Removal Of THF Research Articles

Flash precipitation of random copolymers in a micro-mixer for controlling the size and surface charge of nanoparticles.

Precisely controlling the size and surface chemistry of polymeric nanoparticles (P-NPs) is critical for their versatile engineering and biomedical applications. In this work, various NPs of amphipathic random copolymers were comparatively produced by the flash nanoprecipitation (FNP) method using a tube-in-tube type of micro-mixer up to 330 mg min-1 in production scale in a kinetically controlled manner. The NPs obtained from poly(styrene-co-maleic acid), poly(styrene-co-allyl alcohol), and poly(methyl methacrylate-co-methacrylic acid) were concurrently controlled in the range 51-819 nm in size with narrow polydispersity index (<0.1) and -44 to -16 mV in zeta potential, by depending not only on the polymeric chemistry and the concentration but also the mixing behavior of good solvents (THF, alcohols) and anti-solvent (water) under three flow regimes (laminar, vortex and turbulence, turbulent jet). Moreover, the P(St-MA) derived NPs under turbulent jet flow conditions were post-treated in the initial solution mixture for up to 16 h, resulting in lowering of the zeta potential to -52 mV from the initial -27 mV and decreasing size to 46 nm from 50 nm by further migration of hydrophilic segments with -COOH groups on the outer surface, and the removal of THF trapped in the hydrophobic core.

Structural Diversity and Multielectron Reduction Reactivity of Samarium(II) Iodido-β-diketiminate Complexes Dependent on Tetrahydrofuran Content.

The molecular structures of complexes [Sm(Nacnac)I(thf)n] (Nacnac = HC(C(Me)Ndipp)2-, dipp = 2,6-diisopropylphenyl, thf = tetrahydrofuran) depending on the number of thf ligands are studied. The complete removal of thf from a known complex [Sm(Nacnac)I(thf)2] leads to a tetranuclear product [Sm(Nacnac)I]4 (4). The partial removal of thf results in mixtures of dinuclear [Sm2(Nacnac)2I2(thf)] (2), trinuclear [Sm3(Nacnac)3I3(thf)] (3), and tetranuclear [Sm4(Nacnac)4I4(thf)2] (4*) complexes and 4, depending on the conditions. The reaction of solvent-free SmI2 with 1 equiv of K(Nacnac) results mainly in [Sm(Nacnac)2] (1), while the interaction of 4 with certain amounts of thf allows obtaining pure 2 and 3 (with the admixture of 4*). Complex 4* is the exact dimer of 2, and both compounds are stable in solutions. Reactions with 3 and 4 as reductants are studied. 4 is oxidized by I2 to stoichiometrically yield two products, mixed-valent tetranuclear [Sm4(Nacnac)4I5] (5) and binuclear [Sm(Nacnac)I2]2 (6) complexes. In the reaction of 4 with nBu3PTe, a trinuclear complex [Sm3(Nacnac)3(μ-I)3(μ3-E)2] (8, E = I or Te) is formed in small amounts, with the formation of 6 as the second product. 3 serves as a two-electron reductant in the reaction with nBu3PTe to yield a trinuclear complex [Sm3(Nacnac)3I3(μ-Te2)] (7). Complexes 2, 4, 4*, 5, 6, and 8 possess a unique flat SmxIy core of heavy atoms, which is assumed to be a consequence of the Nacnac ligand geometry.

Isolation of an Elusive Phosphametallacyclobutadiene and Its Role in Reversible Carbon−Carbon Bond Cleavage

