18433-72-2Relevant articles and documents
A Bimetallic Nickel-Gallium Complex Catalyzes CO2 Hydrogenation via the Intermediacy of an Anionic d10 Nickel Hydride
Cammarota, Ryan C.,Vollmer, Matthew V.,Xie, Jing,Ye, Jingyun,Linehan, John C.,Burgess, Samantha A.,Appel, Aaron M.,Gagliardi, Laura,Lu, Connie C.
, p. 14244 - 14250 (2017)
Large-scale CO2 hydrogenation could offer a renewable stream of industrially important C1 chemicals while reducing CO2 emissions. Critical to this opportunity is the requirement for inexpensive catalysts based on earth-abundant metals instead of precious metals. We report a nickel-gallium complex featuring a Ni(0)→ Ga(III) bond that shows remarkable catalytic activity for hydrogenating CO2 to formate at ambient temperature (3150 turnovers, turnover frequency = 9700 h-1), compared with prior homogeneous Ni-centered catalysts. The Lewis acidic Ga(III) ion plays a pivotal role in stabilizing catalytic intermediates, including a rare anionic d10 Ni hydride. Structural and in situ characterization of this reactive intermediate support a terminal Ni-H moiety, for which the thermodynamic hydride donor strength rivals those of precious metal hydrides. Collectively, our experimental and computational results demonstrate that modulating a transition metal center via a direct interaction with a Lewis acidic support can be a powerful strategy for promoting new reactivity paradigms in base-metal catalysis.
Cobalt-Catalyzed Asymmetric Hydroboration/Cyclization of 1,6-Enynes with Pinacolborane
Yu, Songjie,Wu, Caizhi,Ge, Shaozhong
supporting information, p. 6526 - 6529 (2017/05/29)
We report a cobalt-catalyzed asymmetric hydroboration/cyclization of 1,6-enynes with catalysts generated from Co(acac)2 and chiral bisphosphine ligands and activated in situ by reaction with pinacolborane (HBpin). A variety of oxygen-, nitrogen
Reactions of cobalt(II) with NaBH4 in the presence of bidentate phosphines: Crystal and molecular structures of CoH[Ph2P(CH2)3PPh2] 2·C6H6 and [Co(BH4)[Ph2P(CH2)5PPh 2]]20.5C6H6
Holah, David G.,Hughes, Alan N.,Maciaszek, Stanislaw,Magnuson, Vincent R.,Parker, Kenneth O.
, p. 3956 - 3962 (2008/10/08)
The reactions between Co(II) and NaBH4 in the presence of the phosphines Ph2P(CH2)nPPh2 (n = 2-6) and cis- and trans-Ph2PCH=CHPPh2 lead, through a series of intermediates, to the formation of CoH(phosphine)2 species, except in the case of the trans ligand, where hydrogenation occurs and CoH[Ph2P(CH2)2PPh2]2 is formed. Single-crystal X-ray diffraction studies on CoH[Ph2P(CH2)3PPh2] 2·C6H6 show that the compound crystallizes in the monoclinic space group P21/n, with unit cell parameters a = 13.640 (6) A?, b = 15.794 (5) A?, c = 23.870 (9) A?, β = 101.04 (4)°, V = 5047.2 A?3, Z = 4, and dcalcd = 1.267 g cm-3. The structure converged to a conventional R factor of 0.042 for 4754 observations and showed a five-coordinated Co(I) atom with two chelating phosphines and a hydride group in a distorted-trigonal-bipyramidal arrangement. In addition, with two of the longer chain phosphines (n = 4, 5) it is possible to isolate Co(I)-BH4 species shown, in the case of n = 5, to be [Co-(BH4)[Ph2P(CH2)5PPh 2]]2·0.5C6H6. This compound crystallizes in the triclinic space group P1 with unit cell parameters a = 10.305 (3) A?, b = 14.990 (3) A?, c = 20.343 (5) A?, α = 107.87 (2)°, β = 90.72 (2)°, γ = 105.88 (2)°, V = 2861 (3) A?3, Z = 2, and dcalcd = 1.240 g cm-3. The structure converged to a conventional R factor of 0.052 for 4290 observations. The dimeric species consists of two Co(I) atoms bridged by both phosphine ligands and BH4 ligands in a hitherto unknown way such that each BH4 group chelates to each cobalt using one common hydrogen, leaving one terminal hydrogen uninvolved. Alternatively, the BH4 group can be considered as a tridentate ligand to two cobalt atoms separated by 2.869 (1)A?. The cobalt and boron atoms are almost coplanar, but, since there is no obvious strain in the Co-P(CH2)5P-Co linkages, the steric and electronic requirements of the bridging tetrahydroborate groups apparently dictate the distorted coordination geometry about the Co atoms.
