萘啶吡啶嘧啶二胺配基及其直線型六核金屬串錯合物之合成及研究

Abstract

摘要 本篇論文，以萘啶吡啶嘧啶二胺配基( H2nypmpda )為主要討論的 對象，並研究此配基的合成和用此六氮配基合成出的直線型六核金屬 串錯合物之結構和相關特性。 不對稱六氮配基H2nypmpda 的合成，是以Pd 當催化劑所進行的 反應。將H2nypmpda 和金屬鎳在高溫下，滴入t-BuOK 而能形成直線 型六核金屬串錯合物[Ni6(μ6-nypmpda)4Cl2]2+，而藉由加入還原劑N2H4 亦可成功合成出還原態的[Ni6(μ6-nypmpda)4Cl2]+錯合物。 此兩化合物在X-ray 單晶結構上大致上都相同，兩端鎳離子為五 配位的四方角錐形，中間四個鎳離子則是四配位的平面四邊形，其中 最主要的差別則是在於鍵長Ni(1)-Ni(2)和Ni(2)-N。在還原態中， Ni(1)-Ni(2) 鍵長較短，相反地Ni(2)-N 鍵長比較長，這是因為還原的 電子填入dx2-y2 軌域，而dx2-y2 軌域對Ni(1)-Ni(2)來說是鍵結軌域對 Ni(2)-N 來說則是反鍵結軌域，所以會導致這樣的結果。 在磁性上，[Ni6(μ6-nypmpda)4Cl2]2+則有反鐵磁的性質，而兩端鎳 離子的自旋偶合常數J16 = -2.89 cm-1，電化學以伏安法研究性質還原 電位發現有四對氧化還原對，分別為E(red1) 1/2 = -0.07、E(red2) 1/2 = -0.24、 E(red3) 1/2 = -0.46、E(red4) 1/2 = -0.68，研究結果証實此化合物比較容易還原。 在電位學中，[Ni6(μ6-nypmpda)4Cl2]+在還原電位裡有兩對的氧化 還原電位、分別為E(red1) 1/2 = -0.08、E(red2) 1/2 = -0.63。

Abstact The aim of this study is to investigate the synthesis, structures, and correlative properties of linear hexanickel metal string complexes, where the ligand is N- (1,8-naphthyridin-7-yl)-N’-(pyrimidin-2-yl)pyridine-2,6-diamine (H2nypmpda). One novel unsymmetrical ligand (H2nypmpda) was synthesized by palladium-catalyzed cross-coupling of N-(6-bromopyridin-2-yl)-1,8-naphthyridin-2- amine (L2) with 2-aminopyrimidine. [Ni6(μ6-nypmpda)4Cl2](ClO4)2 (1) were synthesized by reaction of ligand H2nypmpda and nickel ion in melt naphthalene under basic condition. The one-electron reduced hexametal string complex [Ni6(μ 6-nypmpda)4Cl2]PF6 (2) was generated by reacting the hexanickel complex with the reductant N2H4. The structures of compounds 1 and 2 were characterized by single-crystal X-ray diffraction analysis. The X-ray structural studies reveal that the terminal nickel ions are five-coordinated and the inner nickel ions are four-coordinated. The difference in the structures 1 and 2 are the distances of Ni(1)-Ni(2) and Ni(2)-N, the Ni(1)-Ni(2) distance is shorter in 2 and Ni(2)-N distances are longer in 2. This attributes to the adding electron to dx2-y2 which is bonding to Ni(1)-Ni(2) and antibonding to Ni(2)-N bonds. The results of magnetic study show that complex 1 has a weak antiferromagnetic interaction between two terminal Ni(II) atoms and the coupling constant is -2.89 cm-1. Cyclic voltammetrical data show that complex 1 exhibits four couples ( E(red1) 1/2 = -0.07、E(red2) 1/2 = -0.24、E(red3) 1/2 = -0.46、E(red4) 1/2 = -0.68 ) and complex 2 has two couples ( E(red1) 1/2 = -0.08、E(red2) 1/2 = -0.63 ). These data indicate that complex 1 can be reduced easily.