- Synthesis and molecular structure of the cationic samarium phenoxide complex [(ArO)2Sm(DME)2][BPh4] · THF and its catalytic activity for the polymerization of ε-caprolactone
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The first cationic samarium phenoxide complex, [(ArO)2Sm(DME)2][BPh4] · THF (ArO = 2,6-di-tert-butyl-4-metyl-phenoxide) (1), has been synthesized by one-electron oxidation reaction of (ArO)2Sm(THF)3 with AgBPh4 in high yield and structurally characterized. The complex 1 can be used as a single-component catalyst for the ring-opening polymerization of ε-caprolactone (ε-CL) with high activity. The activity of the complex 1 is much higher than that of the parent neutral complex (ArO)3Sm(THF)2, and is comparable to that of the divalent complex (ArO)2Sm(THF)3. A coordination-insertion polymerization mechanism was supposed according to the end-group analysis.
- Sheng, Hong-Ting,Zhou, Hui,Guo, Hua-Dong,Sun, Hong-Mei,Yao, Ying-Ming,Wang, Jun-Feng,Zhang, Yong,Shen, Qi
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- Reactions of the organoplatinum complex [Pt(cod) (neoSi)Cl] (neoSi = trimethylsilylmethyl) with the non-coordinating anions SbF6- and BPh4
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Reactions of the organoplatinum complex [Pt(cod)(neoSi)Cl] (neoSi = (trimethylsilylmethyl) with the Ag(I) salts of oxo or fluoride containing anions A- = NO3-, ClO4-, OTf - (trifluoromethan
- Neugebauer, Michael,Schmitz, Simon,Krause, Maren,Doltsinis, Nikos L.,Klein, Axel
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- Hydrogenation of cationic dicyclopentadienyl zirconium (IV) alkyl complexes. Characterization of cationic zirconium(IV) hydrides
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The cationic Zr(IV) alkyl complex [Cp2Zr(CH3)(THF)][BPh4] (1) undergoes hydrogenation to the insoluble hydride complex [Cp2Zr(H)(THF)][BPh4] (6) under mild conditions (23°C, 1 atm of H2). This reaction is faster in CH2Cl2 (t1/2 = 5 h) than in THF (t1/2 = 21 h) and in the latter solvent is ca. 5 times faster than hydrogenation of Cp2Zr(CH3)2 (2) to [Cp2Zr(CH3)(μ-H)]2 (8). In CH3CN, 1 forms the 18-electron complex [Cp2Zr(CH3)(CH3CN)2][BPh 4] (3) which does not undergo significant reaction with H2. Reaction of 1 with PMe3 yields [Cp2Zr(CH3)(PMe3)2][BPh4] (10) which undergoes rapid PMe3 exchange at 23°C in THF and CH2Cl2 and very rapid (t1/2 2Zr(H)-(PMe3)2][BPh4] (13). Complex 13 crystallizes in the monoclinic space group P21/c with a = 11.249 (4) A?, b = 19.082 (6) A?, c = 17.391 (5) A?, β = 99.57 (3)°, Z = 4, and RwF = 6.53%. 13 exhibits a normal bent metallocene structure with the hydride ligand in the central position in the plane between the two Cp- ligands. PMe2Ph coordinates weakly to 1; in the presence of 17 equiv of PMe2Ph, 1 undergoes rapid (t1/2 = ca. 8 min) hydrogenation to the nonlabile hydride complex [Cp2Zr(H)(PMe2Ph)2][BPh4] (15) which by NMR is isostructural with 13. Neither PMePh2 nor PPh3 react with 1 to form detectable phosphine complexes. The presence of 17 equiv of PMePh2 produces a minor acceleration of the hydrogenation of 1 (t1/2 = 5 h, THF) and results in the formation of [Cp2Zr(H)(PMePh2)2][BPh4] (16) which by NMR is isostructural with 13 and 15. PPh3 does not accelerate the hydrogenation of 1 and does not produce a phosphine hydride product. The 18-electron complex [Cp2Zr(CH3)(dmpe)][BPh4] (11) does not react with H2 even at elevated temperatures. As for neutral Cp2Zr(R)(X) complexes, the hydrogenation reactivity of Cp2Zr(CH3)+ complexes depends strongly upon the availability of a low-energy Zr LUMO for interaction with H2. The acceleration of the hydrogenation of 1 by PMe3 and PMe2Ph is ascribed to the removal of Zr-O π-bonding upon substitution of THF by phosphine.
- Jordan, Richard F.,Bajgur, Chandrasekhar S.,Dasher, William E.,Rheingold, Arnold L.
