- Preparation of Ni(cod)2 Using Light as the Source of Energy
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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.
- Ishida, Naoki,Kamae, Yoshiki,Murakami, Masahiro
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- Ethoxycarbonyl-, Cyano- and Methoxy-methyl Complexes of Nickel(II) and their Carbonylation Reactions
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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.
- Belderrain, Tomas R.,Knight, D. Andrew,Irvine, Derek J.,Paneque, Margarita,Poveda, Manuel L.,Carmona, Ernesto
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- 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
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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-
- Porschke, Klaus Richard,Wilke, Gunther
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- Soft, Wet-Chemical Synthesis of Metastable Superparamagnetic Hexagonal Close-Packed Nickel Nanoparticles in Different Ionic Liquids
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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.
- Wegner, Susann,Rutz, Christina,Schütte, Kai,Barthel, Juri,Bushmelev, Alexey,Schmidt, Annette,Dilchert, Katharina,Fischer, Roland A.,Janiak, Christoph
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- Safe and Expeditious Preparation of Ni(cod)2for Same-Day High-Throughput Screening
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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.
- Sicard, Alexandre J.,Baker, R. Tom
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- tmeda-NICKEL-KOMPLEXE. I. (tmeda)Ni(η2-C4H6)2 and 2-C4H6)>2(η2,η2-C4H6)
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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.
- Schroeder, Wolfgang,Poerschke, Klaus R.
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- The Anionic Pathway in the Nickel-Catalysed Cross-Coupling of Aryl Ethers
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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.
- Borys, Andryj M.,Hevia, Eva
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- Hafnocene-based Bicyclo[2.1.1]hexene Germylenes - Formation, Reactivity, and Structural Flexibility
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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.
- Dong, Zhaowen,Bedbur, Katja,Schmidtmann, Marc,Müller, Thomas
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- Allylnickel(II) complexes of bulky 5-substituted-2-iminopyrrolyl ligands
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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.
- Cruz, Tiago F. C.,Gomes, Pedro T.,Lopes, Patrícia S.
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- Preparation method of bilastine key intermediate
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The invention belongs to the technical field of drug synthesis, and relates to 2 - (4 - (2 - (4 -ethoxyethyl) 1 - benzo [2 -] imidazol - 1H - yl) piperi d-ethyl) phenyl) -2 -methylpropionate (-1 -), and a -2 - complex and II acid are used as a catalyst to condensation the enolate anion with the compound (16 15) to form a target product II Ni Lewis. The invention aims to provide a short synthetic route. The provided route raw material condition is mild, the yield is high, the tedious building quaternary carbon atom method reported in the traditional process is avoided, and the method is suitable for industrial production.
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Paragraph 0040-0041
(2021/08/25)
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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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- 16-Electron Nickel(0)-Olefin Complexes in Low-Temperature C(sp2)-C(sp3) Kumada Cross-Couplings
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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.
- Lutz, Sigrid,Nattmann, Lukas,N?thling, Nils,Cornella, Josep
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supporting information
p. 2220 - 2230
(2021/05/07)
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- Role of the X Coligands in Cyclometalated [Ni(Phbpy)X] Complexes (HPhbpy = 6-Phenyl-2,2′-bipyridine)
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The coligand X was varied in the organonickel complexes [Ni(Phbpy)X] (X = F, Cl, Br, I, C6F5) carrying the anionic tridentate CNN ligand 6-(phen-2-ide)-2,2′-bipyridine (Phbpy-) to study its effect on electronic structures of these complexes and their activity in Negishi-like C-C cross-coupling catalysis. The complexes were synthesized from the precursor [Ni(COD)2] (COD = 1,5-cyclooctadiene) by chelate-assisted oxidative addition into the phenyl C-X bond of the protoligand 6-(2-halidophenyl)-2,2′-bipyridine) and were obtained as red powders. Protoligands X-Phbpy carrying the halide surrogates X = OMe, OTf (triflate) failed in this reaction. Single-crystal XRD allowed us to add the structures of [Ni(Phbpy)Cl] and [Ni(Phbpy)I] to the previously reported Br derivative. Cyclic voltammetry showed reversible reductions for X = C6F5, F, Cl, while for Br and I the reversibility is reduced through rapid splitting of X- after reduction (EC mechanism). UV-vis spectroelectrochemistry confirmed the decreasing degree of reversibility along the series C6F5 > F > Cl ? Br > I, which parallels the "leaving group character"of the X coligands. This method also revealed mainly bpy centered reduction and essentially Ni(II)/Ni(III) oxidations, as corroborated by DFT calculations. The rather X-invariant long-wavelength UV-vis absorptions and excited states were analyzed in detail using TD-DFT and were consistent with predominant metal to ligand charge transfer (MLCT) character. Initial catalytic tests under Negishi-like conditions showed the complexes to be active as catalysts in C-C cross-coupling reactions but did not display marked differences along the series from Ni-F to Ni-I.
