15629-93-3Relevant academic research and scientific papers
A broadly applicable strategy for entry into homogeneous nickel(0) catalysts from air-stable nickel(II) complexes
Standley, Eric A.,Smith, Stacey J.,Mueller, Peter,Jamison, Timothy F.
supporting information, p. 2012 - 2018 (2014/05/20)
A series of air-stable nickel complexes of the form L2Ni(aryl) X (L = monodentate phosphine, X = Cl, Br) and LNi(aryl)X (L = bis-phosphine) have been synthesized and are presented as a library of precatalysts suitable for a wide variety of nickel-catalyzed transformations. These complexes are easily synthesized from low-cost NiCl2·6H2O or NiBr 2·3H2O and the desired ligand followed by addition of 1 equiv of Grignard reagent. A selection of these complexes were characterized by single-crystal X-ray diffraction, and an analysis of their structural features is provided. A case study of their use as precatalysts for the nickel-catalyzed carbonyl-ene reaction is presented, showing superior reactivity in comparison to reactions using Ni(cod)2. Furthermore, as the precatalysts are all stable to air, no glovebox or inert-atmosphere techniques are required to make use of these complexes for nickel-catalyzed reactions.
One-step simple preparation of catalytic initiators for catalyst-transfer Kumada polymerization: Synthesis of defect-free polythiophenes
Chavez, Carlos A.,Choi, Jinwoo,Nesterov, Evgueni E.
, p. 506 - 516 (2014/02/14)
Externally initiated living catalyst-transfer polymerization based on Ni(II)-catalyzed Kumada coupling of aromatic halogen-substituted Grignard monomers is an established and highly efficient method for the controlled preparation of conjugated polymers such as polythiophenes and poly(p-phenylenes). In this contribution, we report a simple preparation of external catalytic initiators for such a polymerization based on oxidative addition between a readily available Ni(0) complex Ni(dppp)2 (where dppp is 1,3-bis(diphenylphosphino)propane) and various aryl halides. As a direct challenge to previous reports and established opinion that such a reaction would be impossible, this clean and efficient oxidative addition enables simple preparation of highly reactive catalytic initiators for the catalyst-transfer polymerization. In particular, we demonstrated that polymerization of 5-halo-2-thienylmagnesium monomers initiated by these catalysts produced highly regioregular, defect-free polythiophenes and block copolymers with high molecular weight and low polydispersity. We also found that the polymers prepared using this catalytic system showed a uniform end-group composition with one end terminated with an aryl group from the catalytic initiator and the other end with Br. The bromine termination could potentially allow further synthetic manipulations with the polymers. Overall, this convenient and advantageous method for the preparation of external catalytic initiators provides a simple and straightforward approach to controlled synthesis of polythiophenes and other conjugated polymers.
Homogeneous hydrogenation and isomerization of 1-octene catalyzed by nickel(II) complexes with bidentate diarylphosphane ligands
Mooibroek, Tiddo J.,Wenker, Erica C. M.,Smit, Wietse,Mutikainen, Ilpo,Lutz, Martin,Bouwman, Elisabeth
, p. 8190 - 8201 (2013/08/23)
A systematic library of 24 nickel(II) complexes with bidentate diphosphane ligands was synthesized, and the solid-state structures of five of them were determined with X-ray crystallography. The compounds C1-C3 are common P 2NiIIX2-type complexes, while C4 contains a unique [P2NiII(NH3)(OAc)]+ square-planar structure with a P2NO donor set and C5 constitutes a rare [(P2NiII)2(μ-OH)2] 2+ dinuclear compound. The catalytic activity of all complexes was tested in the hydrogenation and/or isomerization of 1-octene in a CH 2Cl2/CH3OH reaction medium. Catalyst precursors bearing ligands with o-alkoxy aryl rings selectively hydrogentate 1-octene to n-octane, while catalytic systems comprising ligands without the o-alkoxy functionality selectively isomerize the substrate to a mixture of internal alkenes, mostly cis- and trans-2-octene. The conversion is enhanced by equipping the ligand aryl rings with electron-donating alkoxy groups, by increasing the steric bulk of the backbone and/or the aryl rings, by employing relatively noncoordinating anions, and by adding a base as the cocatalyst. Using the compound [Ni(L3X)I2] as the catalyst precursor and upon application of standard hydrogenation conditions, full conversion of the substrate was achieved in 1 h to isomerization products only (TON = 1940). When a catalytic amount of the base is added, a similar result is obtained even in the absence of H2. A maximum TON of 4500 in 1 h with 96% selectivity for n-octane was achieved by employing [Ni(oMeO-L3X)(NH3)(OAc)]PF6 as the catalyst precursor.
