STEREOREGULARITY OF POLY (METHYL METHACRYLATE) OBTAINED WITH CHIRAL ANIONIC COMPLEX INITIATOR

The stereoregular polymerization of methyl methacrylate (MMA) have been investigatedwith chiral anionic complex initiator[FILi-(-)SP]in toluene, THF and toluene/THF [1/1(v/v)]. The tacticities of PMMAs obtained in the three solvents have been found to be mainly asyndiotactic triads(s-PMMA)with content of 72.3, 67.7 and 71.4%,respectively.     

Chirale Gallium‐ und Indium‐Alkoxometallate

Chiral Gallium and Indium Alkoxometalates Li₂(S)‐BINOLate ((S)‐BINOL = (S)‐(–)‐2,2′‐Dihydroxy‐1,1′‐binaphthyl) generated by dilithiation of (S)BINOL with two equivalents ⁿBuLi was reacted with GaCl₃ und InCl₃ in THF to the alkoxometalates [{Li(THF)₂}{Li(THF)}₂{Ga((S)‐BINOLate)₃}] ( 1 ) and [{Li(THF)₂}₂{Li(THF)}{In((S)‐BINOLate)₃}] · [{Li(THF)₂}{Li(THF)}₂{In((S)‐ BINOLate)₃}]₂ ( 3 ), respectively. 1 and 3 crystallize from THF/toluene mixtures as 1 · 2 toluene and 3 · 8 toluene. The treatment of PhCH₂GaCl₂ with Li₂(S)‐BINOLate in THF under reflux, followed by recrystallization of the product from DME gives the gallate [{Li(DME)}₃{Ga((S)BINOLate)₃}] · 1.5 THF ( 2 · 1.5 THF). 1 – 3 were characterized by NMR, IR and MS techniques. In addition, 1 · 2 toluene, 2 · 1.5 THF and 3 · 8 toluene were investigated by X‐ray structure analyses. According to them, a distorted octahedral coordination sphere around the group 13 metal was formed, built‐up by three BINOLate ligands. The three Li⁺ counter ions act as bridging units by metal‐oxygen coordination. The coordination sphere of the Li⁺ ions was completed, depending on the available space, by one or two THF ligands ( 1 · 2 toluene, 3 · 8 toluene) and one DME ligand ( 2 · 1.5 THF), respectively. The sterical dominance of the BINOLate ligands can be shown by the almost square‐planar coordination of the Li⁺ ions in 2 · 1.5 THF giving a small twisting angle of only 17°.     

Micellar structures of poly(styrene-b-4-vinylpyridine)s in THF/toluene mixtures and their functionalization with gold

The effects of the block copolymer composition and the solvent selectivity on the micellar morphologies of poly(styrene- b-4-vinylpyridine)s (PS- b-P4VPs) and their functionalizations with gold were studied in 10 mg/mL solutions using small-angle X-ray scattering and transmission electron microscopy (TEM). The solvent selectivity for the PS block was controlled by toluene/tetrahydrofuran (THF) mixtures in which toluene and THF are selective for PS and nonselective, respectively. The micellar structure was strongly dependent on phi (wt % toluene in toluene/THF mixture) and the composition of the block copolymers. PS(12K)- b-P4VP(11.8K) (symmetric) showed spherical micelles in the entire range of phi except phi = 0 (THF, nonselective solvent). PS(3.3K)- b-P4VP(18.7K) (asymmetric, longer P4VP) showed multiple morphologies with transitions from spheres to cylinders and finally to vesicles with an increase in phi. PS(19.6K)- b-P4VP(5.1K) (asymmetric, longer PS) showed spherical micelles only at the narrow ranges of 90 wt % 相似文献   

Synthesis and structural characterization of beta-diketiminate-lanthanide amides and their catalytic activity for the polymerization of methyl methacrylate and epsilon-caprolactone

