- Monomeric three-coordinate N-heterocyclic carbene nickel(I) complexes: Synthesis, structures, and catalytic applications in cross-coupling reactions
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A series of three-coordinate monovalent nickel halide complexes bearing N-heterocyclic carbene (NHC) ligands, i.e., NiCl(IPr)(L) [L = pyridine, P(OPh)3, bis(diphenylphosphino)butane (dppb), IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene], NiX(IMes)(PPh3) (X = Cl and Br, IMes = 1,3-bis(mesityl)imidazol-2-ylidene), were prepared. The complexes were identified using NMR spectroscopy, superconducting quantum interference device (SQUID), and X-ray crystallography. Additionally, ESR spectra of NiCl(IPr)(pyridine) were taken in toluene. These complexes had three-coordinate Y-shaped geometries in both the solid and solution states. The compounds containing IPr showed equilibrium between the monomeric and dimeric forms, with liberation of ligands. Addition of 1,2-bis(diphenylphosphino)ethane and 1,3-bis(diphenylphosphino)propane to the dinickel(I) IPr complex instead of dppb resulted in heterolytic cleavage to nickel(0) and nickel(II) species. Catalysis of Suzuki cross-coupling and Buchwald-Hartwig amination of aryl bromide using the complexes was investigated. The efficiencies in the amination of aryl bromide depended strongly on the additional donor ligands.
- Matsubara, Kouki,Fukahori, Yukino,Inatomi, Takahiro,Tazaki, Saeko,Yamada, Yuji,Koga, Yuji,Kanegawa, Shinji,Nakamura, Toshikazu
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- Diboron-Promoted Reduction of Ni(II) Salts: Precatalyst Activation Studies Relevant to Ni-Catalyzed Borylation Reactions
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The activation and reduction of nickel(II) salts under conditions relevant to Ni-catalyzed borylation reactions is reported. Methanolic solutions of NiCl2·6H2O reacted with >2 equiv of (iPr)2NEt were converted to polymeric Ni(OMe)2, which was characterized by IR spectroscopy, magnetic susceptibility measurements, and verified by independent synthesis from NaOMe. When diboron reagents such as bis(neopentylglycolato) diboron (B2(npg)2) were exposed to methanolic solutions of Ni(II) salts and (iPr)2NEt, nickel metal was deposited along with the evolution of hydrogen gas. A direct relationship between yield of nickel metal and equivalents of B2(npg)2 relative to [Ni] was also observed, reaching >99% yield at 8 equiv. Ni(0) coordination complexes were also isolated when a phosphine, phosphite, and/or diene ligand was present, all starting from NiCl2·6H2O, including the following: Ni[P(OPh)3]4 (74% yield), Ni[P(OiPr)3]4 (54% yield), Ni(PPh3)4 (75% yield), (dppp)2Ni + Ni(1,5-cod)2 (dppp = 1,3-bis(diphenylphosphine)propane) (91% yield), Ni(1,5-cod)2 (1,5-cod = 1,5-cyclooctadiene) (69% yield), and (dppf)Ni(1,5-cod) (dppf = 1,1′-bis(diphenylphosphino)ferrocene) (84% yield). The high yields observed indicated the efficient reduction of Ni(II) to Ni(0) and a likely route for precatalyst entry into the Ni-borylation catalytic cycle. These in situ reduction conditions were also successfully applied to a previously developed Ni-catalyzed alpha-arylation reaction where the requisite Ni(1,5-cod)2 precatalyst was substituted for NiCl2·6H2O and catalytic diboron. Comparable yields to the original report were observed under these conditions, further demonstrating that Ni(0) active species can be efficiently accessed with diboron reagents under protic conditions from Ni(II) salt hydrates.
- Joannou, Matthew V.,Sarjeant, Amy A.,Wisniewski, Steven R.
