Syntheses and characterizations of the Unsymmetrical Ligand (H2nypmpda) and Its Hexanuclear Nickel Complexes

• Main Authors: Yu-kai Huang, 黃淯凱
• Other Authors: 彭旭明
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/66285122051566562908

碩士 === 國立臺灣大學 === 化學研究所 === 95 === 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.