1295-35-8Relevant articles and documents
Preparation of Ni(cod)2 Using Light as the Source of Energy
Ishida, Naoki,Kamae, Yoshiki,Murakami, Masahiro
, p. 1413 - 1416 (2019)
A convenient method to prepare Ni(cod)2 from Ni(acac)2 using light as the source of energy is reported. In the first step of this process, xanthone is reductively dimerized upon irradiation of solar or LED light in 2-propanol to form a vicinal diol possessing a highly sterically congested C-C bond. In the second step, a ketyl radical derived from the diol reacts with Ni(acac)2, ultimately reducing nickel(II) to nickel(0), which is bound by 1,5-cyclooctadiene (COD) to produce Ni(cod)2. This new method obviates the need for hazardous reductants such as diisobutylaluminum hydride (DIBAH) and sodium.
Ethoxycarbonyl-, Cyano- and Methoxy-methyl Complexes of Nickel(II) and their Carbonylation Reactions
Belderrain, Tomas R.,Knight, D. Andrew,Irvine, Derek J.,Paneque, Margarita,Poveda, Manuel L.,Carmona, Ernesto
, p. 1491 - 1496 (1992)
The oxidative addition of ClCH2CO2Et, ClCH2CN and BrCH2OMe to (cod = cycloocta-1,5-diene), in the presence of 2 equivalents of PMe3, affords the β-functionalized nickel(II) methyl derivatives trans- (R = CO2Et, X = Cl 1; R = CN, X = Cl 2; R = OMe, X = Br 3).The interaction of these complexes with carbon monoxide has been studied.The methoxymethyl derivative 3 forms a stable acyl of composition trans- 7, but for the ethoxycarbonylmethyl complex 1 the corresponding acyl 8 forms reversibly and although stable as a solid, only exists in solution under an atmosphere of carbon monoxide.No stable acyl has been observed from the reaction of 2 with CO; only decomposition occurs.Stable 18-electron alkyl and acyl cyclopentadienyl derivatives of composition occurs.Stable 18-electron alkyl and acyl cyclopentadienyl derivatives of composition (R = CO2Et 4; CN 5; or OMe 6) and (R = OMe 9 or CO2Et 10) are easily obtained upon reaction of the above 16-electron complexes with Na(C5H5).The new compounds have been fully characterized by analytical and spectroscopic (IR and 1H, 13C and 31P NMR) methods.
Zur Lewisaciditat von Nickel(0) VII. Alkalimetall-μ3-hydrido-tetrakis(ethen)diniccolat(0)-Komplexe: (pmdta)Li(μ3-H)Ni2(C2H4)4 und (pmdta)Na(μ3-H)Ni2(C2H4)4
Porschke, Klaus Richard,Wilke, Gunther
, p. 257 - 262 (1988)
Ni(C2H4)3 reacts with alkalimetal hydridoaluminates or -gallates MAHA1/GaR3 and MAH2AlR2 (R = alkyl) in ether/pmdta at temperatures between -70 and -20 oC to yield the ion pair complexes (pmdta)MA(μ3-
Soft, Wet-Chemical Synthesis of Metastable Superparamagnetic Hexagonal Close-Packed Nickel Nanoparticles in Different Ionic Liquids
Wegner, Susann,Rutz, Christina,Schütte, Kai,Barthel, Juri,Bushmelev, Alexey,Schmidt, Annette,Dilchert, Katharina,Fischer, Roland A.,Janiak, Christoph
, p. 6330 - 6340 (2017)
The microwave-induced decomposition of bis{N,N′-diisopropylacetamidinate}nickel(II) [Ni{MeC(NiPr)2}2] or bis(1,5-cyclooctadiene)nickel(0) [Ni(COD)2] in imidazolium-, pyridinium-, or thiophenium-based ionic liquids (ILs) with different anions (tetrafluoroborate, [BF4]?, hexafluorophosphate, [PF6]?, and bis(trifluoromethylsulfonyl)imide, [NTf2]?) yields small, uniform nickel nanoparticles (Ni NPs), which are stable in the absence of capping ligands (surfactants) for more than eight weeks. The soft, wet-chemical synthesis yields the metastable Ni hexagonal close-packed (hcp) and not the stable Ni face-centered cubic (fcc) phase. The size of the nickel nanoparticles increases with the molecular volume of the used anions from about 5 nm for [BF4]? to ≈10 nm for [NTf2]? (with 1-alkyl-3-methyl-imidazolium cations). The n-butyl-pyridinium, [BPy]+, cation ILs reproducibly yield very small nickel nanoparticles of 2(±1) nm average diameter. The Ni NPs were characterized by high-resolution transmission electron microscopy (HR-TEM) and powder X-ray diffraction. An X-ray photoelectron spectroscopic (XPS) analysis shows an increase of the