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p. 2691 - 2700
(2021/08/20)
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- Controlled radical polymerization, and catalysts useful therein
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A catalyst is prepared in situ by reaction between an aryl halide and a Ni(0) complex. The catalyst may be used to promote chain-growth polymerization of halogen-substituted Mg or Zn monomers by a controlled radical mechanism. Polymers, co-polymers, block copolymers, polymer thin films, and surface-confined polymer brushes may be produced using the catalyst.
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Page/Page column 7
(2017/05/31)
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- Synergy between Experimental and Computational Chemistry Reveals the Mechanism of Decomposition of Nickel-Ketene Complexes
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A series of (dppf)Ni(ketene) complexes were synthesized and fully characterized. In the solid state, the complexes possess η2-(C,O) coordination of the ketene in an overall planar configuration. They display similar structure in solution, except in some cases, the η2-(C,C) coordination mode is also detected. A combination of kinetic analysis and DFT calculations reveals the complexes undergo thermal decomposition by isomerization from η2-(C,O) to η2-(C,C) followed by scission of the C=C bond, which is usually rate limiting and results in an intermediate carbonyl carbene complex. Subsequent rearrangement of the carbene ligand is rate limiting for electron poor and sterically large ketenes, and results in a carbonyl alkene complex. The alkene readily dissociates, affording alkenes and (dppf)Ni(CO)2. Computational modeling of the decarbonylation pathway with partial phosphine dissociation reveals the barrier is reduced significantly, explaining the instability of ketene complexes with monodentate phosphines.
- Staudaher, Nicholas D.,Arif, Atta M.,Louie, Janis
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supporting information
p. 14083 - 14091
(2016/11/06)
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- The first catalytic synthesis of an acrylate from CO2 and an alkene-A rational approach
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For more than three decades the catalytic synthesis of acrylates from the cheap and abundantly available C1 building block carbon dioxide and alkenes has been an unsolved problem in catalysis research, both in academia and industry. Herein, we
- Lejkowski, Michael L.,Lindner, Ronald,Kageyama, Takeharu,Bodizs, Gabriella E.,Plessow, Philipp N.,Mueller, Imke B.,Schaefer, Ansgar,Rominger, Frank,Hofmann, Peter,Futter, Cornelia,Schunk, Stephan A.,Limbach, Michael
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supporting information
p. 14017 - 14025
(2013/01/15)
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- Stoichiometric and catalytic reactions of thermally stable nickel(0) NHC complexes
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Although there are many organic reactions that are catalyzed by either Ni0 or Pd0 complexes, in comparison with the case for Pd0 there has been significantly less work studying coordinatively unsaturated Ni0 complexes. Here, we develop a simple synthetic route for preparing a number of thermally stable NHC-supported Ni0 hexadiene complexes in good yield. We examine the stoichiometric reactivity of one of these species and demonstrate that the coordinated hexadiene moiety is labile and can be replaced with a variety of different ligands, including CO, phosphines, isonitriles, and olefins. In addition, we show that the Ni 0 hexadiene complexes are relatively rare examples of homogeneous first-row transition-metal catalysts for the hydrogenation of olefins.
- Wu, Jianguo,Faller, John W.,Hazari, Nilay,Schmeier, Timothy J.
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p. 806 - 809
(2012/05/04)
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- Externally initiated regioregular P3HT with controlled molecular weight and narrow polydispersity
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(Chemical Equation Presented) The ability of chemists to design and synthesize π-conjugated organic polymers with precise control remains the key to technological breakthroughs for using polymer materials in electronic and photonic devices. In this commun
- Bronstein, Hugo A.,Luscombe, Christine K.