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- Cerium(III) and cerium(IV) bis(η8-pentalene) sandwich complexes: Synthetic, structural, spectroscopic, and theoretical studies
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The Ce(III) anionic bis(pentalene) sandwich complex K[Ce{C 8H4(SiiPr3-1,4)2} 2] (1) has been prepared by treatment of CeCl3 with K 2[C8H4(SiiPr3-1,4) 2] and crystallographically characterized as its 18-crown-6 complex. Oxidation of 1 with Ag[BPh4] affords the neutral, formally Ce(IV) sandwich complex [Ce{C8H4(SiiPr 3-1,4)2)2] (2), whose molecular structure has also been determined. The electronic structure of 2 has been investigated in detail by a combination of magnetic studies, K-edge XANES measurements, gas-phase photoelectron spectroscopy, and density functional calculations.
- Balazs, Gabor,Geoffrey N Cloke,Green, Jennifer C.,Harker, Robert M.,Harrison, Andrew,Hitchcock, Peter B.,Jardine, Christian N.,Walton, Richard
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- Self-Assembly of Stimuli-Responsive [2]Rotaxanes by Amidinium Exchange
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Advances in supramolecular chemistry are often underpinned by the development of fundamental building blocks and methods enabling their interconversion. In this work, we report the use of an underexplored dynamic covalent reaction for the synthesis of stimuli-responsive [2]rotaxanes. The formamidinium moiety lies at the heart of these mechanically interlocked architectures, because it enables both dynamic covalent exchange and the binding of simple crown ethers. We demonstrated that the rotaxane self-assembly follows a unique reaction pathway and that the complex interplay between crown ether and thread can be controlled in a transient fashion by addition of base and fuel acid. Dynamic combinatorial libraries, when exposed to diverse nucleophiles, revealed a profound stabilizing effect of the mechanical bond as well as intriguing reactivity differences between seemingly similar [2]rotaxanes.
- Borodin, Oleg,Richter, Stefan,Robertson, Craig C.,Shchukin, Yevhenii,Von Delius, Max
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supporting information
p. 16448 - 16457
(2021/10/12)
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- Uranium(III) complexes supported by hydrobis(mercaptoimidazolyl)borates: synthesis and oxidation chemistry
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The reaction of [UI3(thf)4] with the sodium or lithium salts of hydrobis(2-mercapto-1-methylimidazolyl)borate ligands ([H(R)B(timMe)2]?) in a 1?:?2 ratio, in tetrahydrofuran, gave the U(iii) complexes [UI{κ3-H,S,S′-H(R)B(timMe)2}2(thf)2] (R = H (1), Ph (2)) in good yields. Crystals of [UI{κ3-H,S,S′-H(Ph)B(timMe)2}2(thf)2] (2) were obtained by recrystallization from a tetrahydrofuran/acetonitrile solution, and the ion-separated uranium complex [U{κ3-H,S,S′-H(Ph)B(timMe)2}2(CH3CN)3][I] (3-I) was obtained by dissolution of 2 in acetonitrile followed by recrystallization. One-electron oxidation of 2 with AgBPh4 or I2 resulted in the formation of the cationic U(iv) complexes [U{κ3-H,S,S′-H(Ph)B(timMe)2}3][X] (X = BPh4 (6-BPh4), I (6-I)), due to a ligand redistribution process. These complexes are the first examples of homoleptic poly(azolyl)borate U(iv) complexes. Treatment of complex 2 with azobenzene led to the isolation of crystals of the U(iv) compound [UI{κ3-H(Ph)B(timMe)2}2(κ2-timMe)] (7). Treatment of 2 with pyridine-N oxide (pyNO) led to the formation of the uranyl complex [UO2{κ2-S,S′-H(Ph)B(timMe)2}2] (8) and of complex 6-I, while from the reaction of [U{κ3-H(Ph)B(timMe)2}2(thf)3][BPh4] (5) with pyNO, the oxo-bridged U(iv) complex [{U{κ3-H(Ph)B(timMe)2}2(pyNO)}2(μ-O)][BPh4]2 (9) was also obtained. In the U(iii) and U(iv) complexes, the bis(azolyl)borate ligands bind to the uranium center in a κ3-H,S,S′ coordination mode, while in the U(vi) complex the ligands bind to the metal in a κ2-S,S′ mode. The presence of U...H-B interactions in the solid-state, for the nine-coordinate complexes 1, 2, 3, 6 and 7 and for the eight-coordinate complex 9, was supported by IR spectroscopy and/or X-ray diffraction analysis.
