Studies of Carbon-Carbon Bond Formation Reactions Based on Ni(II) and Pd(II) Catalysts Bearing Nitrogen-Containing Hetero-functional Bidentate Ligands
Date Issued
2007
Date
2007
Author(s)
Guan, Shih-Hau
DOI
en-US
Abstract
In this thesis, carbon-carbon bond formations are studied through three kinds of reactions: styrene polymerization, cross-couplings and nucleophilic additions.
A new series of Ni(II) complexes [(N,N')NiBr2] bearing bidentate amino-oxazoline ligands have been synthesized and applied for polymerization of styrene. With cocatalyst, MAO, these Ni(II) complexes 4 are highly efficient catalysts for styrene polymerization with activities up to ~107 g / mol [Ni] × h under optimized conditions, which possess the best performance among the catalytic Ni systems now. Effects of the structures of catalysts and the reaction parameters on the activities and characteristic properties for the polymers have been discussed here. From the 13C NMR data, the degree of stereoregularity of the synthesized polystyrene could be moderately controlled by the chiral center in the oxazoline ring although atactic polymers were generally obtained by these Ni(II) catalysts.
The neutral Pd(II) complexes [(N,N')PdCH3Cl] 5 and the cationic complexes [(N,N')PdCH3L]+ 7 were prepared for studying the mechanism for polymerization. For the neutral Pd complexes, their coordination chemistry, dynamic behavior, geometric isomerization, and reactivity toward alkynes have been studied herein. Furthermore, reactions of cationic Pd complexes with styrene, which led to the η3-π-benzyl Pd(II) complexes, made the possible mechanism of the polymerization of styrene for the Ni(II) system.
Neutral Pd(II) complexes were synthesized and involved nitrogen-containing ligands, such as mono-oxazolines, amino-oxazolines and pyridyl-pyrazoles. Among them, the chloromethylpalladium(II) complex with bidentate pyridyl-pyrazole ligands exhibited excellent activities toward Heck coupling reactions with high TONs up to 95,000,000, comparable to the palladacycle systems. In addition, the pyridyl-azolate ligands are good candidates for catalytic Suzuki-Miyaura cross-coupling reactions. In the presence of Pd(OAc)2, KF as base, and such ligands in EtOH, the couplings of aryl bromides with phenylboronic acids could proceed with high conversions at room temperature in the air. Under the same conditions, it could slowly couple aryl chloride with phenylboronic acids, which is rare for Pd catalysts with bidentate nitrogen donor ligands.
Finally, we synthesized a series of cationic allylpalladium(II) complexes bearing asymmetric amino-oxazoline ligands. The isomer interconversion is demonstrated by NOESY spectra to show a syn-syn, anti-anti exchange. Nucleophilic attacks to the Pd complexes would result in the linear and branched products. The regioselectivity is strongly dependent on the steric/electronic properties of the nucleophiles and the polarity of the used solvents.
Subjects
碳-碳鍵形成
苯乙烯聚合反應
Heck反應
Suzuki反應
胺基-噁唑啉
C-C bond formation
styrene polymerization
Heck reaction
Suzuki coupling
amino-oxazoline
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-96-D91223015-1.pdf
Size
23.31 KB
Format
Adobe PDF
Checksum
(MD5):8b0c1f8185c067880c46ae4251ec42f7