- Molybdenum and nickel atrane complexes with a rigid tripodal tetraphosphine ligand incorporating imidazole rings
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Tripodal, tetradentate tetraphosphine ligand tris(1H-2-diisopropylphosphinoimidazol-1-yl)phosphine (1) was synthesized in three straightforward steps from widely available starting materials. The ligand crystallized in a C3-like conformation suitable for metal coordination. Nickel(II) complex 2 was prepared from 1 and Ni(dme)Br2 and adopted a classical atrane structure with trigonal pyramidal geometry at the metal, a bromide covalently bonded in the axial position, and a bromide ion in the outer coordination sphere. Molybdenum(III) complex 3 was prepared from 1 and MoCl3(thf)3 and could be structurally characterized using a co-crystal with Cp2Co and [Cp2Co]Cl. It displayed a face-capped octahedral geometry at the seven-coordinated metal. Complexes 2 and 3 proved prone to decomposition under reductive and oxidative conditions, hindering the investigation of their chemistry. Crystallization attempts from acetonitrile led to the isolation of dinuclear hydrolysis product 4, with the Mo(III) centres bridged by two chlorides and two 2-(diisopropylphosphino)imidazole moieties in a paddlewheel arrangement.
- Gendy, Chris,Spasyuk, Denis,Harrison, Alexander,Roesler, Roland
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- Strong electronic and magnetic coupling in M4(M = Ni, Cu) clusters via direct orbital interactions between low-coordinate metal centers
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We present an extensive study of tetranuclear transition-metal cluster compounds M4(NPtBu3)4 and [M4(NPtBu3)4][B(C6F5)4] (M = Ni, Cu; tBu = tert-butyl), which feature low-coordinate metal centers and direct metal-metal orbital overlap. X-ray diffraction, electrochemical, magnetic, spectroscopic, and computational analysis elucidate the nature of the bonding interactions in these clusters and the impact of these interactions on the electronic and magnetic properties. Direct orbital overlap results in strongly coupled, large-spin ground states in the [Ni4(NPtBu3)4]+/0 clusters and fully delocalized, spin-correlated electrons. Correlated electronic structure calculations confirm the presence of ferromagnetic ground states that arise from direct exchange between magnetic orbitals, and, in the case of the neutral cluster, itinerant electron magnetism similar to that in metallic ferromagnets. The cationic nickel cluster also possesses large magnetic anisotropy exemplified by a large, positive axial zero-field splitting parameter of D = +7.95 or +9.2 cm-1, as determined by magnetometry or electron paramagnetic resonance spectroscopy, respectively. The [Ni4(NPtBu3)4]+ cluster is also the first molecule with easy-plane magnetic anisotropy to exhibit zero-field slow magnetic relaxation, and under a small applied field, it exhibits relaxation exclusively through an Orbach mechanism with a spin relaxation barrier of 16 cm-1. The S = 1/2 complex [Cu4(NPtBu3)4]+ exhibits slow magnetic relaxation via a Raman process on the millisecond time scale, supporting the presence of slow relaxation via an Orbach process in the nickel analogue. Overall, this work highlights the unique electronic and magnetic properties that can be realized in metal clusters featuring direct metal-metal orbital interactions between low-coordinate metal centers.
- Chakarawet, Khetpakorn,Atanasov, Mihail,Marbey, Jonathan,Bunting, Philip C.,Neese, Frank,Hill, Stephen,Long, Jeffrey R.