The synthesis and catalytic activity of lanthanide monoamido complexes supported by a beta-diketiminate ligand are described. Donor solvents, such as DME, can cleave the chloro bridges of the dinuclear beta-diketiminate ytterbium dichloride {[(DIPPh)2nacnac]YbCl(mu-Cl)3Yb[(DIPPh)2nacnac](THF)} (1) [(DIPPh)2nacnac = N,N-diisopropylphenyl-2,4-pentanediimine anion] to produce the monomeric complex [(DIPPh)2nacnac]YbCl2(DME) (2) in high isolated yield. Complex 2 is a useful precursor for the synthesis of beta-diketiminate-ytterbium monoamido derivatives. Reaction of complex 2 with 1 equiv of LiNPri2 in THF at room temperature, after crystallization in THF/toluene mixed solvent, gave the anionic beta-diketiminate-ytterbium amido complex [(DIPPh)2nacnac]Yb(NPri2)(mu-Cl)2Li(THF)2 (3), while similar reaction of complex 2 with LiNPh2 produced the neutral complex [(DIPPh)2nacnac]Yb(NPh2)Cl(THF) (4). Recrystallization of complex 3 from toluene solution at elevated temperature led to the neutral beta-diketiminate-lanthanide amido complex [{(DIPPh)2nacnac}Yb(NPri2)(mu-Cl)]2 (5). The reaction medium has a significant effect on the outcome of the reaction. Complex 2 reacted with 1 equiv of LiNPri2 and LiNC5H10 in toluene to produce directly the neutral beta-diketiminate-lanthanide amido complexes 5 and [{(DIPPh)2nacnac}Yb(NC5H10)(THF)(mu-Cl)]2 (6), respectively. These complexes were well characterized, and their crystal structures were determined. Complexes 4-6 exhibited good catalytic activity for the polymerization of methyl methacrylate and epsilon-caprolactone.     

The effect of coordinating and non-coordinating additives on the transport properties in ionic liquid electrolytes for lithium batteries

In the present study we expand our analysis of using two contrasting organic solvent additives (toluene and THF) in an ionic liquid (IL)/Li NTf(2) electrolyte. Multinuclear Pulsed-Field Gradient (PFG) NMR, spin-lattice (T(1)) relaxation times and conductivity measurements over a wide temperature range are discussed in terms of transport properties and structuring of the liquid. The conductivity of both additive samples is enhanced the most at low temperatures, with THF slightly more effective than toluene. Both the anion and lithium self-diffusivity are enhanced in the same order by the additives (THF > toluene) while that of the pyrrolidinium cation is marginally enhanced. (1)H spin-lattice relaxation times indicate a reasonable degree of structuring and anisotropic motion within all of the samples and both (19)F and (7)Li highlight the effectiveness of THF at influencing the lithium coordination within these systems.     

Solvent-dependent stereoselectivity in a Still-Wittig rearrangement: an experimental and ab initio study

[see reaction]. The Still-Wittig rearrangement gave opposite selectivities for (Z:E)-alkenes in THF (3:1) vs toluene (1:3) in the synthesis of serine-proline dipeptide amide isosteres. Four transition states leading to (Z)-and (E)-alkenes with THF and without (representing toluene) were identified by ab initio calculations at the 3-21G* level. The calculated (Z:E)-ratios with THF (4.7:1) and without THF (1:3.2) suggested that the transition state geometries and energies were well-represented by the calculations.     

Lithium amidohydridoaluminates

The amidohydridometalates [Li(THF)4][HAl(NPh2)3] (1), [Li(DME)3][HAl(N(CH2Ph)2)3] (2), and [((THF)3Li)-(H2Al(NcHex2)2)].0.5toluene (3.0.5toluene; cHex = C6H11) have been prepared by reaction of the corresponding amines with LiAlH4 in THF. For 2 recrystallization from DME is required to obtain crystals, suitable for X-ray diffraction. The new compounds have been characterized by elemental analyses, IR, NMR, and MS techniques, and X-ray structure analyses. According to this the anions of 1, 2, and 3x0.5toluene possess distorted tetrahedral coordination spheres. In 3x0.5toluene a Li...H contact of 184(4) pm was detected to complete the tetrahedral coordination of the Li+ center.     

Contrasting solvent and capping ligand effects directing the photochemistry of uranyl(VI) Schiff base complexes

Photolysis of the uranyl(VI) Schiff base complex UO2(tBu4-salphen)(THF) (1a) with cobaltocene in THF affords [Cp2Co][UO2(tBu4-salphen)(OH)] (2) in high yield while irradiation in toluene yields no reaction. Electronic emission spectra of 1a reveal a large Stokes' shift in toluene similar to that observed in the free ligand, while in THF the structural rearrangement responsible for this shift is blocked. Instead, the ligand-centered excited state is redirected to the uranyl(VI) center by way of energy transfer, thus generating 2 from the intramolecular activation of a coordinated THF molecule.     