- Chin, Mason T.,H?rner, Gerald,Klein, Axel,Kletsch, Lukas,Sandleben, Aaron,Sch?fer, Sascha,Vicic, David A.,Vogt, Nicolas
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supporting information
p. 1776 - 1785
(2021/06/28)
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- Cationic nickel(II)-catalyzed hydrosilylation of alkenes: Role of p, n?type ligand scaffold on selectivity and reactivity
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Seven structurally similar cationic nickel(II)?alkyl complexes were synthesized by using a series of P, N ligands, and their reactivity was explored in the hydrosilylation of alkenes. More electron-rich phosphines enhanced the overall reactivity of the transformation; in contrast, groups on the imine donor had little impact. Overall, these catalysts displayed reactivity and selectivity that was previously unknown or very rare in nickel-catalyzed hydrosilylation. In reactions with Ph2SiH2, 1,2-disubstituted vinylarenes showed complete benzylic selectivity for silane addition, whereas terminal selectivity was observed for 1,1-disubstituted alkenes. The related PhSiH3 led to exclusively Markovnikov selectivity for monosubstituted vinylarenes with no competing double addition observed. Mechanistic investigations supported the hypothesis that a Ni?H functions as the active species in this catalytic hydrosilylation, which in turn also showed catalytic competence for the silane redistribution reaction, especially with sterically unhindered silanes.
- Hossain, Istiak,Schmidt, Joseph A.R.
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supporting information
p. 3441 - 3451
(2020/10/09)
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- Simplified and versatile access to low valent Ni complexes by metal-free reduction of NiII precursors
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The reduction of [Ni(DME)Cl2] with 2 equiv. of bis(trimethylsilyl)-1,4-tetramethyldihydropyrazine in the presence of a ligand L and an excess of olefin cleanly leads to [Ni(L)(alkene)2] complexes. When reduction is performed in the presence of 1,5-cyclooctadiene (COD), [Ni(COD)2] is obtained. Such an approach also allows access to the NiI dimer [Ni(bis(dicyclohexylphosphino)propane)Cl]2.
- Moser, Emile,Jeanneau, Erwann,Mézailles, Nicolas,Olivier-Bourbigou, Hélène,Breuil, Pierre-Alain R.
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supporting information
p. 4101 - 4104
(2019/04/01)
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- Redox Series of Cyclometalated Nickel Complexes [Ni((R)Ph(R′)bpy)Br]+/0/-/2- (H-(R)Ph(R′)bpy = Substituted 6-Phenyl-2,2′-bipyridine)
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New organonickel complexes [Ni((R)Ph(R′)bpy)Br] carrying various substituted derivatives of the tridentate -C∧N∧N ligand 6-(phenyl-2-ide)-2,2′-bipyridine (-Phbpy) were synthesized from the precursor [Ni(COD)2] (COD = 1,5-cyclooctadiene) and the protoligands (ligand precursors) Br-(R)Ph(R′)bpy. Several synthetic routes for the protoligands were studied and compared. All new compounds have been analyzed and spectroscopically characterized. From several complexes crystal and molecular structures were obtained from XRD experiments. UV-vis absorption spectroscopy and detailed electrochemical measurements reveal the impact of the various substituents on the electronic structure of the complexes. Quantum chemical DFT calculations illustrate the composition of highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) and support the assignment of the single-electron reduction and oxidation products as bpy-localized ligand radical species and transient nickel(III) intermediates, respectively.
- Sandleben, Aaron,Vogt, Nicolas,H?rner, Gerald,Klein, Axel
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supporting information
p. 3332 - 3341
(2018/09/27)
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- Air-stable nickel precatalysts for fast and quantitative cross-coupling of aryl sulfamates with aryl neopentylglycolboronates at room temperature
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A library containing 10 air-stable NiIIX(Aryl)(PCy3)2 complexes as precatalysts (X = Cl, Br, OTs, OMs, aryl = 1-naphthyl, 2-naphthyl; X = Cl, 1-acenaphthenyl, 1-(2-methoxynaphthyl), 9-phenanthrenyl, 9-anthracyl) was synthesized and demonstrated to quantitatively cross-couple 2-methoxyphenyl dimethylsulfamate with methyl 4-(5,5-dimethyl-1,3,2-dioxaborinane-2-yl)benzoate at 23 °C in dry THF in the presence of K3PO4(H2O)3.2 in less than 60 min. Lower or higher amounts of H2O in K3PO4 and as received THF mediate the same transformation in a maximum three times longer reaction time.