binding energy (EB) of the electron from the Ni 2p3/2 orbital of the very small 2(±1) nm diameter Ni particles by about 0.3 eV to EB=853.2 eV compared with bulk Ni0, which is traced to the small cluster size. The Ni nanoparticles show superparamagnetic behavior from 150 K up to room temperature. The saturation magnetization of a Ni (2±1 nm) sample from [BPy][NTf2] is 2.08 A m2 kg?1 and of a Ni (10±4 nm) sample from [LMIm][NTf2] it is 0.99 A m2 kg?1, ([LMIm]=1-lauryl-3-methyl- imidazolium). The Ni NPs were active catalysts in IL dispersions for 1-hexene or benzene hydrogenation. Over 90 % conversion was reached under 5 bar H2 in 1 h at 100 °C for 1-hexene and a turnover frequency (TOF) up to 1330 molhexane (molNi)?1 h?1 or in 60 h at 100 °C for benzene hydrogenation and TOF=23 molcyclohexane (molNi)?1 h?1.
Safe and Expeditious Preparation of Ni(cod)2for Same-Day High-Throughput Screening
Sicard, Alexandre J.,Baker, R. Tom
, p. 2950 - 2952 (2020)
There is an ongoing effort in the catalysis community to replace precious metal catalysts with their base-metal congeners, especially by applied chemists. This is particularly true in the case of nickel and palladium, the latter of which has experienced supply shortages and a concomitant rise in price over the past year. Ni(cod)2 (cod = 1,5-cyclooctadiene) continues to be the flag-bearing precatalyst for nickel-catalyzed transformations on account of its versatility and commercial availability, but is plagued by diseconomies originating from limited shelf life and air/temperature sensitivity. The inconsistent purity of Ni(cod)2 samples over time introduces an element of uncertainty in small-scale catalytic reaction tests such as those employed in high-throughput experimentation (HTE). We provide herein a method by which high-quality 1-g batches of Ni(cod)2 can be prepared easily in 20 min using no pyrophoric reagents, allowing HTE studies with this catalyst to be performed directly after its preparation, reducing such uncertainty.
tmeda-NICKEL-KOMPLEXE. I. (tmeda)Ni(η2-C4H6)2 and 2-C4H6)>2(η2,η2-C4H6)
Schroeder, Wolfgang,Poerschke, Klaus R.
, p. 385 - 392 (1987)
Tris(ethene)nickel(0) reacts with tmeda and butadiene in ether below -40 deg C to yield a deep-red solution of (tmeda)Ni(η2-C4H6)2 (3a), from which red crystals of the thermolabile dinuclear complex 2-C4H6)>2(η2,η2-C4H6) (3b) can be separated.Results in the formation of mononuclear 3a, which also forms upon dissociation of 3b in solution, was identified from its 1H and 13C NMR spectra.Above -40 deg C, 3a,b decompose in solution, with coupling of the butadiene ligands to afford Ni(η3,η3,η2-C12H18), which was shown to be an intermediate of the nickel-catalyzed cyclotrimerisation reaction of butadiene.Thus 3a, b are the first butadiene complexes of nickel that are catalytically active despite the presence of stabilizing ligands.
The Anionic Pathway in the Nickel-Catalysed Cross-Coupling of Aryl Ethers
Borys, Andryj M.,Hevia, Eva
, p. 24659 - 24667 (2021)
The Ni-catalysed cross-coupling of aryl ethers is a powerful method to forge new C?C and C?heteroatom bonds. However, the inert C(sp2)?O bond means that a canonical mechanism that relies on the oxidative addition of the aryl ether to a Ni0 centre is thermodynamically and kinetically unfavourable, which suggests that alternative mechanisms may be involved. Here, we provide spectroscopic and structural insights into the anionic pathway, which relies on the formation of electron-rich hetero-bimetallic nickelates by adding organometallic nucleophiles to a Ni0 centre. Assessing the rich co-complexation chemistry between Ni(COD)2 and PhLi has led to the structures and solution-state chemistry of a diverse family of catalytically competent lithium nickelates being unveiled. In addition, we demonstrate dramatic solvent and donor effects, which suggest that the cooperative activation of the aryl ether substrate by Ni0-ate complexes plays a key role in the catalytic cycle.