Further Studies on the Anionic Copolymerization of Styrene and Glycidyl Methacrylate in Toluene

Sequential anionic copolymerization of styrene and glycidyl methacrylate (GMA) was performed with the protection of argon under normal pressure, where styrene, GMA, toluene, THF, n-butyllithium and a small amount of lithium chloride (LiCl) were used as first monomer, second monomer, solvent, polar reagent, initiator and additive, respectively. Polystyrene-b-poly(glycidyl methacrylate) diblock copolymers (PS-b-PGMA) with well-defined structure and narrow molecular weight distribution were prepared by the copolymerization reaction of poly(styryl)lithium with GMA under certain temperatures. The copolymers were characterized using gel permeation chromatography (GPC), ¹H-NMR, ¹³C-NMR, thin layer chromatography (TLC) and hydrochloric acid-dioxane argentimetric methods. The effects of additives, copolymerization temperature and THF dosage on the copolymerization were studied. No chain transfer reaction of anionic polymerization of styrene in toluene was observed. Slightly broader molecular weight distribution of PS-b-PGMA was observed with the increase the GMA repeat units. Using THF/toluene blend solvent could reduce the polydispersity index (M _w /M _n ) and dissolve the copolymer better than toluene alone. Lower temperature (< -40°C) and LiCl are required to prepare PS-b-PGMA with narrower molecular weight distribution.     

Regio- and stereoselective lithiation of 2,3-diphenylaziridines: a multinuclear NMR investigation

The alpha-lithiation-trapping sequence of trans-N-alkyl-2,3-diphenylaziridines (s-BuLi or s-BuLi/TMEDA), taking place with a stereochemistry which dramatically depends on the solvent coordinating ability (inversion of configuration in THF and retention in toluene), has been carefully investigated. 1H,13C, and 7Li multinuclear NMR investigations at low temperature suggest that two differently configured lithiated aziridines (monomeric cis-1-Li in THF and dimeric trans-1-Li in toluene) are involved.     

Alkaline earth metal complexes of a phosphine-borane-stabilized carbanion: synthesis, structures, and stabilities

The reaction between either MgI2 or CaI2 and 2 equiv of [(Me3Si)2{Me2(H3B)P}C]K (2) in toluene gives the corresponding organo-alkaline earth metal compounds [(Me3Si)2{Me2(H3B)P}C]2M in moderate to good yields [M = Mg (3), Ca (4)]. Compound 3 crystallizes solvent-free, whereas X-ray quality crystals of 4 could not be obtained in the absence of coordinating solvents; crystallization of 4 from cold methylcyclohexane/THF gives the solvate [(Me3Si)2{Me2(H3B)P}C]2Ca(THF)4 (4a). The corresponding heavier alkaline earth metal complexes [(Me3Si)2{Me2(H3B)P}C]2M(THF)5 [M = Sr (7), Ba (8)] are obtained from the reaction between MI2 and 2 equiv of 2 in THF, followed by recrystallization from cold methylcyclohexane/THF. Compound 3 degrades over a period of several weeks at room-temperature both in the solid state and in toluene solution to give the free phosphine-borane (Me3Si)2{Me2(H3B)P}CH (5) as the sole phosphorus-containing product. In addition, compounds 3, 4, and 4a react rapidly with THF in toluene solution, yielding 5 as the sole phosphorus-containing product; in contrast, compounds 7 and 8 are stable toward this solvent.     

