萘啶雙羧酸根配體之過渡金屬錯合物的合成與催化探討

Abstract

雙核金屬催化劑被證明於催化系統中存在特殊活性，過去文獻中已有許多例子說明兩個金屬離子於催化過程中的協同效應。多牙配體的設計直接影響到金屬之配位環境與離子間距，這些性質同時也決定協同效應發生的機會，因此製備能裝載多金屬離子之多牙配基成為火紅的研究題材。 在本篇論文中，利用1, 8-萘啶- 2, 7-雙羧酸根配體(1,8-naphthyridine-2,7-dicarboxylate)做為多牙配基，且將其與銅、鈷與釕金屬配位形成錯合物Cu2(I, I)、[Co2(II, II)]2 與Ca[Ru2(II, II)]2，鑑定其晶體結構並討論其性質。萘啶羧酸根配基兩側之氮氧配體分別與三種金屬離子 形成兩組金屬五元環，多價負離子型配體除了與金屬配位能力良好外，還可穩定高價態金屬中心，且也因羧酸根與質子性分子之氫鍵作用力，使此系列錯合物可溶解於水、甲醇和乙醇等質子極性溶劑。 烯基氧化裂解反應於化學工業上多使用臭氧化反應進行，但化學家仍不斷找尋更環保且高效之替代方案，而釕金屬催化系統正活躍於該舞台。於過去文獻中，釕金屬催化之烯基氧化裂解反應常選用有機溶劑與水的共溶劑系統，本研究使用雙核釕金屬催化劑Ca[Ru2(II, II)]2 於水中進行此催化，發現其反應性十分良好，動力學曲線分析也說明雙核結構的確對烯基氧化裂解反應有助益。

Dimetallic complexes are known to have unique properties in transition metal catalyzed reactions, and there are a lot of examples proving the cooperation between metals during the catalysis. Therefore, there is a need to design and synthesis of multi-dentate ligands for construction of dimetallic systems. In this research, 1,8-naphthyridine-2,7-dicarboxylate was used as the multi-dentate ligand for complexation with ruthenium, copper and cobalt ions to form Cu2(I, I), [Co2(II, II)]2 and Ca[Ru2(II, II)]2. Moreover, we successfully disclosed their absolute structures by crystals. Naphthyridine dicarboxylate ligand can capture two metal ions to form two five-member rings with N and O donors. Such a dicarboxylate ligand not only has strong coordinating ability but also stabilizes metal centers with high oxidation state. Because of the H-bonding interaction between carboxylate groups and protic molecules, the ligand readily assists the solubility of the resulting complexes in protic solvents like water, methanol and ethanol. Industrial application on oxidative cleavage of olefins usually go through ozonolysis. However, chemists are still looking for environmental-friendly alternatives with higher efficiency. In the past, ruthenium-catalyzed oxidative cleavage reaction usually works in water-organic co-solvent system. Surprisingly, Ca[Ru2(II, II)]2 can catalyzed this reaction in water with great performance. Kinetic experiment also suggests that binuclear structure really assists the cleavage reaction.