AbstractThe reactivity of phosphaalkynes, the isolobal and isoelectronic congeners to alkynes, with metal alkylidyne complexes is explored in this work. Treating the tungsten alkylidyne [tBuOCO]W≡CtBu(THF)2 (1) with phosphaalkyne (10) results in the formation of [O2C(tBuC=)W{η2‐(P,C)−P≡C−Ad}(THF)] (13‐tBuTHF) and [O2C(AdC=)W{η2‐(P,C)−P≡C−tBu}(THF)] (13‐AdTHF); derived from the formal reductive migratory insertion of the alkylidyne moiety into a W−Carene bond. Analogous to alkyne metathesis, a stable phosphametallacyclobutadiene complex [tBuOCO]W[κ2‐C(tBu)PC(Ad)] (14) forms upon loss of THF from the coordination sphere of either 13‐tBuTHF or 13‐AdTHF. Remarkably, the C−C bonds reversibly form/cleave with the addition or removal of THF from the coordination sphere of the formal tungsten(VI) metal center, permitting unprecedented control over the transformation of a tetraanionic pincer to a trianionic pincer and back. Computational analysis offers thermodynamic and electronic reasoning for the reversible equilibrium between 13‐tBu/AdTHF and 14.

Isolation of an Elusive Phosphametallacyclobutadiene and Its Role in Reversible Carbon-Carbon Bond Cleavage.

The reactivity of phosphaalkynes, the isolobal and isoelectronic congeners to alkynes, with metal alkylidyne complexes is explored in this work. Treating the tungsten alkylidyne [t BuOCO]W≡Ct Bu(THF)2 (1) with phosphaalkyne (10) results in the formation of [O2 C(t BuC=)W{η2 -(P,C)-P≡C-Ad}(THF)] (13-t BuTHF ) and [O2 C(AdC=)W{η2 -(P,C)-P≡C-t Bu}(THF)] (13-AdTHF ); derived from the formal reductive migratory insertion of the alkylidyne moiety into a W-Carene bond. Analogous to alkyne metathesis, a stable phosphametallacyclobutadiene complex [t BuOCO]W[κ2 -C(t Bu)PC(Ad)] (14) forms upon loss of THF from the coordination sphere of either 13-t BuTHF or 13-AdTHF . Remarkably, the C-C bonds reversibly form/cleave with the addition or removal of THF from the coordination sphere of the formal tungsten(VI) metal center, permitting unprecedented control over the transformation of a tetraanionic pincer to a trianionic pincer and back. Computational analysis offers thermodynamic and electronic reasoning for the reversible equilibrium between 13-t Bu/AdTHF and 14.

From Stereochemically Tunable Homopolymers to Stereomultiblock Copolymers: Lewis Base Regulates Stereochemistry in the Coordination Polymerization of 2-Vinylpyridine

Excellent isoselectivity (mmmm > 99%) and high activity (TOF > 4000 h–1) were achieved for the first time in the polymerization of the polar 2-vinylpyridine by using the simple lutetium-based catalysts, Lu(CH2SiMe3)3(THF)x(Py)2–x (x = 0, 1, 2). The isoselectivity (mm) of the polymer could be varied between 37% and 99% through simply altering the quantity of Lewis base (tetrahydrofuran, 1,4-diazabicyclo[2.2.2]octane, 3-bromopyridine, and pyridine) added. Moreover, a novel method for preparing isotactic–atactic stereomultiblock poly(2-vinylpyridine)s was developed by the addition and removal of THF during polymerization. The polymerization process including stereoselective control mechanism was deduced by DFT calculations.

Improved Procedure for Single-electron-transfer-induced Grignard Cross-coupling Reaction

Abstract Aryl Grignard reagents were found to undergo coupling with aryl or alkenyl bromides in the presence of LiCl in a mixed solvent consisting of toluene and THF (2/1). Previously employed removal of THF with evacuation from Grignard solutions is no longer needed to obtain biaryls and styrene derivatives.

ChemInform Abstract: Synthesis and Single Crystal Structure of Sodium Octahydrotriborate, NaB3H8.

AbstractThe title compound is prepared by a modified synthesis involving the reduction of BH3·THF with Na dispersed on silica gel (‐10 °C), removal of THF, and extraction by Et2O.

Dinitrogen binding at vanadium in a tris(alkoxide) ligand environment

We report the first tris(alkoxide)V(III) complex to bind dinitrogen. Removal of THF from V(OR)(3)THF furnishes the highly reactive V(OR)(3) fragment, which binds dinitrogen to form [V(OR)(3)](2)(μ-N(2)) in the solid state. Dinitrogen is readily released upon dissolution of the complex. Structural and DFT studies are consistent with significant activation of N(2) when bound by the vanadium tris(alkoxide) platform.