- Maria, Leonor,Santos, Isabel C.,Santos, Isabel
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p. 10601 - 10612
(2018/08/17)
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- Regioselective hydroamination of acrylonitrile catalyzed by cationic pincer complexes of nickel(II)
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The cationic pincer-type complexes [{((i-Pr2PCH 2CH2)2CH}Ni(NCCH3)][BPh 4] (1), [{2,6-(i-Pr2PCH2)2-C 6H3}Ni(NCCH3)][BPh4] (2), [{2,6-(i-Pr2PO)2-C6H3}Ni(NCCH 3)][BPh4] (3), and [{2,6-(i-Pr2PO) 2-3,5-Cl2-C6H}Ni(NCCH3)][BPh 4] (6) have been prepared and fully characterized by NMR spectroscopy and X-ray crystallography. Cyclic voltammetry measurements of the Ni - Br precursors of 2, 3, and 6 indicated that substituting the CH2 moiety in the ligand skeleton by O, or some of the aromatic protons by Cl, renders the metal center less susceptible to oxidation. Evaluating the catalytic activities of 1-3, 6, and the t-Bu analogue of 1 for addition of aniline to acrylonitrile showed 3 to be the most competent catalyst precursor. Isolation of [{(t-Bu 2PCH2CH2)2CH)Ni(NCCH 2CH2NHPh)][BPh4] (7) from the reaction of [{(t-Bu2PCH2CH2)2CH}Ni(NCCH=CH 2)][BPh4] with aniline suggests that these cationic precursors act as Lewis acids that bind the nitrile moiety of acrylonitrile, thereby activating the olefinic moiety toward nucleophilic attack by aniline.
- Castonguay, Annie,Spasyuk, Denis M.,Madern, Nathalie,Beauchamp, Andre L.,Zargarian, Davit
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p. 2134 - 2141
(2009/08/14)
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- Identification of [M(II)(arene)2]2+ (M = V, Cr) as the key intermediate in the formation of V[TCNE](x)(·)ySolvent magnets and Cr[TCNE](x) (·) Solvent
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To elucidate the mechanism of the reaction between V0(C6H6)2 and tetracyanoethylene (TCNE) that leads to the room-temperature magnet V[TCNE]](x)(·)yCH2Cl2 (x ~2; y ~ 1/2 ), reactions between bis(arene)- vanadium (arene = 1,3,5-trimethylbenzene, 1,3,5-tri-tert-butylbenzene) and its cations and TCNE and its anion were studied. The reaction of V°(arene)2 with TCNE yields magnets with critical temperatures ranging from 28 to 400 K. Products from the reaction of [V(I)(arene)2]+ with [TCNE](·)-) were not magnets; however, reaction of [V(I)(arene)2]+ with [TCNE](·)-) in the presence of TCNE forms a magnetically ordered material. The reaction of V0(1,3,5-C6H3Me3)2 with 2 equiv of one-electron oxidant [Fe(III)(C5H5)2]+, and subsequently with [TCNE](·)-, also leads to a magnetic material. The results of these investigations suggest that V0(arene)2 undergoes two one-electron oxidation reactions with TCNE to form sequentially [V(I)(arene)2]+ and '[V(II)(arene)2]2+', the latter being the key intermediate that reacts with [TCNE](·) - to produce the magnetic product. [V(I)(arene)2]+ has been isolated, whereas and '[V(II)(arene)2]2+' has not. The one-electron oxidation of V0[C6H3(t- Bu)3]2 with Ag-[BPh4] produces {V(I)[C6H3(t-Bu)3]2}+[BPh4]-. The stoichiometric reaction of V0[C6H3(t-Bu)3]2 with TCNE leads to paramagnetic {V(I)[1,3,5-C6H3(tBu)3]2}+[TCNE](·) -. {V(I)[C6H3(t- Bu)3]2}+[BPh4]- and {V(I)[1,3,5-C6H3-(tBu)3]2}+[TCNE](·) - have been structurally characterized. When [V(II)(NCMe)6]{B[3,5- C6H3(CF3)2]4}2 is reacted with [TCNE](·) -, a route that does not use bis(arene)vanadium complexes, a magnetic precipitate is also produced. As established earlier, the reaction of Cr0(arene)2 with TCNE forms nonmagnetically ordered [Cr(I)(arene)2](·)+-[TCNE](·) -. Reaction of lower oxidation potential Cr0Np2 (Np = naphthalene) with TCNE putatively forms '[Cr(II)Np2]2+' which reacts with [TCNE](·)- to form Cr[TCNE](x)·yS, which was isolated and, unexpectedly, does not magnetically order. Similar results are obtained when [Cr(II)(NCMe)4][BF4]2 or [Cr(II)(NCMe)6][B(3,5-C6H3(CF3)2)4]2 is reacted with [n-Bu4N][TCNE].
- Gordon, Douglas C.,Deakin, Laura,Arif, Atta M.,Miller, Joel S.
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p. 290 - 299
(2007/10/03)
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- 1,4,7,10-Tetraazatetracyclo[5.5.1.04,13.010,13 ]tridecane and its conjugate acids
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1,4,7,10-Tetraazatetracyclo[5.5.1.04,13.010,13 ]tridecane -tridecane which can reversibly and successively add two moles of acids to form conjugate acids, can be made by condensation of 1,4,7,10-tetraazacyclododecane with ethyl orthocarbonate or by the condensation of 2,3,5,6-tetrahydro-1H-imidazo[1,2-a]imidazole with ethyl bis(2-chloroethyl)carbamate followed by acid hydrolysis. The salts with acids having photographically innocuous anions can be used in developers for silver halide emulsion to reduce fog, and can be used in the emulsions themselves as sensitizers.
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