帶有苯腙基團的吡唑配位基的雙鎳(II)及雙鈷(II)金屬錯合物的合成與鑑定

Synthesis and Characterizations of Dinuclear Nickel(II) and Cobalt(II) Complexes with Bridging Pyrazole Ligand Bearing Appended Phenylhydrazone Groups

劉彥辰(Yen-Chen Liu)

指導教授 ： 張慕傑

國立臺灣大學/理學院/化學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202101741

摘要

Pyrazole在有機化學中常擔任多功能積木的角色，近年之相關研究已開發出具有雙功能的pyrazole衍生物，並以此為出發點合成出不同的配位基。故本篇欲設計以pyrazole為中心架構，以phenyl- hydrazone 為側臂，建構具有氧化還原活性(redox active)與pendent-proton relay特性之配位基，結合此兩種金屬-配位基協同(Metal-Ligand Cooperation)作用於錯合物中，並融入金屬-金屬協同作用(Metal-Metal Cooperation)，有望在催化循環中穩定金屬不常見的氧化態，並解決電子與質子轉移的問題。
將配位基與不同當量數的鹼反應以進行拔氫反應測試，藉此形成帶有不同電荷的拔氫配位基，將這些拔氫配位基與金屬起始物NiCl2(dme)或CoCl2進行錯合物合成反應，分別合成出雙鎳(3與5)和雙鈷(6)金屬錯合物，而在錯合物拔氫反應測試中發現，雙鎳錯合物3可藉由與t-BuOK反應以形成另一種配位模式的雙鎳錯合物4。而由帶有不同電荷的拔氫配位基所合成的雙鎳錯合物3、4、5，經由晶體結構發現 ，隨著配位基上被拔除的氫離子數量增加，兩個鎳金屬中心的距離也隨之增加(3: 2.904(1) Å→ 5: 3.381(1) Å→ 4: 3.768(7) Å)。此外，經由循環伏安法來測試錯合物4及6的氧化還原性質，發現此兩種錯合物具有相似的氧化還原性質，均具有兩組可逆的氧化峰與一組不可逆的氧化峰，而在理論計算幫助下，認為錯合物4及6在循環伏安法上的可逆氧化峰皆為配位基為主的氧化反應，也展現此兩種錯合物能於催化反應中協助多電子轉移的潛能。

關鍵字

金屬-金屬協同作用 ； 金屬-配位基協同作用 ； pendant proton relay ； ligand-based oxidation ； 雙金屬多功能錯合物 ； 具氧化還原活性之配位基

並列摘要

Pyrazole are considered as the building blocks in organic chemistry. In recent years, related research has developed difunctional pyrazole derivatives, and used this as a starting point to synthesize different ligands. Therefore, this article intends to design a complex with pyrazole as the backbone and phenylhydrazone as the side arm to construct a ligand with redox active and pendent-proton relay characteristics. Combining these two synergistic effects in the complex and incorporating metal-metal cooperation are expected to stabilize the uncommon oxidation state of metals in the catalytic cycle and solve the problem of electron and proton transfer.
The ligands are reacted with different equivalents of base to perform the deprotonation test to form different charges of deprotonated ligand. Then the following metalations were done by reacting the deprotonated ligand with NiCl2(dme) and CoCl2 to synthesize di-nickel and di-cobalt complexes 3, 5, and 6 respectively. The di-nickel complex 4 was obtained from the deprotonation reaction of 3. Besides, as negative charges of the deprotonated ligand increase (3: LH2-→ 5: LH2-→ 4: L3-), the bond distance between two nickel centers also increases (3: 2.904(1) Å→ 5: 3.381(1) Å→ 4: 3.768(7) Å). In addition, the redox properties of complexes 4 and 6 were tested by cyclic voltammetry, and it was found that these two complexes have similar redox properties, With the help of theoretical calculations, it is believed that the reversible oxidation peaks of complexes 4 and 6 are ligand-based oxidation reactions, which also shows that these two complexes can assist multi-electron transfer in catalytic reactions and has the potential to activate small molecules.

並列關鍵字

metal-metal cooperation ； metal-ligand cooperation ； redox-active ligand ； pendant proton relay ； multifunctional bimetallic complex ； ligand-based oxidation

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