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p. 12894 - 12895
(2009/12/05)
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- Syntheses and properties of molecular nickel(II) hydride, methyl, and nickel(I) complexes supported by trimethylphosphane and (2-diphenylphosphanyl)thiophenolato and -naphtholato ligands
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(2-Diphenylphosphanyl)thiophenol (P^pSH) or (3-diphenylphosphanyl)-2-thionaphthol (P^nSH) react with Ni(PMe3)4 to form NiH(P^pS)(PMe3)2 (1) or NiH(P^nS)(PMe3)2 (2). 1,3-Bis(diphenylphosphanyl)propane (P^P) replaces the monodentate phosphane ligands to give NiH(P^pS)(P^P) (3). NiMe(OMe)(PMe3) or NiMe2(PMe3)3 react with P^pSH to form NiMe(P^pS)(PMe3) (4) and NiMe(P^pS)(PMe3)2 (5), respectively, and P^nSH affords NiMe(P^nS)(PMe3)2 (6), NiMe(P^nS)(PMe3) (7). Dissociation of PMe3 ligands induces transformation of 1 to Ni(P^pS)(PMe3)2 (8) and Ni(P^pS)2. Crystal and molecular structures are given for 1, 5-8, and dynamic solution spectra (NMR, EPR) are discussed.
- Kraikivskii, Peter B.,Frey, Markus,Bennour, Hamdi A.,Gembus, Armin,Hauptmann, Ralf,Svoboda, Ingrid,Fuess, Hartmut,Saraev, Vitaly V.,Klein, Hans-Friedrich
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p. 1869 - 1876
(2009/08/14)
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- Mechanistic insights into catalytic H2 oxidation by Ni complexes containing a diphosphine ligand with a positioned amine base
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The mixed-ligand complex [Ni(dppp)(P ph 2 N Bz 2 )](BF 4 ) 2 , 3, (where P ph 2 N Bz 2 is 1,5-dibenzyl-3,7- diphenyl-1,5-diaza-3,7-diphosphacyclooctane and dppp is 1,3- bis(diphenylphosphino)propane) has been synthesized. Treatment of this complex with H 2 and triethylamine results in the formation of the Ni° complex, Ni(dppp)(P ph 2 N Bz 2 ), 4, whose structure has been determined by a single-crystal X-ray diffraction study. Heterolytic cleavage of H 2 by 3 at room temperature forms [HNi(dppp)(P ph 2 N Bz (μ-H)N Bz )](BF 4 ) 2 , 5a, in which one proton interacts with two nitrogen atoms of the cyclic diphosphine ligand and a hydride ligand is bound to nickel. Two intermediates are observed for this reaction using low-temperature NMR spectroscopy. One species isa dihydride, [(H) 2 Ni(dppp)(P ph 2 N Bz 2 )](BF 4 ) 2 , 5b, and the other is [Ni(dppp)(P ph 2 N Bz 2 H 2 )](BF 4 ) 2 , 5c, in which both protons are bound to the N atoms in an endo geometry with respect to nickel. These two species interconvert via a rapid and reversible intramolecularproton exchange between nickel and the nitrogen atoms of the diphosphin e ligand. Complex 3 is a catalyst for the electrochemical oxidation of H 2 in the presence of base, and new insights into the mechani sm derived from low-temperature NMR and thermodynamic studies are presented. A comparison of the rate and thermodynamics of H 2 addition for this complex to related catalysts studied previously indicates that for Ni" complexes containing two diphosphine ligands, the activationof H 2 is favored by the presence of two positioned pendant bases.
- Yang, Jenny Y.,Bullock, R. Morris,Shaw, Wendy J.,Twamley, Brendan,Fraze, Kendra,et al.
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p. 5935 - 5945
(2009/09/25)
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- Nickel-catalysed Substitution Reactions of Allylic Compounds with Soft Nucleophiles: an Efficient Alternative to Palladium Catalysis
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Substitution reactions of allyl alcohol derivatives 1a-c with diethylamine, phenol and dimethyl malonate are efficiently carried out in the presence of Ni(dppb)2 (dppb = 1,2-diphenylphosphinobutane) as catalyst and ammonium salts or bases as promoters or co-reagents.