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- Iron and nickel complexes containing β-diketiminato ligands with thioether tethers
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A novel β-diketiminato ligand precursor, LH (II), containing thioether tethers was synthesized by the reaction of acetylacetone and 2-methylthioaniline. II was deprotonated and used in the synthesis of two iron(II) complexes, [LFeCl] (1), and [LFeOTf] (2)
- Pfirrmann, Stefan,Limberg, Christian,Hoppe, Elke
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- Diastereoselective Synthesis of Aryl C-Glycosides from Glycosyl Esters via C?O Bond Homolysis
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C-aryl glycosyl compounds offer better in vivo stability relative to O- and N-glycoside analogues. C-aryl glycosides are extensively investigated as drug candidates and applied to chemical biology studies. Previously, C-aryl glycosides were derived from lactones, glycals, glycosyl stannanes, and halides, via methods displaying various limitations with respect to the scope, functional-group compatibility, and practicality. Challenges remain in the synthesis of C-aryl nucleosides and 2-deoxysugars from easily accessible carbohydrate precursors. Herein, we report a cross-coupling method to prepare C-aryl and heteroaryl glycosides, including nucleosides and 2-deoxysugars, from glycosyl esters and bromoarenes. Activation of the carbohydrate substrates leverages dihydropyridine (DHP) as an activating group followed by decarboxylation to generate a glycosyl radical via C?O bond homolysis. This strategy represents a new means to activate alcohols as a cross-coupling partner. The convenient preparation of glycosyl esters and their stability exemplifies the potential of this method in medicinal chemistry.
- Wei, Yongliang,Ben-zvi, Benjamin,Diao, Tianning
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supporting information
p. 9433 - 9438
(2021/03/16)
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- Simple and Strong Dative Attachment of α-Diimine Nickel (II) Catalysts on Supports for Ethylene Polymerization with Controlled Morphology
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Abstract: In this article, preparation of novel spherical MgCl2 supported α-diimine nickel (II) catalysts for ethylene polymerization in slurry phase is reported. α-Diimine ligands were synthesized by condensation reaction of 2, 6-disubstituted alkyls or aryls anilines and Ace naphthoquinone Which have hydroxyl functionality in their para-position. Hydroxyl functionalized α-diimine attached strongly on to the spherical MgCl2 support surface by dative bonding. No linker was needed to attach the complexes onto the support surface and the amount of loaded Nickel was controllable to improve morphology and especially bulk density of polymer powder. A significant reduction in catalysts activity has happened when homogeneous catalysts were supported onto silica but this reduction was decreased when they were supported onto thermally treated spherical MgCl2. As homogeneous bis(N,N′-(4-(3-hydroxyl-propyl)-2,6-di[(4-tert-butyl-phenyl)-phenyl) amino] Ace naphthoquinone Nickel dibromide(d) showed the highest activity among other evaluated homogeneous catalysts, its MgCl2 supported catalyst (d/S-MgCl2) has shown the highest activity among MgCl2 supported catalysts too. These MgCl2 supported catalysts were pre-polymerized in presence of ethylene monomer in the mild polymerization condition to yield a pre-polymerized catalyst with polymer/catalyst weight ratio equal to six. Ethylene polymerization was carried out to make spherical particles of polyethylene without reactor fouling by these pre-polymerized catalysts. Clearly, it is shown in SEM images that the spherical morphology of MgCl2 support is replicated in the produced polymer. The molecular weight and molecular weight distribution of produced polymer with MgCl2 supported catalysts were higher than those produced by homogeneous catalysts. Graphic Abstract: α–Diimine nickel (II) complexes have hydroxy functionality where produce strong dative bonding onto spherical MgCl2. This bonding is strong enough that these catalysts are suitable for slurry polymerization of ethylene without reactor fouling due to catalyst leaching from support. The chemical structure of MgCl2 leads to high active supported catalysts. The molecular weight and polydispersity index of produced polymrers using these supported catalysts are higher than those produced by equivalent homogeneous catalysts and are controllable by selection of appropriate ligand for used α–diimine nickel (II) complex or hydrogen concentration in ethylene polymerization.[Figure not available: see fulltext.].