A comparative study of pi-arene-bridged lanthanum arylamide and aryloxide dimers. Solution behavior, exchange mechanisms, and X-ray crystal structures of La2(NH-2,6-iPr2C6H3)6, La(NH-2,6-iPr2C6H3)3(THF)3, and La(NH-2,6-iPr2C6H3)3(py)2.

Reaction of 3 equiv of 2,6-diisopropylaniline with La[N(SiMe(3))(2)](3) produces the dimeric species La(2)(NHAr)(6) (1). X-ray crystallography reveals a centrosymmetric structure, where the dimeric unit is bridged by intermolecular eta(6)-arene interactions of a unique arylamide ligand attached to an adjacent metal center. Exposure of 1 to THF results in formation of the monomeric tris-THF adduct La(NHAr)(3)(THF)(3) (2), which was shown by X-ray crystallography to maintain a fac-octahedral structure in the solid state. (1)H NMR spectroscopy illustrates that the binding of THF to 1 to form 2 is reversible and removal of THF under vacuum regenerates dimeric 1. Addition of pyridine to 1 yields the monomeric bis-pyridine adduct La(NHAr)(3)(py)(2) (3), which exhibits a distorted trigonal-bipyramidal La metal center. Solution (1)H NMR, IR, and Raman spectroscopy indicate that the pi-arene-bridged dimeric structure of 1 is maintained in solution. Variable-temperature (1)H NMR spectroscopic investigations of 1 are consistent with a monomer-dimer equilibrium at elevated temperature. In contrast, variable-temperature (1)H NMR spectroscopic investigations of the aryloxide analogue La(2)(OAr)(6) (4) show that the bridging and terminal aryloxide groups exchange by a mechanism in which the dimeric nature of the compound is retained. Density functional theory (DFT) calculations were carried out on model compounds La(2)(OC(6)H(5))(6), La(2)(NHC(6)H(5))(6), and (C(6)H(5)R)La(XC(6)H(5))(3), where X = O or NH and R = H, OH, or NH(2). The formation of eta(6)-arene interactions is energetically favored over monomeric LaX(3) (X = OPh or NHPh) with the aryloxide pi-arene interaction being stronger than the arylamide pi-arene interaction. Calculation of vibrational frequencies reveals the origin of the observed IR spectral behavior of both La(2)(OC(6)H(5))(6) and La(2)(NHC(6)H(5))(6), with the higher energy nu(C=C) stretch due to terminal ligands and the lower energy stretch associated with the bridging ligands.

Synthesis and characterisation of magnesium methyl complexes with monoanionic chelating nitrogen donor ligands and their reaction with dioxygen

Treatment of the Grignard reagent MeMgCl with the lithiates Li[L–X] (Li[L–X] = lithium β-diketiminate [HC{C(Me)NAr′}2Li] (Ar′ = 2,6-diisopropylphenyl) or lithium N,N′-diisopropylaminotroponiminate, Li[(iPr2)ATI]) in THF provided four-co-ordinate methylmagnesium complexes [Mg(η2-L–X)Me(THF)]. The β-diketiminate complex has been characterised by X-ray crystallography, however the aminotroponiminate complex is an oil. Both complexes readily react with oxygen to provide methoxide-bridged dimeric complexes [Mg(μ-OMe)(η2-L–X)]2 and the complex [Mg(μ-OMe){η2-(iPr2)ATI}]2 has structurally been characterised. The methyl-bridged dimeric complex [Mg(μ-Me){HC[C(Me)NAr′]}2]2 may be obtained by removal of THF from the adduct under vacuum at 150 °C or by treatment of the β-diketimine (L–XH) with dimethylmagnesium in toluene with elimination of methane, and has also been characterised crystallographically. In contrast to this, treatment of MgMe2 with the aminotriponimine H[(iPr2)ATI] provides only the bis-chelate complex [Mg{(iPr2)ATI}2] which has also been characterised structurally. However the methyl bridged dimer [Mg(μ-Me){η2-(iPr2)ATI}]2 may be formed by removal of THF from [MgMe{η2-(iPr2)ATI}(THF)] at 110 °C under vacuum.