Synthesis, structure and magnetic behavior of five-coordinate bis(iminopyrrolyl) complexes of cobalt(II) containing PMe3 and THF ligands

The new bis-iminopyrrolyl five-coordinate Co(II) complexes [Co(kappa (2) N, N'-NC 4H 3C(R)N-2,6- (i)Pr 2C 6H 3) 2(PMe 3)] (R = H 3a; Me 3b) were synthesized in high yields (ca. 80-90%), using THF and diethyl ether as solvents, respectively, by (a) treatment of CoCl 2(PMe 3) 2 with the corresponding iminopyrrolyl Na salts ( Ie or If) or (b) reaction of anhydrous CoCl 2 and PMe 3 with Ie or If. A third route was tested, involving the addition of excesses of PMe 3 to the complexes [Co(kappa (2) N, N'-NC 4H 3C(R)N-2,6- (i)Pr 2C 6H 3) 2] (R = H 1e; Me 1f), which was only successful for the synthesis of 3a, in lower yields (ca. 30%). The synthesis of 3b in THF was unfruitful because of the kinetic competition of the solvent, giving rise to mixtures of 1f and its coordinated THF adduct 4b. The synthesis of the new bis-iminopyrrolyl five-coordinate Co(II) complexes [Co(kappa (2) N, N'-NC 4H 3C(R)N-2,6- (i)Pr 2C 6H 3) 2(THF)] (R = H 4a; Me 4b) were carried out in high yields (ca. 80-90%) by the reaction of CoCl 2(THF) 1.5 with the corresponding iminopyrrolyl Na salt. All the compounds have been characterized by X-ray diffraction, with 3a and 3b showing axially compressed trigonal bipyramidal geometry (with the PMe 3 ligand lying on the equatorial plane), whereas complexes 4a and 4b exhibit distorted square pyramidal geometries with the THF molecule occupying the axial position. Complex 4a shows clearly a compressed geometry, but for complex 4b, two polymorphs were characterized, exhibiting molecules with different Co-O (THF) bond lengths, one of them being compatible with an elongated form. Magnetic measurements either in the solid or in the liquid phases indicate that complexes 3a and 3b have low-spin ground states ( S = 1/2). In toluene solution, the geometry is fully confirmed by EPR data, which further indicates a d x (2) - y (2) /d xy ground state. However, compounds 4a and 4b behave unusually because they show magnetic moments that are compatible with high-spin ground states ( S = 3/2) in the solid state, but conform to low-spin ground states ( S = 1/2) when both complexes are dissolved in toluene solutions. The low-spin ground states in toluene solution are confirmed by EPR spectroscopy, which further supports, for complexes 4a and 4b, an axially elongated square pyramidal geometry and a d z (2) ground state. Thus the change in the ground-state and, consequently, in the geometry of complexes 4a and 4b from solid state to toluene solution might be a consequence of the elongation of the Co-O(THF) bond length. DFT studies performed on complexes 3 and 4 corroborate their different structure and magnetic behaviors and verify, for the latter complexes, the structural differences observed in the solid state and in toluene solution.     

Stereospecific polymerization of o-methoxystyrene by anionic initiators

o-Methoxystyrene was polymerized with n-butyllithium (n-BuLi), Na naphthalene, and K dispersion as initiators in tetrahydrofuran (THF) and toluene. The stereoregularity of the polymer was investigated by means of the NMR spectroscopy. The methoxy resonance of the spectrum split into ten components due to the tactic pentads. It was found by x-ray examination that the polymer obtained by n-BuLi in toluene at ?45°C was crystalline and highly isotactic. In THF, the stereospecificity of the polymerization was independent of the initiator, and the isotacticity of the polymer increased with increasing reaction temperature. In toluene, the stereospecificity depended on the initiator; i.e., n-BuLi gave a polymer with higher isotacticity than that given by phenylsodium. The fraction of isotactic triad of the polymer obtained by n-BuLi in toluene at ?78°C was more than 90%, but 50% at 50°C. The presence of ca. 1% THF in toluene led to a steep decrease in the isotacticity even at ?78°C. The tacticity of the polymer given by Na naphthalene was not affected by the existence of NaB(C₆H₅)₄ in THF. The polymerization in THF could be explained by Bovey's “single σ” process, while a penultimate effect was observed in the polymerization by n-BuLi in toluene.     

