- Oxidatively induced carbon-halogen bond-forming reactions at nickel
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This communication describes the first reported example of carbon-halogen bond formation from an isolable nickel aryl halide precursor. In addition, oxidatively induced Ar-Br bond-forming reactions from the nickel(II) complex NiII(phpy)(Br)(pic
- Higgs, Andrew T.,Zinn, Paul J.,Simmons, Sarah J.,Sanford, Melanie S.
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- Halogen Photoelimination from Monomeric Nickel(III) Complexes Enabled by the Secondary Coordination Sphere
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Endothermic halogen elimination reactions, in which molecular halogen photoproducts are generated in the absence of chemical traps, are rare. Inspired by the proclivity of mononuclear Ni(III) complexes to participate in challenging bond-forming reactions in organometallic chemistry, we targeted Ni(III) trihalide complexes as platforms to explore halogen photoelimination. A suite of Ni(III) trihalide complexes supported by bidentate phosphine ligands has been synthesized and characterized. Multinuclear NMR, EPR, and electronic absorption spectroscopies, as well as single-crystal X-ray diffraction, have been utilized to characterize this suite of complexes as distorted square pyramidal, S = 1/2 mononuclear Ni(III) complexes. All complexes participate in clean halogen photoelimination in solution and in the solid state. Evolved halogen has been characterized by mass spectrometry and quantified chemically. Energy storage via halogen elimination was established by solution-phase calorimetry measurements; in all cases, halogen elimination is substantially endothermic. Time-resolved photochemical experiments have revealed a relatively long-lived photointermediate, which we assign to be a Ni(II) complex in which the photoextruded chlorine radical interacts with a ligand-based aryl group. Computational studies suggest that the observed intermediate arises from a dissociative LMCT excited state. The participation of secondary coordination sphere interactions to suppress back-reactions is an attractive design element in the development of energy-storing halogen photoelimination involving first-row transition metal complexes.
- Hwang, Seung Jun,Anderson, Bryce L.,Powers, David C.,Maher, Andrew G.,Hadt, Ryan G.,Nocera, Daniel G.
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p. 4766 - 4774
(2015/10/28)
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- Iminobisphosphines to (Non-)symmetrical diphosphinoamine ligands: Metal-induced synthesis of diphosphorus nickel complexes and application in ethylene oligomerisation reactions
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We describe the synthesis of a range of novel iminobisphosphine ligands based on a sulfonamido moiety [R1SO2N=P(R2)2-P(R3)2]. These molecules rearrange in the presence of nickel by metal-induced breakage of the P-P bond to yield symmetrical and nonsymmetrical diphosphinoamine nickel complexes of general formula Ni{[P(R2)2]N(SO2R1)P(R3)2}Br2. The complexes can be isolated and are very stable. Upon activation by MAO, these complexes oligomerise ethylene to small chain oligomers (mainly C4-C8) with high productivity. Surprisingly fast codimerisation reactions of ethylene with butenes is observed, leading to a high content of branched C6 products.
- Boulens, Pierre,Lutz, Martin,Jeanneau, Erwann,Olivier-Bourbigou, Hlne,Reek, Joost N. H.,Breuil, Pierre-Alain R.
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p. 3754 - 3762
(2015/05/05)
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- Trap-Free Halogen Photoelimination from Mononuclear Ni(III) Complexes
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Halogen photoelimination reactions constitute the oxidative half-reaction of closed HX-splitting energy storage cycles. Here, we report high-yielding, endothermic Cl2 photoelimination chemistry from mononuclear Ni(III) complexes. On the basis of time-resolved spectroscopy and steady-state photocrystallography experiments, a mechanism involving ligand-assisted halogen elimination is proposed. Employing ancillary ligands to promote elimination offers a strategy to circumvent the inherently short-lived excited states of 3d metal complexes for the activation of thermodynamically challenging bonds.
- Hwang, Seung Jun,Powers, David C.,Maher, Andrew G.,Anderson, Bryce L.,Hadt, Ryan G.,Zheng, Shao-Liang,Chen, Yu-Sheng,Nocera, Daniel G.
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supporting information
p. 6472 - 6475
(2015/06/08)
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- Halogenolysis of a nickelalactone complex produces β-halo-anhydrides
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Nickelalactone complex [(dppe)Ni{κ2-C,O-CH2CH2C(=O)O}] {dppe = 1,2-bis(diphenylphosphino)ethane} reacts with halogens to form 3-halo-propionic anhydrides, [(dppe)NiX2], and [(dppeO2)3Ni][NiX4] (X = Cl, Br, I). Studies of model complexes [(dppe)Ni(O2CtBu)2] and [(dppe)NiBr(O2CtBu)] suggest that oxidation to NiIII and P-O reductive elimination are key steps in this reaction.
- Zarkesh, Ryan A.,Hopkins, Michael D.,Jordan, Richard F.
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p. 5491 - 5494
(2015/03/30)
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- σ-bond metathesis between M-X and RC(O)X′ (M = Pt, Pd; X, X′ = Cl, Br, I): Facile determination of the relative Δ G values of the oxidative additions of RC(O)X to an M(0) complex, evidence by density functional theory calculations, and synthetic applications
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The novel utility of the ligand exchange reaction between M-X and RC(O)X′ (X, X′ = halogen; R = aryl, alkyl) is described. The relative ΔGs (ΔΔGs) of the oxidative additions of acid halides RC(O)X to M(PPh3)2Ln (M = Pt, Pd) were determined using the halogen-exchange reactions between X of trans-M(X)[C(O)R](PPh3)2 and X′ of RC(O)X′. Experimental thermodynamics data are reasonably consistent with those obtained by density functional theory (DFT) calculations. Activation parameters obtained by experiments as well as a systematic DFT study supported the fact that reactions occurred through slightly distorted quadrangular pentacoordinated σ-bond metatheses, in which the Cl atom underwent a more indirect course than the Br atom. Moreover, exchange reactions were employed as the accessible prototype for the conversion of halogen ligands of nickel triad complexes into heavier halogen ligands.