Ethylenebis(salicylideneiminato)zirconium Dichloride: Crystal Structure and Use as a Heterogeneous Catalyst in the Polymerization of Ethylene

In the solid-state structure of the Schiff base salen [salen = N,N‘-ethylenebis(salicylideneiminato)] zirconium dichloride complex Zr(salen)Cl2(THF), C20H22Cl2N2O3Zr, a quadridentate ligand, occupies four sites in the pseudopentagonal bipyramidal coordination. The coordination sphere is completed by one THF molecule, and two chloride ions are forced into the trans-position. Removal of THF, while Zr(salen)Cl2(THF) is heated in toluene, leads to a six-coordinated complex with the two chloride ligands assuming the cis-position. This property was successfully utilized in the preparation of a homogeneous Zr(salen)Cl2 catalyst precursor. Heating of Zr(salen)Cl2(THF) in toluene in the presence of SiO2 causes deposition of Zr(salen)Cl2 on to the silica support, producing a heterogeneous catalyst, which shows an acceptable activity in ethylene polymerization at 80 °C and at low ethylene pressures in the presence of the cocatalyst methylaluminoxane.

The role of ligand steric hindrance in determining the stability of very short VV contacts. Preparation and characterization of a series of V (II) and V (III) amidinates

The reaction of VCl2 (TMEDA)2 and of VCl3(THF)3 with two equivalents of formamidinate lithium salts, respectively, yielded dimeric ∗[CyNC(H) NCy]2V∗2 (2), with a very short VV multiple bond and ∗[CyNC(H)NCy]∗2 (4) which is also dimeric. The formation of 2 proceeded through the intermediate monomeric [CyNC (H) NCy]2 V(TMEDA) (1) which was isolated and fully characterized. The dinuclear structure was reversibly cleaved by treatment with pyridine forming the monomeric [CyNC(H)NCy]2V(Py)2 (3). Conversely, similar reactions with acetamidinate anion gave only the monomeric [CyNC(Me)NCy]2 V (THF)2 (5a) and [CyNC(Me)NCy]2VCl (7), respectively. Attempts to form a dinuclear structure by either removal of THF from 5a or reduction of 7 gave only the V (III) compound [CyNC(Me)NCy]3V (6). In the case of the very bulky benzamidinate ligand, similar monomeric complexes [Me3SiNC (Ph) NSiMe3]2 V (THF)2 (5c) and [Me3SiNC(Ph) NSiMe3]2 VCl (10) were obtained. However, attempts to form dinuclear species via THF dissociation from 5c or reduction of 10 gave a novel dinitrogen complex ∗[Me3SiNC(Ph)NSiMe3]2V∗2 (8). Crystal data are as follows. 1: C32H62N6V, monoclinic, P21/a, a = 18.085 (3), b = 10.737 (2), c = 18.721 (2) Å, β = 114.37 (4) °, Z = 4; 2: C52H92N8V2, monoclinic, P21, a = 11.671 (3), b = 10.371 (2), c = 22.645 (3) Å, β = 100.65 (1)°, Z = 2; 5c: C34H62N4Si4O2V, orthorhombic, Pbcn, a = 18.133 (7), b = 12.504 (6), c = 17.428 (4) Å, Z = 4; 6: C42H75N6V, monclinic P21/c, c = 22.777 (4) Å,β = 103.04 (2)°, Z = 4; 7: C28H50N4VCl, triclinic, P-1, a = 11.132 (4), b = 13.630 (4), c = 10.276 (2) Åα= 95.92 (2), β = 98.38 (2), γ = 109.29 (3)°, Z = 2; 8: C52H92N10V2Si8, triclinic, P-1, a = 14.181 (2), b = 18.713 (2), c = 13.257 (2) Å, α = 99.48 (1), β = 94.13(2), γ = 91.87 (2)°, Z = 2; 10: C26H46N4VClSi4, triclinic, P-1, a = 12.781 (5), b = 13.128 (4), c = 12.126 (5) Å, α =104.85 (3), β =113.29 (4), γ = 66.80 (4)°, Z = 2.