Zirconium and hafnium complexes containing bidentate diarylamido-phosphine ligands

The first examples of mononuclear, structurally characterized triarylphosphine complexes of zirconium and hafnium are reported. The metathetical reactions of MCl4(THF)2 (M = Zr, Hf) with [iPrNP]Li(THF)2 ([iPrNP]- = N-(2-(diphenylphosphino)phenyl)-2,6-diisopropylanilide) or [MeNP]Li(THF)2 ([MeNP]- = N-(2-(diphenylphosphino)phenyl)-2,6-dimethylanilide) in toluene at -35 degrees C produced the corresponding [iPrNP]MCl3(THF) and [MeNP]2MCl2, respectively, in high yield. In contrast, attempts to prepare [MeNP]MCl3(THF) and [iPrNP]2MCl2 led to the concomitant formation of mono- and bis-ligated complexes, from which purification proved rather ineffective. The solution and solid-state structures of [iPrNP]MCl3(THF) and [MeNP]2MCl2 were studied by multinuclear NMR spectroscopy and X-ray crystallography. The geometry of these six-coordinate complexes is best described as a distorted octahedron in which the chloride ligands in [iPrNP]MCl3(THF) adopt a virtually meridional coordination mode whereas those in [MeNP]2MCl2 are trans to each other.     

Synthesis, characterization and reactivity of heteroleptic rare earth metal bis(phenolate) complexes

The synthesis, characterization and reactivity of heteroleptic rare earth metal complexes supported by the carbon-bridged bis(phenolate) ligand 2,2'-methylene-bis(6-tert-butyl-4-methyl-phenoxo) (MBMP(2-)) are described. Reaction of (C(5)H(5))(3)Ln(THF) with MBMPH(2) in a 1 : 1.5 molar ratio in THF at 50 degrees C produced the heteroleptic rare earth metal bis(phenolate) complexes (C(5)H(5))Ln(MBMP)(THF)(n) (Ln = La, n = 3 (); Ln = Yb (), Y (), n = 2) in nearly quantitative yields. The residual C(5)H(5)(-) groups in complexes to can be substituted by the bridged bis(phenolate) ligands at elevated temperature to give the neutral rare earth metal bis(phenolate) complexes, and the ionic radii have a profound effect on the structures of the final products. Complex reacted with MBMPH(2) in a 1 : 0.5 molar ratio in toluene at 80 degrees C to produce a dinuclear complex (MBMP)La(THF)(mu-MBMP)(2)La(THF)(2) () in good isolated yield; whereas complexes and reacted with MBMPH(2) under the same conditions to give (MBMP)Ln(MBMPH)(THF)(2) (Ln = Yb (), Y ()) as the final products, in which one hydroxyl group of the phenol is coordinated to the rare earth metal in a neutral fashion. The reactivity of complexes and with some metal alkyls was explored. Reaction of complex with 1 equiv. of AlEt(3) in toluene at room temperature afforded unexpected ligand redistributed products, and a discrete ion pair ytterbium complex [(MBMP)Yb(THF)(2)(DME)][(MBMP)(2)Yb(THF)(2)] () was isolated in moderate yield. Furthermore, reaction of complex with 1 equiv. of ZnEt(2) in toluene gave a ligand redistributed complex [(mu-MBMP)Zn(THF)](2) () in reasonable isolated yield. Similar reaction of complex with ZnEt(2) also afforded complex ; whereas the reaction of complex with 1 equiv. of n-BuLi in THF afforded the heterodimetallic complex [(THF)Yb(MBMP)(2)Li(THF)(2)] (). All of these complexes were well characterized by elemental analyses, IR spectra, and single-crystal structure determination, in the cases of complexes , and -.     

Insight into the Behaviour of a Lithium Enolate in Solution

(2S,4S)-2-(tert-Butyl)-5-oxo-1,3-dioxolan-4-acetic acid ( 1 ) was dilithiated to the enolate 2 in toluene and THF with lithium diisopropylamide (LiN(i-Pr)₂) under various conditions. Deuteration experiments with 2 showed that two different stable forms of the enolate could be produced, depending on whether the deprotonation of 1 had been carried out in toluene or THF. The generated (i-Pr)₂NH was coordinated to the enolate and, hence, served as a strong lipophilic solvating agent. LiN(i-Pr)₂ could substitute the amine ligands of the two species to a different extent. THF was partially able to displace (i-Pr)₂NH that solvated the species produced in toluene, but the coordination of the amine to the one produced in THF was quantitive. Correlations with given explanations are made.     