- Kuniyasu, Hitoshi,Sanagawa, Atsushi,Nakane, Daisuke,Iwasaki, Takanori,Kambe, Nobuaki,Bobuatong, Karan,Lu, Yunpeng,Ehara, Masahiro
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supporting information
p. 2026 - 2032
(2013/05/09)
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- N,N′-Di(alkyloxy)imidazolium Salts: New patent-free ionic liquids and NHC precatalysts
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I-Hydroxyimidazole-3-oxides (2-H, 2-Me) were alkylated with (RO) 2SO2 (R = Me, Et) to give the new 1,3-di(alkyloxy) imidazolium cations which were isolated as hexafluorophosphates. Ion metathesis yielded new hydrophobic ionic liquids
- Laus, Gerhard,Schw?rzler, Alexander,Schuster, Philipp,Bentivoglio, Gino,Hummel, Michael,Wurst, Klaus,Kahlenberg, Volker,L?rting, Thomas,Schütz, Johannes,Peringer, Paul,Bonn, Günther,Nauer, Gerhard,Schottenberger, Herwig
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p. 295 - 308
(2008/10/09)
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- Reactions between Bis(O-alkyl dithiocarbonato)nickel(II) Complexes and Phosphines. Formation of a Dithiocarbonate Complex of Nickel(II):
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The behaviour of O-alkyl dithiocarbonato complexes, , towards several phosphines has been studied.Depending on the S2COR derivative and phosphine (L) used, octahedral complexes , paramagnetic five-co-ordinate complexes , and square-planar (R=Et or cyclo-C6H11) and complexes have been obtained.The reaction of (R=Me, Et, or cyclo-C6H11) with an excess of dppe gives which is the first NiII-dithiocarbonate complex described.This compound reacts with MeI and C3H5Br to give (X=I or Br).There is no reaction with Lewis-base N donors or with carbon monoxide.
- Perpinan, Maria F.,Ballester, Loreto,Gonzalez-Casso, Maria E.,Santos, Amelia
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p. 281 - 284
(2007/10/02)
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- Reactions of Dialkylnickel(II) Complexes NiR2L2 with Alkyl (or Aryl) Halides, R'COY (Y=Cl, Br, OPh, OCOPh), and CS2
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Reactions of Ni(CH3)2(bpy) (1), Ni(C2H5)2(bpy) (2) (bpy=2,2'-bipyridine), trans-Ni(CH3)2(triethylphosphine)2 (3), Ni(CH3)2(1,2-bis(diphenylphosphino)ethane) (4), and Ni(CH3)2(1,3-bis(diphenylphosphino)propane) (5) with alkyl or aryl halides, R'COY (Y=Cl, Br, OC6H5, OCOC6H5), and CS2 have been investigated.The reactions of NiR2L2 with alkyl or aryl halides are classified into three types of reactions by their reaction products: Type A: NiR2L2 + R'X ->NiX(R')L2 + R-R, Type B: NiR2L2 + R'X -> alkane (RH) + olefin (R'(-H)), and Type C: NiR2L2 + R'X -> NiR(X)L2 + R-R'.Complexes 1 and 2 undergo mainly Type A reaction.Complex 3 gives Type A reaction product on treatment with C6H5Br, but it gives Type B reaction product on treatment with C2H5Br.On the other hand, 4 undergoes Type C reaction on interaction with C6H5Cl.The reactions with R'COY (Y=Cl, Br, OPh, OCOPh) are classiffed into two types of reactions by their reaction products: Type D: NiR2L2 + R'COY -> NiY(R)L2 + RCOR' and Type E: NiR2L2 + R'COY -> NiY(R')L2 + RCOR.Complexes 1-3 undergo mainly Type D reaction, whereas complexes 4 and 5 mainly Type E reaction.The diffrence in the reaction route is discussed on the basis of presence or absence of vacant coordination site for attack by R'COY.The reaction of 4 with CS2 affords Ni(CS2)(1,2-bis(diphenylphoshino)ethane) with evolution of a reductive elimination product, ethane, whereas the reaction of 3 with CS2 gives a 1:1 adduct of 3 and CS2.
- Yamamoto, Takakazu,Kohara, Teiji,Osakada, Kohtaro,Yamamoto, Akio
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p. 2147 - 2153
(2007/10/02)
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- Ditertiary phosphine complexes of nickel. Spectral, magnetic, and proton resonance studies. A planar-tetrahedral equilibrium
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A number of complexes of nickel in oxidation states 0, II, and III with the ditertiary phosphines (C6H5)2P(CH2)nP(C 6H5)2 (n = 1, 2, or 3) are reported and studied by spectral and magnetic methods. In solution in organic solvents complexes of the type Ni[(C6H5)2P(CH2)nP(C 6H5)2]X2 where X = Br or I and n = 2 remain diamagnetic. The analogous complexes with n = 3 show a square-planar (diamagnetic)-tetrahedral (paramagnetic) equilibrium in solution. Isotropic proton magnetic resonance shifts were observed in these systems and thermodynamic parameters for the equilibrium were obtained from the temperature dependences of these shifts. The epr spectrum of polycrystalline Ni[(C6H5)2P(CH2)3P(C 6H5)2]Br3 shows an isotropic signal at g = 2.218.
- Van Hecke, Gerald R.,Horrocks Jr., William DeW.
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p. 1968 - 1974
(2008/10/08)
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