脲酶活性中心之雙鎳擬態化合物合成及其對硫醇類與a, b烯酮類未飽合鍵共軛加成催化反應之研究

Dinickel Mimics for the Active Site of Urease and Their Catalysis toward Conjugate Addition of Thiols to a,b-Unsaturated Carbonyl Compounds

曾煥升(Huan-Sheng Tseng)

指導教授 ： 李位仁

國立臺灣師範大學/理學院/化學系/博士(2008年)

摘要

本研究係以含苯咪唑或吡啶的多牙配位基合成出一系列的鎳錯合物，並利用紅外線、核磁共振、質譜、紫外光-可見光等光譜，以及X-光結構解析等方法，完成一系列鎳錯合物的鑑定。配位著雙(1-甲基苯咪唑-2-甲基)胺三牙基(L1)的鎳錯合物，其鎳金屬中心的配位環境均為八面體的幾何構形，而配位著雙(1-甲基苯咪唑-2-甲基)-10-樟腦磺醯胺配位基(L2)的鎳錯合物則可為四面體、四角錐、或八面體的幾何構形。鍵結著L1或L2配位基的鎳錯合物，其鎳金屬的核數可藉由調控苯咪唑配位基中央氮原子的配位能力來控制；同時，這些鎳錯合物的核數也會隨溫度的變化而有所不同。若鎳金屬錯合物配位著含雙取代苯甲酸根多牙基(L6、L7或L8)，則兩鎳金屬離子會與配位基的苯甲酸根形成W型的鍵結方式，同時每個鎳金屬中心均為八面體的配位環境。尿素分子可以配位至雙取代苯甲酸根錯合物的鎳金屬離子中心。由具尿素配位化合物的順磁性核磁共振氫光譜顯示，尿素分子在溶液中仍配位在鎳金屬離子上。由尿素與鎳金屬離子鍵結的事實，激勵我們以鎳錯合物對硫醇類與烯酮類a, b未飽合鍵進行共軛加成催化反應之研究。在我們的系統中得到了高產率的共軛加成產物，並發現親核基的共軛效應較誘導效應主導共軛加成產率的高低。

關鍵字

雙鎳擬態模型錯合物 ； 脲酶模型錯合物 ； 雙取代苯甲酸根多牙基

並列摘要

A series of nickel complexes supported by a benzimidazolyl or pyridinyl polydentate ligand have been synthesized and fully characterized by FT-IR, NMR, ESI-MS, UV-vis spectroscopies, and X-ray crystallography. Complexes coordinated with the tridentate bis(1-methylbenzimidazolyl-2-methyl)amine ligand exhibited an octahedral geometry at the nickel center, whereas the geometry of the complexes supported with the bis(1-methylbenzimidazolyl-2-methyl)-
10-camphorsulfonamide ligand could be tetrahedral, square pyramidal, or octahedral. The nuclearity of the nickel complexes with the tripodal ligand can be controlled by modulating the coordinating ability of the center nitrogen of the supported benzimidazolyl ligand; meanwhile, the nuclearity of those complexes is temperature dependent. If the nickel complexes coordinated by a disubstituted benzoate polydentate ligand, a W-shaped dinickel core with the carboxylate group of the benzoate ligand was formed, and each nickel center possessed an octahedral geometry. Urea molecules can coordinate to the nickel centers of the disubstituted benzoate complexes. The paramagnetic 1H-NMR spectra of the dinickel urea adducts reveal that the urea molecule remain bound in the solution. The bonding of urea inspires us to exam the conjugate addition of thiols to ,-unsaturated carbonyl compounds catalyzed by the dinickel complexes bearing solvent molecules. High yields for the conjugate additions were observed, and the yield was found to be more dominated by the conjugate effect than the inductive effect in our system.

並列關鍵字

dinickel mimics ； urease model ； disubstituted benzoate polydentate ligand

參考文獻

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