Darstellung und Eigenschaften von und Reaktionen mit metallhaltigen Heterocyclen, LII. Bindungs- und Strukturverhältnisse von Phosphidocobaltaten in Lösung und im festen Zustand/ Preparation and Properties of, and Reactions with, Metal-Containing Heterocycles, LII. Bonding and Structural Conditions of Phosphidocobaltates in Solution and in Solid State

Abstract Reduction of [(OC)3CoPPh2]n (1a ) with excess sodium granules affords [(OC)3CoPPh2]Na2 (3a) in solution as well as in solid state. However, in analogous reactions of [(OC)3CoPR2H]2 (1b : R = C6H11; 1c : R = t-Bu) with excess sodium granules the monovalent anionic complexes [(OC)3CoPR2H]Na (2b, c) are obtained in THF solution. 2b, c cannot be isolated in solid state. After removal of THF from their solutions the purified residues were identified by elemental analyses as [(OC)3CoPR2]Na2 (3b, c). Addition of buthyllithium to THF solutions of 3a, 2b, c gives rise to differently solvated complexes 3a*-c* which are transformed to [(OC)3CoPR2]M2 (M = N a, Li; 3 a′-c′). The course of the reactions and the products are controlled IR and 31PNMR spectroscopically. 2b, c and 3a, b′, c′ were trapped with (H3CO)2SO2 and CH2X2(X = Cl, I) yielding H3CCo(CO)3PR2H(6b, c), H3CCo(CO)3PR2CH3 (4a - c ) and [xxx] (5a, b), respectively.

Lanthanide carbonyl complexes

In the cases of a typical lanthanide (Sm) and atypical lanthanide (Yb), they have shown that activated metallic Sm and Yb react with free CO (p/sub CO/ = 20 atm) at 20/sup 0/C in THF to give carbonyl complexes Ln(CO)/sub m/(THF)/sub n/ (Ln = Sm and Yb) (I). Two bands (1995 and 2020 cm/sup -1/) are found in the IR spectra of solutions of (I) in THF in the stretching band region for the terminal CO ligands. The position and relative intensity of these bands is virtually independent of the nature of the lanthanide (in contrast to the data obtained in a matrix (2)). Complexes (1) are stable in THF for several hours. An attempt to isolate (I) from solution by removal of THF leads to decomposition of the complex and formation of a lanthanide-containing powder insoluble in organic solvents having apparent polymeric structure. The presence of lanthanide was shown by x-ray fluorescence analysis. The IR spectra of these compounds have bands at 1747 and 1754 cm/sup -1/ which may be assigned to stretching vibrations of the bridge CO groups.

Tetrahydrocortisol metabolism in man

Tetrahydrocortisol (THF) metabolism was studied by I.V. administration of trace amounts of 3H-THF to 3 normal men and 4 patients with miscellaneous illnesses. The principal urinary steroid was THF. This constituted about half of the “glucosiduronates” in the normal subjects, but significantly more (61–79%) in 3 of the 4 patients. Reduction of the 20-ketone of THF was quantitatively less prominent than the corresponding reaction for THE, but similarly stereoselective. Total cortols constituted 2–12% of the “glucosiduronates”, and the 111β-epimer predominated by about 15:1. The major conversion product of THF was 11β-hydroxyetiocholanolone, 12–25% of the “glucosiduronates” in normal subjects. Three of the four patients showed significantly diminished formation of this metabolite (3–5% of the “gluco-siduronate”). This suggests that diminished side-chain removal of THF may occur non-specifically in ill subjects. In one of these 3 patients, the low 11β-hydroxy-etiocholanolone formation was associated with extremely high β-cortol formation (32% of the “glucosiduronate” suggesting that β-cortol serves as one of the immediate precursors of 11β-hydroxyetiocholanolone.