- Bricout, Herve,Carpentier, Jean-Francois,Mortreux, Andre
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p. 1863 - 1864
(2007/10/02)
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- Effect of the Bite Angle of Diphosphine Ligands on Activity and Selectivity in the Nickel-catalysed Hydrocyanation of Styrene
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The application of diphosphines with large bite angles (βn = 101-109 deg) in nickel catalysts leads to successful, regioselective hydrocyanation of styrene.
- Kranenburg, Mirko,Kamer, Paul C. J.,Leeuwen, Piet W. N. M. van,Vogt, Dieter,Keim, Wilhelm
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p. 2177 - 2178
(2007/10/02)
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- Reactivity of Nickel(II) Diphosphine Complexes towards Alkoxides: a New Route to the Synthesis of Nickel(0) Compounds through Nickel(II) Alkoxides
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Reaction of with NaOR (R = Me, Et or i-Pr) under a dinitrogen atmosphere afforded , Ni(OR)2 and aldehyde (or acetone when R = Pri) in 1:1:1 ratio, showing the peculiar reducing effect of alkoxide promoted by the chelating property of the phosphorus ligand.The reaction of NaOMe with afforded mainly when carried out in the absence of free diphosphine, and in the presence of free diphosphine.The reaction always yields the nickel(0) species when it is carried out under a carbon monoxide atmosphere.The intermediate formation of unstable alkoxo(diphosphine)nickel(II) complexes has been demonstrated by recording the 31P NMR spectra of the reactiong solutions at low temperature; in the case of the reaction of with NaOMe only, it was possible to isolate as a solid the complex, which has been fully characterized by analytical and spectroscopic (IR and 1H, 31P NMR) methods.A possible route by which nickel(0) complexes could be formed is discussed.
- Sacco, Adriano,Mastrorilli, Pietro
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p. 2761 - 2764
(2007/10/02)
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- LIGAND EXCHANGE REACTION BETWEEN NiMe2L2 (L = 1/2 bpy, PEt3) AND DITERTIARY PHOSPHINES Ph2P(CH2)nPPh2 (n = 1-4) AND EFFECT OF LIGAND ON EASE OF REDUCTIVE ELIMINATION OF C2H6 FROM NiMe2(Ph2P(CH2)nPPh2)
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Reactions of the dimethylnickel(II) complexes NiMe2L2 (L = 1/2 bpy, PEt3 (bpy=2,2'-bipyridine)) with diphosphines Ph2P(CH2)nPPh2 (n = 1-4) give NiMe2(Ph2P(CH2)nPPh2) (n = 2, 3) or produce ethane and Ni0-diphosphine complexes (n = 1, 4), depending on the chain length of (CH2)n of the diphosphine ligand employed.The ligand exchange reaction between NiMe2(bpy) and Ph2P(CH2)3PPh2 (dpp) proceeds through an SN2 process with the activation parameters ΔH = 8.3 kcal/mol and ΔS = -35 e.u.A mechanism involving coordination of dpp via one phosphorus atom and ensuing chelation of dpp accompanied by dissociation of bpy is proposed for the ligand exchange reaction.Kinetic studies on the thermal decomposition of NiMe2(Ph2P(CH2)nPPh2) (n = 2, 3) show that the reductive elimination of C2H6 from NiMe2(Ph2P(CH2)nPPh2) (n = 2, 3) proceeds by a unimolecular process with the activation parameters ΔH = 26.8 kcal/mol and ΔS = 1.9 e.u. for NiMe2(Ph2P(CH2)2PPh2) and ΔH = 25.1 kcal/mol and ΔS = 4.8 e.u. for NiMe2(Ph2P(CH2)3PPh2).The rate of reductive elimination of NiMe2(Ph2P(CH2)3PPh2) is 46 times faster than that of NiMe2(Ph2P(CH2)2PPh2) at 64.3 deg C.
- Kohara, Teiji,Yamamoto, Takakazu,Yamamoto, Akio
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p. 265 - 274
(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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