Hafnocene-based Bicyclo[2.1.1]hexene Germylenes - Formation, Reactivity, and Structural Flexibility
Dong, Zhaowen,Bedbur, Katja,Schmidtmann, Marc,Müller, Thomas
, p. 3052 - 3060 (2018)
2,5-Disilylsubstituted germole dianions 1 react with hafnocene dichloride to give hafnocene-based bicyclo[2.1.1]hexene germylenes 3. Their formation proceeds via hafnocene-germylene complexes 2 that were identified by NMR and UV spectroscopy. Germylenes 3 are stabilized by homoconjugation between the empty 4p(Ge) orbital and the ?€-bond of the innercyclic C2? - C3 double bond. This interaction can be understood as σ2, ?€-coordination of the butadiene part to the dicoordinated germanium atom that leaves the 16e- hafnocene moiety electronically unsaturated. We demonstrate that this new class of germylenes might serve as ligand to a variety of low-valent transition-metal complexes. The structure of the germylene ligand in complexes with Fe(0), Ni(0), and Au(I) and in reaction products with N-heterocyclic carbenes showed an intriguing structural flexibility that allows to accommodate different electronic situations at the ligating germanium atom. The origin of this structural adaptability is the interplay between the topological flexible unsaturated germanium ring and the hafnocene group.
Allylnickel(II) complexes of bulky 5-substituted-2-iminopyrrolyl ligands
Cruz, Tiago F. C.,Gomes, Pedro T.,Lopes, Patrícia S.
, (2021)
The optimized reaction between [Ni(COD)2] (COD = 1,5-cyclooctadiene) and ligand precursor 5-(2,4,6-triisopropylphenyl)-2-[N-(2,6-diisopropylphenyl)-formimino]-1H-pyrrole yielded the η3-cyclooctenyl-Ni(II) complex [Ni{κ2N,N’-5-(2,4,6-iPr3C6H2)-NC4H2-2-C(H) = N(2,6-iPr2C6H3)}(η3-C8H13)] 1. Subsequently, the η3-allyl complexes [Ni{κ2N,N’-5-R-NC4H2-2-C(H)=N(2,6-iPr2C6H3)}(η3-C3H5)] (R = 3,5-(CF3)2C6H3 (2a), 2,6-Me2C6H3 (2b), 2,4,6-iPr3C6H2 (2c) and CPh3 (2d)) were prepared in good yields via metathesis of [Ni(η3-C3H5)(μ-Br)]2 with the respective potassium 5-R-2-[N-(2,6-diisopropylphenyl)formimino]pyrrolyl salt (KLa-d). Complexes 1 and 2a-d were characterized by NMR spectroscopy, elemental analysis and complex 2d further analyzed by single crystal X-ray diffraction. Addition of excess pyridine to solutions of complexes 2a-d led to the observation of a fluxional process that, according to VT-NMR experiments, corresponds to a pyridine-assisted cis–trans isomerization process occurring in these complexes, via a η3-η1-η3 haptotropic shift of the allyl ligand, with ΔG? values in range of 9.5–17.3 kcal mol?1. Additionally, complexes 2a-d, when activated by B(C6F5)3, slowly catalyzed the isomerization of hex-1-ene to mixtures of internal olefins.
16-Electron Nickel(0)-Olefin Complexes in Low-Temperature C(sp2)-C(sp3) Kumada Cross-Couplings
Lutz, Sigrid,Nattmann, Lukas,N?thling, Nils,Cornella, Josep
supporting information, p. 2220 - 2230 (2021/05/07)
Investigations into the mechanism of the low-temperature C(sp2)-C(sp3) Kumada cross-coupling catalyzed by highly reduced nickel-olefin-lithium complexes revealed that 16-electron tris(olefin)nickel(0) complexes are competent catalysts for this transformation. A survey of various nickel(0)-olefin complexes identified Ni(nor)3as an active catalyst, with performance comparable to that of the previously described Ni-olefin-lithium precatalyst. We demonstrate that Ni(nor)3, however, is unable to undergo oxidative addition to the corresponding C(sp2)-Br bond at low temperatures (a nickel(0)-alkylmagnesium complex. We demonstrate that this unique heterobimetallic complex is now primed for reactivity, thus cleaving the C(sp2)-Br bond and ultimately delivering the C(sp2)-C(sp3) bond in high yields.
