are reproduced by density functional theory (DFT) calculations and confirm the sensitivity of the central Ru(μ-Cl)₃Ru core to contacts between the Cl bridging atoms and the co-ligands. The singly occupied MO is characterized as a σ* MO involving the metal d_z² orbitals and a small halide contribution by DFT calculations and EPR.     

Comparative study of propylene polymerization using Me2Si(RInd)2ZrCl2/SiO2-SMAO/AlR3 and Me2Si(RInd)2ZrCl2/MAO (R = Me, H)

A mechanistic analysis of propylene polymerization was performed, in which the catalyst system was Me₂Si(R¹Ind)₂ZrCl₂/SMAO/AlR₃² (in situ supported catalyst onto MAO-modified silica) or Me₂Si(R¹Ind)₂ZrCl₂/MAO (homogeneous), where R¹ = H or CH₃, cocatalyzed by AlR₃² = TEA (triethylaluminum), IPRA (isoprenylaluminum), or TIBA (triisobutylaluminum). The catalyst activity of the homogeneous system Me₂Si(2-Me-Ind)₂ZrCl₂/MAO was almost 8 times higher than that observed for Me₂Si(Ind)₂ZrCl₂/MAO (38 vs 4.6 kg PP/g cat h), while the polypropylene molar mass was 3 times higher (M_w: 93 vs 34 kg/mol). Conversely, the in situ supported systems Me₂Si(Ind)₂ZrCl₂/SMAO/AlR₃ and Me₂Si(2-Me-Ind)₂ZrCl₂/SMAO/AlR₃ showed similar activities, ranging from 0.2 to 1.5 kg PP/g cat h. The molar mass of the resulting polymers prepared using the in situ procedure was dependent on the AlR₃ nature and on the Al/Zr ratio. Generally, the heterogeneous catalysts produced PP with higher molecular weights than that obtained with homogeneous ones. The influence of the alkylaluminum, used as the cocatalyst, on the chain-transfer termination reaction to the alkyl compound was evident from the activity and the molecular weight of the produced polymers.     

Lead(II) in a sulfur-rich environment: Synthesis and molecular structure of the first dinuclear bis(mercaptoimidazolyl)methane complex

The first dinuclear bis(mercaptoimidazolyl)methane metal complex, the lead(II) derivative [Pb₂(Bmm^Me)₅](ClO₄)₄, has been prepared and fully characterized using a combination of analytical and spectroscopic techniques. X-ray crystallography confirmed the presence in the solid state of two dicationic [Pb(Bmm^Me)₂]²⁺ fragments bridged by the fifth Bmm^Me ligand, which uses an unprecedented unidentate:bidentate (μ-κ¹-S:κ²-S,S) coordination mode to link the two metal centers.     

Synthesis and crystal structure of the singly tucked-in derivative of bis(phenyltetramethylcyclopentadienyl)titanium

Thermolysis of [TiMe₂(η⁵-C₅Me₄Ph)₂] (4) at 145 °C for 5 h afforded the singly tucked-in paramagnetic titanocene [Ti(III)(η⁵-C₅Me₄Ph){η⁵:η¹-C₅Me₃Ph(CH₂)}] (9). In distinction to the singly tucked-in permethyltitanocene [Ti(III)(η⁵-C₅Me₅){η⁵:η¹-C₅Me₄(CH₂)}] (1) which was found crystallographically disordered [J.M. Fischer, W.E. Piers, V.G. Young, Jr., Organometallics 15 (1996) 2410] the single crystal X-ray diffraction analysis of 9 afforded molecular parameters with nearly by one order better precision as measured by esd-values.     

Ca(BH4)2 as a simple tool for the preparation of thorium and uranium metallocene borohydride complexes: First synthesis and crystal structure of (C5Me5)2Th(η3-H3BH)2

Calcium borohydride allows for the high-yielding synthesis of (C₅Me₅)₂An(η³-H₃BH)₂ (An = Th, U) by reaction with (C₅Me₅)₂AnCl₂ (An = Th, U). While a preparative synthesis of (C₅Me₅)₂U(η³-H₃BH)₂ has been previously reported in the literature using K(C₅Me₅) and U(BH₄)₄, the use of Ca(BH₄)₂ is higher yielding and mild. Full characterization of the novel compound (C₅Me₅)₂Th(η³-H₃BH)₂ is presented.     

