Synthesis of Multi-Nuclear Complexes with Highly Steric Ligands

• Main Authors: Duan-Yen Lu, 呂端晏
• Other Authors: Yi-Chou Tsai
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/19894570493468881945

碩士 === 國立清華大學 === 化學系 === 95 === In order to synthesize low-coordinate multi-nuclear complexes, we prepared two sterically demanding ligands, H2[2,6-(NDipp)2-4-MeC5H2N] and H2[Me2Si(NDipp)2] (Dipp = 2,6-i-propylphenyl). Their corresponding dilithiated salts were subsequently prepared and then reacted with copper(I) iodide in tetrahrdrofuran, cadmium(II) chloride in ether, and zinc(II) bromide in ether, respectively. From these said reactions, we successfully isolated multi-nuclear complexes and they are fully characterized by multi-nuvlear NMR spectroscopy and single crystal X-ray diffraction. Li(THF)3{Cu3[μ3-η1:η1:η1-2,6-(NDipp)2-4-MeC5H2N]2} (3) and [K(18-crown-6)]{Cu4[μ4-η2:η2-Me2Si(NDipp)2]2(μ-I)} (4) exhibit fluorescence with low quantum yield. Due to the d10-d10 interactions, the Cu-Cu distances in complexes 3 and 4 are short ( 2.426(1)-2.486(2) Å). On the other hand, two iso-structure dicadmium and dizinc complexes Cd2[μ-η2-Me2Si(NDipp)2]2 (5) and Zn2[μ-η2-Me2Si(NDipp)2]2 (7) supported by two sterically encumbered diamido ligands Me2Si(NDipp)2 could be isolated in good yields, in which the metal-metal axes are perpendicular to the Si-Si linkage. Upon reduction of 5, a novel tetracadmium complex, [K(18-crown-6)]2{Cd[(η-Me2Si(NDipp)2)Cd(η2-Me2Si(NDipp)2)]}2 (6), with a Cd-Cd bond was prepared. It is interesting to note that complex 6 displays two different types of cadmium metal centers. One, Cd(II), is ligated by three nitrogen atoms, and the other, Cd22+, is coordinated by two nitrogen atoms. A possible mechanism to explain the formation of complex 6 was proposed based on 113Cd-NMR data. On the other hand, while complexes Zn2[μ-η2-Me2Si(NDipp)2]2 (7) and Zn2[μ-η1:η2-2,6-(NDipp)2-4-MeC5H2N]2(THF)2 (9) were also treated with KC8 in tetrahydrofuran, we obtained [K-C-2,2,2]2[Zn(η2-Me2Si(NDipp)2)]2 (8), where the Zn-Zn bond is parallel with the Si-Si linkage, and [K-18-crown-6]{KZn2[μ-η1:η2-2,6-(NDipp)2-4-MeC5H2N]2} (10) exhibiting a remarkable three-center and two-electron Zn-K-Zn bonding. The mechanism for the interesting structural transformations from 7 to 8 involving Zn-Zn bonds was proposed to proceed through an intermediate {Zn2[μ-η2-Me2Si(NDipp)2]2}‾ which was verified with the aid of DFT calculations. Complex 10 displays fluorescence property with low quantum yield.