Browsing by Author "Liu, Hsueh-Ju"

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Linear, mixed-valent homocatenated tri-tin complexes featuring Sn-Sn bonds
(2020-06-25)
Chang, Wei-Chieh
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Raj, Ankit
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Hiramatsu, Hirotsugu
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Li, Han-Jung
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Ziegler, Micah S.
A series of tri-tin complexes((LSn)-Sn-Ph)(3)Xwith triple-decker structures (L-Ph= 2,5-di(o-pyridyl)-3,4-diphenylpyrrolate; X = Cl, AlCl4, OTf, and PF6) was synthesized by reducingL(Ph)SnClwith (LiBBu3H)-Bu-s and subsequent reactions. Structural characterization of((LSn)-Sn-Ph)(3)Clrevealed a Sn-Sn-Sn core, and DFT calculations suggest that its HOMO is primarily sigma-bonding along the tri-tin framework.((LSn)-Sn-Ph)(3)Clreacts with W(CO)(5)THF to afford((LSn)-Sn-Ph)(2)(W(CO)(5))(2)andL(Ph)SnCl, implying that((LSn)-Sn-Ph)(3)Clmay exhibit dynamic behavior in solution.
Silica-Supported Cu Nanoparticle Catalysts for Alkyne Semihydrogenation: Effect of Ligands on Rates and Selectivity
(2016-12-21)
Fedorov, Alexey
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Liu, Hsueh-Ju
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Lo, Hung-Kun
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Coperet, Christophe
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應用化學系
Narrowly dispersed, silica-supported Cu nano particles (ca. 2 nm) prepared via surface organometallic chemistry from a mesityl complex [Cu(5)Mes(5)] are highly active for the hydrogenation of a broad range of alkynes. High-throughput experimentation allows for identifying the optimal ligand and reaction conditions to turn these supported Cu nanoparticles into highly chemo- and stereoselective catalysts for the preparation of Z-olefins (overall, 23 examples). For instance, PCy3-modified Cu nanoparticles semihydrogenate 1-phenyl-l-propyne to cis-beta-methylstyrene (20 bar H-2, 40 degrees C) with turnover number and turnover frequency of ca. 540 and 1.9 min(-1), respectively, and with 94% selectivity at full conversion.
Synthesis, structures, and reactivity studies of cyclometalated N-heterocyclic carbene complexes of ruthenium
(2018-09-21)
Liu, Hsueh-Ju
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Ziegler, Micah S.
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Tilley, T. Don
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應用化學系
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Department of Applied Chemistry
An unusual cyclometalation reaction results from a C-C bond activation in Cp*(IPr)RuCl to give Cp*(IPr)Ru(L) featuring a NHC-C(sp(2)) chelating ligand (5-L; L = propene, N-2; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene; IPr = 1-(6-isopropylphenyl)-3-(2,6-diisopropylphenyl)imidazol-2-ylidene). DFT calculations were employed to elucidate the C-C bond activation pathway. Reactions of cyclometalated ruthenium complexes bearing NHC-C(sp(2)) and NHC-C(sp(3)) ligands (5-L and Cp*(IXy-H)Ru(N-2), 1a, respectively where IXy = 1,3-bis(2,6-dimethylphenyl)-imidazol-2-ylidene; IXy-H is the deprotonated form of (IXy)) are reported. Deprotonation of 1a by an equimolar mixture of benzyl potassium and 18-crown-6 afforded a doubly-cyclometalated complex [Cp*(IXy-2H)Ru][K(18-crown-6)] (7). A lower CO stretching frequency in Cp*(IXy-H)Ru(CO) (8) vs. Cp*(IPr)Ru(CO) (9) suggests that the NHC-C(sp(3)) ligand is more electron donating. Complexes 5-L reacted with H-2 to give the dihydride Cp*(IPr)RuH2 (11). In comparison, after an initial oxidative addition of H-2, complex 1a with its more reactive Ru-C(sp(3)) bond underwent C-H bond reductive elimination, and a second oxidative addition of H-2 afforded the trihydride Cp*(IXy)RuH3 (10). Reaction of 1a with B(C6F5)(3) resulted in a zwitterionic complex Cp*Ru(IXy) (12; IXy = 1-[2-((C6F5)(3)BCH2)C6H3-6-methyl]-3-(2,6-dimethylphenyl)imidazol-2-ylidene-1-yl) by the formation of a new C-B bond. In contrast, B(C6F5)(3) abstracted a hydride from 5-L and promoted a very unusual C-C bond formation involving insertion of an allyl ligand into a Ru-C bond to form [Cp*Ru(IPr)][HB(C6F5)(3)] (IPr = 1-[2-(CH2?CHCH2)C6H3-6-isopropyl]-3-(2,6-diisopropyl)imidazol-2-ylidene-1-yl) (13).