502159-02-6Relevant academic research and scientific papers
Synthesis and characterization of novel half-metallocene-type group IV complexes containing phosphine oxide - Phenolate chelating ligands and their application to ethylene polymerization
Liu, Jing-Yu,Liu, San-Rong,Li, Bai-Xiang,Li, Yan-Guo,Li, Yue-Sheng
body text, p. 4052 - 4059 (2011/10/03)
A series of novel half-metallocene-type group IV metal complexes containing phosphine oxide-phenolate chelating ligands of type CpMCl2[O-2R 1-4R2-6(Ph2P=O)C6H2] (Cp = C5H5, M = Ti, 2a: R1 = R2 = H; 2b: R1 = Ph, R2 = H; 2c: R1 = tBu, R2 = H; 2d: R1 = R2 = tBu; M = Zr, 3b: R1 = Ph, R2 = H; 3c: R1 = tBu, R2 = H; 3d, R1 = R2 = tBu) have been synthesized in high yields (60-76%) from CpMCl3 (M = Ti, Zr) with 1.0 equiv of 2R1-4R2-6(Ph2P=O)C 6H2OH in THF and in the presence of triethylamine, and the complexes were identified by NMR and mass spectra as well as elemental analysis. Structures for 2a-d and 3d were further confirmed by X-ray crystallography. Complexes 2a-d adopt a five-coordinate, distorted square-pyramidal geometry around the titanium center. Complex 3d has a six-coordinate, distorted octahedral geometry around the zirconium center, in which the equatorial positions are occupied by oxygen atoms of the chelating phosphine oxide-phenolate ligand and two chlorine atoms. The cyclopentadienyl ring and the oxygen atom of the THF molecule are coordinated on the axial position. When activated by modified methylaluminoxane, all complexes exhibited moderate to high activities toward ethylene polymerization, giving high molecular weight polymer with a unimodal molecular weight distribution. The substituents on ligands and the metal center as well as the reaction conditions have a profound effect on the polymerization. It should be noted that zirconium complexes 3b-d displayed notable ethylene polymerization activity even at high temperature (75 C). Moreover, using Ph3CB(C6F 5)4/i-Bu3Al in place of MMAO as a cocatalyst, 3b-d also generate high molecular weight polymer with high efficiency under the same conditions.
Ethylene polymerization by the chromium catalysts based on bidentate [O, P=O] or [S, P] ligands
He, Li-Peng,Mu, Hong-Liang,Li, Bai-Xiang,Li, Yue-Sheng
experimental part, p. 311 - 319 (2010/11/05)
Novel chromium catalysts based on bidentate phenoxy- phosphinoyl (HO-2R1-4R2-6(Ph2P=O)C6H2: R1 = R2 = H, 3a; R1 = tBu, R2 = H, 3b; R1 = R2 = tBu, 3c; R1 = R2/sub
Stereoselective Wittig olefination reactions employing a novel ortho-P-aryl alkoxide effect
McNulty, James,Keskar, Kunal
scheme or table, p. 7054 - 7057 (2009/04/07)
Non-stabilized ortho-P-alkoxy-substituted ylides react with aromatic and aliphatic aldehydes providing (E)-olefins with high stereocontrol, also allowing easy phosphine oxide removal in certain cases.
Identification of Suitable Ligands for a Transition Metal-Catalyzed Reaction: Screening of a Modular Ligand Library in the Enantioselective Hydroboration of Styrene
Blume, Florian,Zemolka, Saskia,Fey, Thorsten,Kranich, Remo,Schmalz, Hans-Guenther
, p. 868 - 883 (2007/10/03)
Based on a general modular synthetic scheme, a variety of chiral bidentate P/P-, P/S-, P/N-, and P/Se-ligands is accessible in an efficient divergent manner starting from phenol or naphthol derived backbone systems. A library of 20 selected ligands was tested in the Rh-catalyzed asymmetric hydroboration of styrene to give 1-phenylethanol in up to 91% ee after oxidative work-up. It was demonstrated that small variations of the ligand structures lead to pronounced, unpredictable differences in the performance of the in situ generated rhodium complexes. The modular approach should be applicable for the identification and optimization of suitable ligands for other transition metal-catalyzed transformations with comparably low effort.
