Browsing by Subject "3RD-ROW ATOMS"

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  • Rong, Mark K.; Holtrop, Flip; Bobylev, Eduard O.; Nieger, Martin; Ehlers, Andreas W.; Slootweg, J. Chris; Lammertsma, Koop (2021)
    Novel seven-membered cyclic imine-based 1,3-P,N ligands were obtained by capturing a Beckmann nitrilium ion intermediate generated in situ from cyclohexanone with benzotriazole, and then displacing it by a secondary phosphane under triflic acid promotion. These "cycloiminophosphanes" possess flexible non-isomerizable tetrahydroazepine rings with a high basicity; this sets them apart from previously reported iminophophanes. The donor strength of the ligands was investigated by using their P-kappa(1)- and P,N-kappa(2)-tungsten(0) carbonyl complexes, by determining the IR frequency of the trans-CO ligands. Complexes with [RhCp*Cl-2](2) demonstrated the hemilability of the ligands, giving a dynamic equilibrium of kappa(1) and kappa(2) species; treatment with AgOTf gives full conversion to the kappa(2) complex. The potential for catalysis was shown in the Ru-II-catalyzed, solvent-free hydration of benzonitrile and the Ru-II- and Ir-I-catalyzed transfer hydrogenation of cyclohexanone in isopropanol. Finally, to enable access to asymmetric catalysts, chiral cycloiminophosphanes were prepared from l-menthone, as well as their P,N-kappa(2)-Rh-III and a P-kappa(1)-Ru-II complexes.
  • Boom, Devin H. A.; de Boed, Ewoud J. J.; Nicolas, Emmanuel; Nieger, Martin; Ehlers, Andreas W.; Jupp, Andrew R.; Slootweg, J. Chris (2020)
    The reaction of the intramolecular frustrated Lewis pair (FLP) tBu2PCH2BPh2 with the amine-boranes NH3·BH3 and Me2NH·BH3 leads to the formation of the corresponding FLP-H2 adducts as well as novel five-membered heterocycles that result from capturing the in situ formed amino-borane by a second equivalent of FLP. The sterically more demanding tBu2PCH2BMes2 does not form such a five-membered heterocycle when reacted with Me2NH·BH3 and its H2 adduct liberates dihydrogen at elevated temperatures, promoting the metal-free catalytic dehydrogenation of amine-boranes.
  • Rong, Mark K.; van Duin, Koen; van Dijk, Tom; de Pater, Jeroen J. M.; Deelman, Berth-Jan; Nieger, Martin; Ehlers, A. W.; Slootweg, J. Chris; Lammertsma, Koop (2017)
    Highly stable iminophosphanes, obtained from alkylating nitriles and reaction of the resulting nitrilium ions with secondary phosphanes, were explored as tunable P-monodentate and 1,3-P,N bidentate ligands in rhodium complexes. X-ray crystal structures are reported for both k1 and k2 complexes with the counterion in one of them being an unusual anionic coordination polymer of silver triflate. The iminophosphane-based ruthenium(II)-catalyzed hydration of benzonitrile in 1,2-dimethoxyethane (180 degrees C, 3 h) and water (100 degrees C, 24 h) and under solvent free conditions (180 degrees C, 3 h) results in all cases in the selective formation of benzamide with yields of up to 96%, thereby outperforming by far the reactions in which the common 2-pyridyldiphenylphosphane is used as the 1,3-P,N ligand.