Synthesis and structure of diamido ether uranium(IV) and thorium(IV) halide "ate" complexes and their conversion to salt-free bis(alkyl) complexes

The high-yield synthesis, spectroscopic and structural determination of three new uranium(IV) and thorium(IV)ate complexes supported by three different diamido ether ligands are reported. The reaction of Li2[2,6-iPr2PhN(CH2CH2)]2O (Li2[DIPPNCOCN]) with 1 equiv. of UCl4 in THF generates [DIPPNCOCN]UCl3Li(THF)2(1), while reaction in toluene/ether gives salt-free [DIPPNCOCN]UCl2.1/2C7H8(2), which was identified by paramagnetically shifted 1H NMR. Reaction of 0.5 equiv. of {[tBuNON]UCl2}2([tBuNON]=[(CH3)3CN(Si(CH3)2)]2O2-) with 3.5 equiv. LiI in toluene and a minimal amount of THF results in [tBuNON]UI3Li(THF)2(3) and is very similar in structure to 1. {[MesNON]ThCl3Li(THF)}2(4), a dimeric complex with a Th2Li2Cl6 core, is prepared by reaction of Li2[2,4,6-Me3PhN(Si(CH3)2)]2O (Li2[MesNON]) with ThCl4 in THF. The analogous reaction in toluene did not yield the salt-free complex but rather a sterically crowded diligated compound, [MesNON]2Th (5), which was also structurally characterized. Complex 5 was prepared rationally by reacting 2 equiv. Li2[MesNON] with ThCl4 in toluene. The reaction of 1 and 3 with 2 equiv. of LiCH2Si(CH3)3 generates the stable, salt-free organoactinides [DIPPNCOCN]U(CH2Si(CH3)3)2(6) and [tBuNON]U(CH2Si(CH3)3)2(7). Complex 6 was structurally characterized. These reactions illustrate the viability of ate complexes as useful synthetic precursors.     

Investigation of oligomethylmethacrylate-lithium and its donor-acceptor complexes with organometal compounds by means of infrared spectroscopy

Anionic polymerization of methyl methacrylate in THF and toluene at ?70° was studied by means of i.r. spectroscopy. The reaction mixtures show characteristic absorption at 1600–1750 cm^?1 caused by the stretching vibrations of the propagating centre as well as by the groups obtained in side reactions (metal splitting, addition to a carbonyl group, cyclization). Sec-butyllithium is more effective in THF than n-butyllithium, ethyllithium and fluorenyllithium. When polymerizing in toluene, small amounts of a donor (THF or HMPT) cause formation of active centres similar to those in pure THF. The “living” ends of oligo-MMA form 1:1 complexes with electron acceptors such as trialkylaluminium and triethylboron.     

Synthesis of Polymers by Using Fluorene. VI. Free-Radical and Anionic Polymerizations of 9-Fluorenyl and 9-Phenyl-9-fluorenyl Methacrylates

9-Fluorenyl (FMA) and 9-phenyl-9-fluorenyl methacrylates (PFMA) were prepared from methacryloyl chloride with 9-fluorenol and from silver methacrylate with 9-phenyl-9-fluorenyl chloride, respectively. The polymerizations of FMA and PFMA were studied by using α,α′-azobisisobutyronitrile (AIBN), n-butyllithium (n-BuLi), and n-BuLi-(?)-sparteine (Sp) complex in toluene and tetrahydrofuran (THF). Only PFMA polymers obtained with the n-BuLi-Sp complex showed a specific rotation ([α]_D ²¹ ?3 to ?16° in THF).

The number-average molecular weights of the FMA and PFMA polymers were 7 700-16 900 and 1 400-4 700, respectively.     

Intermolecular association of polymers through functional end-groups: Sulphate and sulphonate end-groups

Intermolecular association of some polystyrene and poly(methyl methacrylate) (PMMA) samples bearing sulphate and/or sulphonate end-groups prepared by using the redox initiator systems K₂S₂O₈ + NaHSO₃, Na₂SO₃ + Cu²⁺, NaHSO₃ + O₂ has been studied for dilute solutions in toluene, chloroform, o-dichlorobenzene, tetrahydrofuran (THF) and ethyl acetate respectively by viscometry and in toluene and THF by osmometry. Significant association of the polymers occurs in toluene, chloroform and o-dichlorobenzene in the dilute solutions used in this work. However, association is significantly reduced in chloroform containing 2% ethanol or in toluene containing 2% methanol. Tetrahydrofuran appears to be the preferred solvent for determining the molecular weights of such polymers, since association is insignificant in this solvent.