Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Nickel complexes arene

Trifluorophosphine is a very convenient ligand in metal atom chemistry to use along with other ligands, e.g., in the stabilization of metal arene complexes (Section III,B). Reaction of a mixture of PF3 and PH3 with nickel vapor yields Ni(PF3)3PH3 and Ni(PF3)2(PH3)2 but no Ni(PH3)4. Attempts to make Ni(PH3)4 lead to hydrogen evolution from the ligand during or after condensation with the nickel vapor (128). [Pg.65]

Manganese, iron, cobalt, and nickel vapors do not give arene complexes with haloarenes. Interactions with hexafluorobenzene have been reported, but the explosive products are unlikely to be complexes containing planar C8F8 rings. The Ni-C8F8 cocondensate is a source of... [Pg.75]

C-M bond addition, for C-C bond formation, 10, 403-491 iridium additions, 10, 456 nickel additions, 10, 463 niobium additions, 10, 427 osmium additions, 10, 445 palladium additions, 10, 468 rhodium additions, 10, 455 ruthenium additions, 10, 444 Sc and Y additions, 10, 405 tantalum additions, 10, 429 titanium additions, 10, 421 vanadium additions, 10, 426 zirconium additions, 10, 424 Carbon-oxygen bond formation via alkyne hydration, 10, 678 for aryl and alkenyl ethers, 10, 650 via cobalt-mediated propargylic etherification, 10, 665 Cu-mediated, with borons, 9, 219 cycloetherification, 10, 673 etherification, 10, 669, 10, 685 via hydro- and alkylative alkoxylation, 10, 683 via inter- andd intramolecular hydroalkoxylation, 10, 672 via metal vinylidenes, 10, 676 via SnI and S Z processes, 10, 684 via transition metal rc-arene complexes, 10, 685 via transition metal-mediated etherification, overview,... [Pg.76]

Supramolecular catalysis may also involve the combination of a host cavity and a metal active site as in the bis(diphenylphosphino)calix[4]arene nickel(II) complex 12.40 which acts as an efficient catalyst for ethylene and propylene polymerisation, and in tandem with zirconocene dichloride, for the formation of linear low-density polyethylene. In the latter case the complex gives very little branching - a significant advantage. The key to the effectiveness of the catalyst involves calixarene-induced changes in the bite angle at the Ni(II) centre, which is square planar in the active form of the catalyst.29... [Pg.847]

Semeril, D., Lejeune, M., Matt, D., Calix [4] arene-derived nickel diphosphine complexes for LLDPE synthesis via orthogonal tandem and one-pot catalysis. NewJ Chem. 2007, 31, 502-505. [Pg.859]

New nickel-benzyne complexes (143-147) have been prepared by reaction of o-dihaloarenes with Ni(COD)2 in the presence of a trialkylphosphine followed by reduction of the oxidative addition product with either Li or 1% Na/Hg in ether [e.g., Eq. (23)]. The oxidative addition reaction depends on the nature of substituents on the arene and fails to occur when strong electron-donating groups are present. Based on NMR and mass spectrometry (MS) data, the new complexes were formulated as monomeric. It had been... [Pg.169]

Bis(trichlorosilyl)nickel(II) complex 4, having an r/ -arene hgand,is prepared by reaction of hexachloro disilane with highly reactive, vaporized nickel in the presence of toluene (Eq. 2) [12]. Worthy of note is that the arene ligand is displaced by three molecules of carbon monoxide to give 5 [13]. [Pg.133]

Because of the extraordinary strength of the carbon-fluorine bond, transition metal-mediated activation of fluoroalkanes and arenes is not easy to achieve. Nevertheless, activation of the C-F bond in highly electron-deficient compounds such as 2,4,6-trifluoropyrimidine, pentafluoropyridine, or hexafluorobenzene is possible with stoichiometric amounts of bis(triethylphosphano) nickel(O) [101] (Scheme 2.45). More recently Herrmann and coworkers [102] have described a variant of the Kumada-Corriu cross-coupling reaction [103] between fluorobenzene and aryl Grignard compounds which uses catalytic amounts of nickel carbene complexes. Hammett analysis of the relative kinetic rate constants indicated that the reaction proceeds via initial oxidative addition of the fluoroaromatic reactant to the nickel(O) species. [Pg.53]

It has been indicated by Stgpieh et al.P who studied weak intramolecular metal-arene interactions in cadmium(II) and nickel(II) complexes of benzipor-phyrins, that for weak interactions the parameters 6h, Jhc and Jhm are not necessarily correlated. According to their opinion, the changes of the magnitude of Jhc seem to be a more reliable probe for the agostic interaction than the variations of the chemical shift. [Pg.167]