- Kianfar, Ehsan,Azimikia, Reza,Faghih, Seyed Mohammad
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p. 2322 - 2330
(2020/02/25)
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- Synthesis of lactate derivatives via reductive radical addition to α-oxyacrylates
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Lactate derivatives are important synthetic precursors to a variety of pharmaceutical products. Previously reported methods to prepare lactates require multiple steps or have limited scopes. Herein, we report a Ni-catalyzed reductive addition of a variety
- Diccianni, Justin B.,Chin, Mason,Diao, Tianning
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p. 4180 - 4185
(2019/05/15)
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- Cationic R-Substituted-Indenyl Nickel(II) Complexes of Arsine and Stibine Ligands: Synthesis, Characterization, and Catalytic Behavior in the Oligomerization of Styrene
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A series of new cationic Rn-substituted-indenyl nickel(II) complexes containing arsine or stibine ligands were synthesized in moderate to very high yields by the protonation of the corresponding bis(indenyl) nickel derivatives [Ni(η-Rn-Ind)2] with HBF4, in the presence of 2 equiv. of AsPh3 or SbPh3 donor ligands. These complexes, with the general formula [Ni(η-Rn-Ind)(EPh3)2]BF4 (E = As, Sb), were structurally characterized by NMR spectroscopy and X-ray diffraction, and subsequently tested as single-component catalysts for the oligomerization of styrene, leading to the formation of very low molecular weight head-to-tail oligomers (typically consisting of dimers, trimers and tetramers). The new 1- or 2-monosubstituted-indenyl NiII catalyst precursors exhibit extremely high catalytic activities, considerably higher than those observed for the symmetrical unsubstituted- and the 1,3-disubstituted-indenyl nickel analogues (i.e. monosubstituted >> non-substituted > 1,3-disubstituted), their reactivity pattern showing similarities with that of the corresponding allyl derivatives. A simpler and more straightforward experimental procedure for the high yield preparation of [NiBr2(DME)], an important nickel starting material, which was used in the preparation of the bis(indenyl) nickel precursors of this work, is also described.
- Gomes, Clara S. B.,Costa, Sandra I.,Silva, Leonel C.,Jiménez-Tenorio, Manuel,Valerga, Pedro,Puerta, M. Carmen,Gomes, Pedro T.
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p. 597 - 607
(2018/02/06)
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- 2-(1-Arylimino)quinolylnickel halides: Synthesis, characterization and catalytic behavior towards ethylene
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A series of 2-(1-arylimino)quinolylnickel halides were synthesized and characterized by IR and elemental analyses. Distorted trigonal bipyramidal geometries are adopted for the nickel complexes C1, C4, C7 and C11 as crystallized from either DMF or methanol solution. When activated by Et 2AlCl, the nickel pre-catalysts exhibited good to high catalytic activities in ethylene oligomerization.
- Song, Shengju,Xiao, Tianpengfei,Wang, Lin,Redshaw, Carl,Wang, Fosong,Sun, Wen-Hua
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- Mono- and dinuclear nickel complexes with phosphino-, phosphinito-, and phosphonitopyridine ligands: Synthesis, structures, and catalytic oligomerization of ethylene
