| Summary: | 博士 === 國立臺灣大學 === 化學研究所 === 104 === In this thesis, we have prepared a series of 1,9,10-anthyridine-based multidentate ligands (5a~5k), coordinating with various transition metal ions including Pd, Rh, Cu, Ni, which could be applied in many catalytic reactions.
Coordination of 5a, 5b with Pd(OAc)2 yielded the cyclopalladated complexes [(5a)PdBr(H2O)] (6a), [(5b)2Pd2(OAc)2] (6b). Treatment of 6a, 6b with PPh3 resulted in the formation of stable dimer cyclopalladated complexes {[(5a)2Pd2(PPh3)2]Br2} (7a), {[(5b)2Pd2(PPh3)2] } (7b), which was capable to be converted to the original ones by using sulfur or gold (I) complex to break the Pd-C bond. X-ray structural cha- racterization showed that the Pd-N bond trans to the carbon atom was longer than the other one due to the trans-influence. The use of cyclopalladated complexes in cataly- sis has been increased significantly because of their strong σ-donor nature. It exhibit- ed good catalytic activities on the catalysis of Suzuki-Miyaura coupling of chloro- arenes with phenylboronic acid in protic solvents like water. Besides, it was able to catalyze carbon boron bond cross coupling with excellent yields and functional group tolerance.
In the second part of this research, reaction of (5a,5c,5d,5e) with Rh2(OAc)4 provided the cyclometalated complexes [Rh2(OAc)3(metalated-5a, 5c, 5d, 5e)] (8a, 8c, 8d, 8e), and the existence of Rh-C bond in axial position could be confirmed by 1H- NMR, 13C-NMR and X-ray crystallography. Under acidic conditions, cleavage of the Rh–C bond in 8e took place to give the corresponding coordination complex- es [Rh2(OAc)3(5e)][PF6] (9e). Treatment of 8d, 8e with PPh3 led to the phosphine- cyclometalated species {Rh2(OAc)2[(C6H4)PPh2](metalated-5d, 5e)} (10d, 10e). X- ray structural determinations revealed that two Rh-C bond distances were quite close to each other, which meaned trans influence from the dirhodium metal-metal bond was not so signi- ficant. However, due to the trans influence, Rh-O bond trans to the carbon atom would longer than the one trans to the phosphorous atom. In the catalytic application, all the cyclorhodated complexes, especially 8e, showed the activity on allylic oxidation to α, β unsaturated carbonyl compounds with outstanding reactivity, regioselectivity and functional group tolerance.
Biomimetic bimetallic complexes have been proved to have unique reactivity in specific catalytic system, and widely regarded as the cooperation between metals dur- ing the catalytic reaction. In the third part of this thesis, we have synthesized dimetal complexes [(5f)Cu2(ACN)2(H2O)4][ClO4]4 (11f), [(5g)Cu2(ClO4)2][PF6]2 (11g), [(5f)- Ni2(OTFA)2-(H2O)6][OTFA]2 (14f), [(5g)Ni2(OTFA)4(H2O)] (14g) through complexa- tion of 5f, 5g with Cu(ClO4)2, Ni(OAc)2, and all of the dimetal complexes were determined by single crystal X-ray diffraction. By means of UV-vis and infrared spec- troscopy, the coordination geometry could be further confirmed. Electrochemistry analysis showed that both of dicopper complexes had two reduction potential and one oxidation potential, however, strong π-acceptor nature of terpyridine ligand could stabilize the low-valent central metal, and lower the highest occupied molecular orbi- tal, which might explain why 11g had high oxidation potential.
The dicopper complex 11g acted as an effective catalyst toward many kinds of oxidation reactions, such as benzyl alcohol could be selective oxidize to benzyl ben- zoate. Without our designed ligand, the desired esters product weren’t available. It’s worth mentioning that part of the alkyl mono or di-ol could work as well. Furthermore, by means of kinetic experiments and ESI-MASS analysis could confirm our proposed mechanism. The dinickel complex 14g could catalyze not only aryl, but alkyl acid reduction to alcohol with good chemoselectivity. Confirmed by the intermediate’s crystal structure, which indicated that 14g could activate acid through bridging mode, followed by hydrosilylation.
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