23884-11-9Relevant articles and documents
Mechanistic insights into dehydrocoupling of amine boranes using dinuclear zirconocene complexes
Al Hamwi, Hanan,Beweries, Torsten,Drexler, Hans-Joachim,Heller, Detlef,Jannsen, Nora,Lindenau, Kevin,Neymeyr, Klaus,Rei?, Fabian,Rippke, Mirko,Sawall, Mathias,Selle, Carmen,Spannenberg, Anke
supporting information, p. 4034 - 4050 (2021/07/06)
Catalytic dehydrocoupling of H3B·NMe2H using the in situ system Cp2Zr(Cl)(μ-Me3SiC3SiMe3)Zr(Cl)Cp2 (1)/MeLi was studied as a model for previously reported dehydropolymerisation of H3B·NMeH2. NMR and UV-vis spectroscopic monitoring of the precatalyst activation sequence as well as a series of stoichiometric experiments showed that formation of a zirconocene dimethyl complex (2) is not relevant for activation of the precatalyst. Instead, deprotonation of H3B·NMe2H and reaction of thus formed Li[NMe2BH3] is proposed to result in the formation of Zr amidoborane and hydride species. DFT analysis using such complexes as active species showed a pathway for formation of H2 and H2BNMe2. 1H NMR spectroscopic monitoring and stoichiometric control experiments revealed the formation of unusual diamagnetic dinuclear complexes Cp2Zr(C2SiMe3)(μ-R)ZrCp2 (R = CH2SiMe3, 7; R = H, 9) formed by activation of the allenediide unit of the precatalyst 1. Such species can be regarded as rare single-component catalysts for the dehydrocoupling of amine boranes. This journal is
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
