15628-25-8Relevant articles and documents
Effect of the Bite Angle of Diphosphine Ligands on Activity and Selectivity in the Nickel-catalysed Hydrocyanation of Styrene
Kranenburg, Mirko,Kamer, Paul C. J.,Leeuwen, Piet W. N. M. van,Vogt, Dieter,Keim, Wilhelm
, p. 2177 - 2178 (1995)
The application of diphosphines with large bite angles (βn = 101-109 deg) in nickel catalysts leads to successful, regioselective hydrocyanation of styrene.
Cundy, C. S.
, p. 305 - 310 (1974)
Synergy between Experimental and Computational Chemistry Reveals the Mechanism of Decomposition of Nickel-Ketene Complexes
Staudaher, Nicholas D.,Arif, Atta M.,Louie, Janis
supporting information, p. 14083 - 14091 (2016/11/06)
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.
Fundamental studies and development of nickel-catalyzed trifluoromethylthiolation of aryl chlorides: Active catalytic species and key roles of ligand and traceless MeCN additive revealed
Yin, Guoyin,Kalvet, Indrek,Englert, Ulli,Schoenebeck, Franziska
, p. 4164 - 4172 (2015/04/14)
A catalytic protocol to convert aryl and heteroaryl chlorides to the corresponding trifluoromethyl sulfides is reported herein. It relies on a relatively inexpensive Ni(cod)2/dppf (cod = 1,5-cyclooctadiene; dppf = 1,1′-bis(diphenylphosphino)ferrocene) catalyst system and the readily accessible coupling reagent (Me4N)SCF3. Our computational and experimental mechanistic data are consistent with a Ni(0)/Ni(II) cycle and inconsistent with Ni(I) as the reactive species. The relevant intermediates were prepared, characterized by X-ray crystallography, and tested for their catalytic competence. This revealed that a monomeric tricoordinate Ni(I) complex is favored for dppf and Cl whose role was unambiguously assigned as being an off-cycle catalyst deactivation product. Only bidentate ligands with wide bite angles (e.g., dppf) are effective. These bulky ligands render the catalyst resting state as [(P-P)Ni(cod)]. The latter is more reactive than Ni(P-P)2, which was found to be the resting state for ligands with smaller bite angles and suffers from an initial high-energy dissociation of one ligand prior to oxidative addition, rendering the system unreactive. The key to effective catalysis is hence the presence of a labile auxiliary ligand in the catalyst resting state. For more challenging substrates, high conversions were achieved via the employment of MeCN as a traceless additive. Mechanistic data suggest that its beneficial role lies in decreasing the energetic span, therefore accelerating product formation. Finally, the methodology has been applied to synthetic targets of pharmaceutical relevance.
Nickelacyclic carboxylates derived from 3-hexyne and CO2 and their application in the synthesis of a new muconic acid derivative
Langer, Jens,Goerls, Helmar,Walther, Dirk
, p. 60 - 67 (2012/03/13)
The mononuclear unsaturated nickelalactones [Ni{C(Et)C(Et)-COO}(DBU) 2] (1) and [Ni{C(Et)C(Et)-COO}(dcpe)] (2) were synthesized by oxidative coupling of CO2 and 3-hexyne at zero-valent nickel in presence of DBU or dpce, respectively.