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The P,N-type ligands 2-[(diphenylphosphino)methyl]pyridine (12), 2-[2-(diphenylphosphino)ethyl]pyridine (13), 2-methyloxy(diphenylphosphino) pyridine (14), 2-methyloxy(dibenzyl-1,2-oxaphosphorino)pyridine (15), and 2-methyloxy(di-tert-butylphosphino)pyridine (16) have been prepared in good yields, and 12 and 13 have been used to synthesize Ni(II) complexes of formula [Ni(P,N)Cl2], 17 (P,N = 12) and 18 (P,N = 13), by reaction with NiCl2 in methanol. The crystal structure of 18 has been determined by X-ray diffraction to be dinuclear with a distorted square-base pyramidal geometry around the Ni(II) centers. To examine the possible influence of the nature of the spacer link between the P and N donor atoms, we compared ligand 13, with a CH2CH2 spacer, with 14 and 16, which have a isosteric CH2-O spacer. Reactions of the phosphinitopyridine ligands 14 and 16 and of the phosphonitopyridine 15 with [NiX2(DME)] (X = Cl or Br) afforded the complexes [Ni(P,N)Cl2] 20 (X = Cl; P,N = 14), 21 (X = Br; P,N = 14), 22 (X = Cl; P,N = 16), and 23 (X = Cl; P,N = 15), respectively. The mononuclear structure of complex 22 has been established by X-ray diffraction and showed a distorted tetrahedral geometry around the metal center. Complexes 17, 18, and 20-22 have been tested as precatalysts in the oligomerization of ethylene, with AlEtCl2 or MAO as cocatalyst, in order to evaluate the influence of the stereoelectronic properties of the phosphorus substituents. With only 6 equiv of AlEtCl2 as cocatalyst and 4 × 10-5 mol precatalyst, complex 18 was the most active, with turnover frequencies (TOF) up to 91 200 C2H4/(mol Ni·h), and 20 with 2 equiv of AlEtCl2 showed the highest selectivities for ethylene dimers (up to 97%) and in 1-butene (up to 72%). When only 10-5 mol precatalyst was used, the TOF values went up to 207 600 for 18 and 150 100 for 20. With only 25 equiv of MAO as cocatalyst, complex 18 was again the most active, with TOF values up to 20 600 C2H 4/(mpl Ni·h). Despite the high selectivity for C4 olefins of 17, 18, 20, and 21 (up to 93% for 20), 22 presented the best selectivities for 1-butene (up to 73%) with MAO as cocatalyst, and its high reactivity for the reinsertion of 1-butene resulted in 2-ethyl- 1-butene being the main product of the catalytic reaction (up to 91%).
- Kermagoret, Anthony,Braunstein, Pierre
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- Reactivity of Group 10 halides toward (Ph2PN=)C(Ph)[N(SiMe3)2], (NC5H4){(Ph2PN=)C[N(SiMe3) 2]}-4 and C6H4{C(=NPPh2)[N(SiMe3) 2]}2-1,4
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Interaction of [NiBr2(dme)] (dme = 1,2-dimethoxyethane) with 1 equivalent of (Ph2PN=)C(Ph)[N(SiMe3)2] L1 in tetrahydrofuran gave cis-[NiBr2{(Ph2PNH)C(Ph)(=NH)}] 1, metathesis of this compound with excess NH4BF4 in methanol gave cis-[Ni{(Ph2PNH)C(Ph)(=NH)}2][BF4]2 2. Reaction of [NiBr2(dme)] with 1 equivalent of (NC5H4){Ph2PN=)C[N(SiMe3) 2]}-4 L3 followed by metathesis with excess NH4BF4 in methanol gave cis-[Ni{(NC5H4)[(Ph2PNH)C(=NH)]-4} 2[BF4]2 3. Reaction of [PdCl2(PhCN)2] with 1 equivalent of L1 in acetonitrile gave cis-[PdCl2{(Ph2PNH)C(Ph)(=NH)}] 4, and with 0.5 equivalent of C6H4{C(=NPPh2)[N(SiMe3) 2]}2-1,4 L2 in tetrahydrofuran gave cis-[(PdCl2)2{C6H4[C(=NPPh 2){N(SiMe3)2}]2-1,4}] 5 and cis-[(PdCl2)2{C6H4[C(NHPPh 2)-(=NH)]2-1,4}] 6. Interaction of [PdCl2(PhCN)2] with L3 in 1:1 and 3:2 molar ratios gave cis-[PdCl2{(NC5H4)-[(Ph 2PNH)C(=NH)]-4}] 7 and trans-[PdCl2{cis-PdCl2[(NC5H 4){(Ph2PNH)C(=NH)}-4]}2] 8, respectively. Reaction of [MCl2(PhCN)2] (M = Pd or Pt) with 2 equivalents of L3 followed by metathesis with excess NH4BF4 in methanol gave cis-[M{(NC5H4)[(Ph2PNH)C(=NH)]-4}{(NC 5H4)[(Ph2PNH)C(=N)]-4}][BF4] (Pd 9 or Pt 10). Crystal structures of compounds 1, 4, 7, 8, 9 and 10 have been determined.
- Wong, Wai-Kwok,Sun, Chaode,Wong, Wing-Tak
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p. 3387 - 3395
(2007/10/03)
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