The synthesis of (η5-cyclopentadienyl)titanium(IV) alkoxides by alcoholysis of the Ti–π-ligand bond in permethyl η3:η4-allyldiene-(η5-cyclopentadienyl)titanium(II)

The η³:η⁴-allyldiene-(η⁵-cyclopentadienyl)titanium(II) complex [Ti(η⁵-C₅Me₅){η³:η⁴-C₅Me₃(CH₂)₂}] (1) reacts with three molar equivalents of substituted propargylic alcohols FcCCCMe₂(OH) (2a) and PhCCCH₂OH (2b) at elevated temperature to give (η⁵-pentamethylcyclopentadienyl)titanium(IV) alkoxides [Ti(η⁵-C₅Me₅)(FcCCCMe₂O-κO)₃] (3a) and [Ti(η⁵-C₅Me₅)(PhCCCH₂O-κO)₃] (3b), respectively. The crystal structure of 3a has been determined by single-crystal X-ray diffraction.     

Metal-assisted syntheses and NMR characterization of square-planar Pd(II) and Pt(II) complexes with tridentate nitrogen-donor chelate ligands

The complexes [PtCl(NNN^H)](OTf) (1^H), [PdCl(NNN^H)](OTf) (2^H), [PdCl(NNN^Me)](OTf) (2^Me), [PdMe(NNN^H)](OTf) (3^H), [PdMe(NNN^Me)](OTf) (3^Me) and [PdMe(NNN^Ph)](OTf) (3^Ph) {NNN^H = (pyridin-2-ylmethylene)-quinolin-8-yl-amine; NNN^Me = (1-pyridin-2-yl-ethylidene)-quinolin-8-yl-amine; NNN^Ph = (phenyl-pyridin-2-yl-methylene)-quinolin-8-yl-amine} were prepared by reacting a stoichiometric methanolic mixture of 8-aminoquinoline and an ortho-substituted aldehydo- or keto-pyridine {2-pyridinecarboxaldehyde, 2-acetylpyridine or 2-benzoylpyridine} with the proper Pt(II) or Pd(II) precursor in methanol. In the case of the 2 ^Me derivative, the addition of a stoichiometric amount of a Ag(I) salt to the reaction mixture was necessary to obtain the desired product. Information about the formation of these complexes are reported. In particular, NMR experiments allowed to observe the different reactivity of 8-aminoquinoline towards aldehydo- and keto-pyridines and the formation of the emiaminal ligand pyridin-2-yl-(quinolin-8-ylamino)-methanol NNN(H₂O)^H 4. Finally, the methanesulphonato-complex [Pd(η¹-OSO₂CH₃)(NNN^Me)](OTf) (5^Me) was obtained by reacting the chloro-derivative 2^Me with a stoichiometric amount of AgSO₃CH₃ in nitromethane.     

[Re(NBH2SBH3)(Me2PhP)(Et2dtc)]2 — a novel rhenium dimer with the unusual bridging (NBH2SBH3)4− ligand

The title compound is formed during the reaction of [ReN(Me₂PhP)(Et₂dtc)₂] (Me₂PhP=dimethylphenylphosphine, Et₂dtc⁻=diethyldithiocarbamate) with excess BH₃ in tetrahydrofurane. Two Re^V atoms are linked by two (NBH₂SBH₃)⁴⁻ units which act as three-dentate ligands via N, S and H forming an eight-membered metallacycle with additional coordination of an hydrido H atom trans to the nitrogen atom. The ReN multiple bond length is 1.70(1) Å which is only slightly longer than in the starting compound [ReN(Me₂PhP)(Et₂dtc)₂] (1.666(6) Å).