DFT calculations indicate that the oxidative addition reactions of a G-F bond in GeFe at Ni(H2PGH2GH2PH2) and Pt(H2PGH2GH2PH2) proceed initially via exothermic formation of an 77 -arene complex. The G-F oxidative addition reaction is more exothermic at nickel than at platinum. The barrier for exothermic oxidative addition is higher at Pt than at Ni because of strong d-p repulsions in the transition state. Similar repulsive interactions lead to a relatively long Pt-F bond with a considerably lower stretching frequency in the oxidative addition product than for... [Pg.743]

Two recent computational studies have examined the mechanism of crosscouplings involving aryl acetates, earbamates, and sulfamates. In a study of synthetic advances with aryl pivalates, oxidative addition of Ni(0) to the aryl acetate was found to proceed by a three-centered mechanism via an T arene complex. Alternatively, in a separate study, oxidative addition involving aryl carbamates and sulfamates was found to proceed by a five-centered transition state, with coordination of the carbonyl oxygen to nickel being a key interaction in the oxidative addition. ... [Pg.338]

Recently, Eisenstein and Perutz [40] explored computationally the functionalization of electron-deficient arenes by nickel phosphine complexes. They based the study on the experimental observation of the reaction by Nakao and coworkers [41], Experimentally, either the C—H or C—F bond activated products could be observed however, the authors only proposed a mechanism where the C—H activated product was obtained via an oxidative addition mechanism (see scheme on the left on Fig. 25.31). The aim of Eisenstein and Perutz was to explore both possibilities, C—H or C—F bond activation mechanisms, as previously they demonstrated that the C—FI oxidative addition could compete with the C—F oxidative addition [42]. [Pg.733]

Nickel dimethyl complexes NiMe2(PRs)2 decompose readily in solution, either thermally or photochemically, providing an efficient method for the generation of Ni(0) complexes. The complex NiMe2(dtbpe) undergoes reductive elimination in benzene at 50-60 °C, giving rise to a binuclear Ni(0) 7r-arene complex. Careful thermolysis in THF-/ 8 over several days at 20 °G affords a 1 2 1 mixture of the ethylene complex 159, the hydride 160, and ethane (Scheme 47). If the reaction is carried out in the presence of ethylene, equimolecular amounts of 159 and ethane are formed. These results can be explained by assuming that the decomposition process involves the formation of a complex. In contrast with this behavior, the bis(carbene) dimethyl complex 45 decomposes... [Pg.83]

It is interesting to point out the relationship between the structure of compound 306 and that of other 7r-arene complexes of Pd and Pt involved in M-G bond formation or cleavage processes." " " " The ability of macrocyclic ligands to stabilize previously undetected nickel 7r-arene reactive complexes is further evidenced by the isolation and characterization of compound 308, which readily undergoes cr-Ni-C bond formation to give 309 (Equation (120))." ... [Pg.124]

Although TT-arene complexes of nickel are still relatively rare, an increasing number of such compounds featuring a variety of Ni-arene interactions have been reported. Of these, most Ni(0) compounds are prepared by the generation of an unsaturated Ni(0) species in the presence of aromatic solvents. Given the relative electron richness of Ni(0), the Ni-arene interaction in most of these complexes is rf or rf, and rarely rf exceptions are benzene)( -Bu 2 PCH2CH2PBu 2) vide infra). [Pg.186]


See other pages where Nickel complexes arene is mentioned: [Pg.91]    [Pg.148]    [Pg.323]    [Pg.109]    [Pg.615]    [Pg.419]    [Pg.105]    [Pg.108]    [Pg.452]    [Pg.248]    [Pg.4434]    [Pg.917]    [Pg.148]    [Pg.93]    [Pg.419]    [Pg.4433]    [Pg.351]    [Pg.52]    [Pg.275]    [Pg.365]    [Pg.16]    [Pg.261]    [Pg.52]    [Pg.236]    [Pg.1020]    [Pg.402]    [Pg.230]    [Pg.107]    [Pg.101]   
See also in sourсe #XX -- [ Pg.145 , Pg.146 ]

See also in sourсe #XX -- [ Pg.145 , Pg.146 ]

See also in sourсe #XX -- [ Pg.66 , Pg.117 , Pg.118 , Pg.119 ]




SEARCH



Arene complexe

Arene complexes

Arenes complexes

Metal-arene complexes nickel

© 2024 chempedia.info