- Jezorek, Ryan L.,Zhang, Na,Leowanawat, Pawaret,Bunner, Matthew H.,Gutsche, Nicholas,Pesti, Aleksander K. R.,Olsen, James T.,Percec, Virgil
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supporting information
p. 6326 - 6329
(2015/02/19)
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- Chemoselective hydrosilylation of hydroxyketones
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A chemoselective method for the hydrosilylation of ketones has been developed, using the combination of triphenylsilane and a catalyst prepared from Ni(COD)2 and the simple N-heterocyclic carbene IMes. The most notable feature of this method is that free hydroxyls are largely unaffected, thus providing a simple one-step procedure for the conversion of hydroxyketones to mono-protected diols, wherein the protecting group is exclusively installed on the ketone-derived hydroxyl. The process is typically high yielding with both simple ketones and more complex hydroxyketone substrates.
- Lage, Marta L.,Bader, Scott J.,Sa-Ei, Kanicha,Montgomery, John
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p. 5609 - 5613
(2013/07/11)
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- [3+3] cyclodimerization of methylenecyclopropanes: Stoichiometric and catalytic reactions of Nickel(0) with electron-deficient alkylidenecyclopropanes
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Stoichiometric treatment of Ni(cod)2 with ethyl cyclopropylideneacetate (ECPA) in the presence of PCy3 resulted in an unpredicted formation of a Ni(0) complex bearing an (E,E)-1,2-bis(exo- alkylidene)cyclohexane ligand, which stemmed from the [3 + 3] cyclodimerization of ECPA. The reaction could be expanded to a Ni(0)-catalyzed [3 + 3] cyclodimerization reaction of ester-substituted methylenecyclopropanes, giving the corresponding cyclohexane derivatives in excellent yields.
- Ohashi, Masato,Taniguchi, Tomoaki,Ogoshi, Sensuke
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p. 2386 - 2389
(2010/08/05)
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- Reversible carbon-carbon bond formation between 1,3-dienes and aldehyde or ketone on nickel(0)
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The reversible oxidative cyclization of dienes and aldehydes with nickel(0) proceeded to give η3:η1-allylalkoxynickel complexes. The treatment of these complexes with carbon monoxide led to the formation of the corresponding lactone and/or the regeneration of a butadiene and an aldehyde concomitant with the formation of Ni(CO)3(PCy 3). The scission of the nickel-oxygen bond of the allylalkoxy complexes with ZnMe2 leading to η3-allyl(methyl)nickel was very efficient to suppress the reverse reaction of the oxidative cyclization. The methylated η3-allylnickel compound underwent the reductive elimination. The carbonylative coupling reaction of the η3-allyl(methyl)nickel proceeded as well under a carbon monoxide atmosphere. Similarly, the addition of Me3SiCl to η3:η1-allylalkoxynickel complexes was also efficient for the inhibition of the reverse reaction. The resulting η3-1-siloxyethylallylnickel complex was treated with carbon monoxides followed by the addition of MeOH to give the expected hydroxyester. This method is efficient as well even for the η3: η1-allyl(alkoxy)nickel complex containing acetone as a component, which was so prone to undergo the reverse reaction hampering its isolation. The isolation of the η3:η1-allylalkoxynickel complex containing ketone as a component was made easier by the use of heavier butadiene and ketone, such as 2,3-dibenzyl-1,3-butadiene and benzophenone or by the use of cyclobutanone. The reaction with styrene oxide gave the η3: η1-allylalkoxynickel containing phenylacetoaldehyde, an isomer of styrene oxide.
