23884-11-9Relevant articles and documents
Metal-ligand cooperative κ1-N-pyrazolate Cp*RhIII-catalysts for dehydrogenation of dimethylamine-borane at room temperature
Iwasaki, Takanori,Nozaki, Kyoko,Pal, Shrinwantu
supporting information, p. 7938 - 7943 (2021/06/21)
3,5-Dimethylpyrazole (Pz*H) in well-defined Cp*RhIII(Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) complexes, or as an additive to [Cp*RhCl2]2enhances catalytic activity in the dehydrogenation of dimethylamine-borane (DMAB) at room-temperature. Mechanistic studies indicate that the Lewis acidic RhIII-centre and dangling N-atom of the Pz* fragment operate cooperatively in accepting a hydride and proton from DMAB, respectively, leading directly to dimethylamino-borane and a RhIII-H complex. The rate limiting step involves protonation of the RhIII-H by the proximal NH fragment of the Pz*H moiety.
Impact of the novel Z-acceptor ligand bis{(ortho-diphenylphosphino)phenyl}zinc (ZnPhos) on the formation and reactivity of low-coordinate Ru(0) centers
Beck, Madeleine L.,Burnage, Arron L.,Farmer, James C. B.,Isaac, Connie J.,Macgregor, Stuart A.,Mahon, Mary F.,Miloserdov, Fedor M.,Whittlesey, Michael K.
, p. 15606 - 15619 (2020/11/20)
The preparation and reactivity with H2 of two Ru complexes of the novel ZnPhos ligand (ZnPhos = Zn(o-C6H4PPh2)2) are described. Ru(ZnPhos)(CO)3 (2) and Ru(ZnPhos)(IMe4)2 (4; IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) are formed directly from the reaction of Ru(PPh3)(C6H4PPh2)2(ZnMe)2 (1) or Ru(PPh3)3HCl/LiCH2TMS/ZnMe2 with CO and IMe4, respectively. Structural and electronic structure analyses characterize both 2 and 4 as Ru(0) species in which Ru donates to the Z-type Zn center of the ZnPhos ligand; in 2, Ru adopts an octahedral coordination, while 4 displays square-pyramidal coordination with Zn in the axial position. Under photolytic conditions, 2 loses CO to give Ru(ZnPhos)(CO)2 that then adds H2 over the Ru-Zn bond to form Ru(ZnPhos)(CO)2(μ-H)2 (3). In contrast, 4 reacts directly with H2 to set up an equilibrium with Ru(ZnPhos)(IMe4)2H2 (5), the product of oxidative addition at the Ru center. DFT calculations rationalize these different outcomes in terms of the energies of the square-pyramidal Ru(ZnPhos)L2 intermediates in which Zn sits in a basal site: for L = CO, this is readily accessed and allows H2 to add across the Ru-Zn bond, but for L = IMe4, this species is kinetically inaccessible and reaction can only occur at the Ru center. This difference is related to the strong π-acceptor ability of CO compared to IMe4. Steric effects associated with the larger IMe4 ligands are not significant. Species 4 can be considered as a Ru(0)L4 species that is stabilized by the Ru→Zn interaction. As such, it is a rare example of a stable Ru(0)L4 species devoid of strong π-acceptor ligands.
Catalysis and Mechanism of H2 Release from Amine-Boranes by Diiron Complexes
Lunsford, Allen M.,Blank, Jan H.,Moncho, Salvador,Haas, Steven C.,Muhammad, Sohail,Brothers, Edward N.,Darensbourg, Marcetta Y.,Bengali, Ashfaq A.
, p. 964 - 973 (2016/02/03)
Studies focused on the dehydrogenation of amine-borane by diiron complexes that serve as well-characterized rudimentary models of the diiron subsite in [FeFe]-hydrogenase are reported. Complexes of formulation (μ-SCH2XCH2S)[Fe(CO)su