- Ogoshi, Sensuke,Tonomori, Kei-Ichi,Oka, Masa-Aki,Kurosawa, Hideo
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p. 7077 - 7086
(2007/10/03)
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- Structural characterisation of cationic methylallyl, methylindenyl and pentamethylcyclopentadienyl nickel complexes containing the bulky phosphine 1,2-bis(diisopropylphosphino)ethane
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A novel high-yield, convenient synthetic method for the complex [Ni(COD)2] has been developed based upon the use of dibutylmagnesium as reducing agent. The cationic complexes [Ni(η3CH2C(R)CH2)(dippe)][BPh4] (R = Me la or H 1b; dippe = Pr2iPCH2CH2PPr2i ) were obtained by reaction of [Ni(COD)2] with BrCH2C(R)=CH2 in diethyl ether, followed by treatment with dippe and NaBPh4 in methanol. [Ni(2-MeInd)(dippe)][BPh4] 2 (2-MeInd = 2-methylindenyl) and [Ni(C5Me5)(dippe)][BPh4] 3 were respectively prepared by reaction of either [Ni(2-MeInd)Br(PPh3] or [Ni(C5Me5)Br(PPh3)] with dippe and NaBPh4 in methanol. The crystal structures of 1a, 2 and 3 were determined. All of the compounds show pseudo-square planar two legged piano stool structures. The methylallyl ligand in la shows η3 coordination as expected, whereas in 2 the occurrence of an allyl-ene distortion in the 2-methylindenyl ligand leads to an intermediate η3η5 coordination mode. An intermediate allyl-ene/diene distortion is present in the C5Me5 ligand in 3, although in this case a symmetrical η5 coordination is observed. All compounds were also characterised in solution by NMR spectroscopy.
- Tenorio, Manuel Jimenez,Puerta, M. Carmen,Salcedo, Isabel,Valegra, Pedro
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- The preparation of finely divided metal powders and transition metal complexes using organically solvated magnesium
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Treatment of commercial magnesium powder in THF with a small amount of anthracene generates a highly active form of magnesium (Mg*).The Mg* is an excellent in situ reducing agent for transition metal salts, giving highly reactive metal powders of Groups 8-12.In the presence of electron donor ligands, this reduction provides a useful one-step route to organotransition metal complexes.The application of 35 kHz ultrasound during the reaction improves the dispersity of the metal powders and enhances the yields of the complexes.
- Boennemann, Helmut,Bogdanovic, Borislav,Brinkmann, Rainer,Spliethoff, Bernd,He, Da-Wei
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- TRANSITION METAL ALLYLS VI. THE STOICHIOMETRIC REACTION OF 1,3-DIENES WITH LIGAND MODIFIED ZEROVALENT-NICKEL SYSTEMS
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Butadiene and methylsubstituted 1,3-dienes react with zerovalent-nickel-ligand complexes in a stoichiometric manner to give octadiendylnickel-ligand complexes.The structure, rearrangement and reactions with CO and P-donor ligands of these species have been studied with the help of 1H and 13C NMR spectroscopy.The results provide an insight into the mechanism of the nickel-catalyesd cyclodimerization of 1,3-dienes.
- Benn, R.,Buessemeier, B.,Holle, S.,Jolly, P. W.,Mynott, R.,et all.
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- On the Lewis Acidity of Nickel(0), I: Methyllithium Complexes of Nickel(0)
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The synthesis and properties of the methyllithium complexes of nickel(0) of the type (n-Donor)m-(LiCH3)Ni0(?-Ligand)n (1a-c, 16a-c, 20a-c) are described.The structure of (PMDTA)(LiCH3)Ni(C2H4)2 (1b) has been determined by X-ray crystallography. - In these ate complexes, a carbanionic methyl group is ?-bonded to a nickel atom, the acceptor strength of which depend on the ?-ligands.The chemical and spectroscopic properties indicate that the Ni-CH3 bond in the carbonyl complex is largely covalent whereas in the CDT and ethene compounds it is more polar.The CDT complex is thermolabile in solution.The findings are in agreement with the following series of increasing acceptor strength: Ni(CDT) Ni(C2H4)2 Ni(CO)3.
- Poerschke, Klaus-Richard,Jonas, Klaus,Wilke, Guenther,Benn, Reinhard,Mynott, Richard,et al.
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p. 275 - 297
(2007/10/02)
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- Cyclapriftdtonylnlckel cydoodadlorne: A stable orgenornetallic π radical containing a nonconjugated polyolefln
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Reduction of cyclopentadlenylnlckel cyclooctadlene cation, CpNlCod+, in which the polyolefin ring la bonded as a nonconjugated diene to the metal, has been aocompltehed electrochemlcaily in weakly polar nonaqueous mada.
- Lane, Grogg,Gelger, William E.
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p. 401 - 402
(2008/10/08)
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