含N,N’−二(2−嘧啶)甲咪配位基與多核金屬化合物之研究

Abstract

Abstract This dissertation discusses the chemistry of polynuclear metal complexes containing anion of N,N’-bis(pyrimidine-2-yl)formamidine ligand. The salts of d10-metal react instantaneously with KL1 (L1 = anion of N,N’-bis(pyrimidine-2-yl)formamidine, HL1) in THF, producing bimetallic complexes of the types [M2(L1)3](X) (M = Zn(II), X = I3-, 1a; M = Zn(II), X = NO3-, 1b; M = Zn(II), X = ClO4-, 1c; M = Cd(II), X = NO3-, 2a; M = Cd(II), X = ClO4-, 2b) and Hg2(L1)2X2 (X = Cl, 3a; Br, 3b; I, 3c). New tridentate and tetradentate coordination modes were observed for the L1 ligands and their fluxional behaviors investigated by measuring variable- temperature 1H NMR spectra. Complexes 2a and 2b, which possess only tetradentate coordination modes for the L1 ligands in the solid state show larger free energy of activation (孱c╪) for the exchange than complexes 1a - c and 3a - c with tetradentate and/or tridentate coordination modes. Complexes 1a - c and 3a - c are the first dinuclear Zn(II) and Hg(II) complexes containing formamidinate ligands. Moreover, the separation between the two Hg(II) atoms are 3.47(1), 3.49(1) and 3.53(1) A for complexes 3a - c, respectively, similar to the sum of van der Waals radii of two Hg(II) atoms which is 3.50(7) A. All the complexes exhibit emissions with λem in the range form 391 to 472 nm and the nature of the anions hardly change the emission wavelengths of the complexes with the same metal centers. Reactions of KL1 with divalent copper salt CuX2 afforded linear trinuclear complex of the type [Cu3(L1)4](X)2 (X = NO3-, 4a; ClO4-, 4b). The copper atoms of complexes 4a and 4b are helically bridged and/or chelated by four L1 ligands, resulting in four different coordination modes for the L1 ligands. While three of the four L1 ligands in complexes 4a and 4b are coordinated to the copper atoms in tetradentate fashions, the other one is coordinated to the copper atoms in a tridentate fashion, leaving one of the pyrimidyl nitrogen atom uncoordinated. In the tetradentate fashion, a pair of the L1 ligands form the coordination, with the two amine nitrogen atoms chelating to the central copper atom, while one L1 ligand forms the coordination mode, which features chelation by one pyrimidyl and one adjacent amine nitrogen atoms. Reactions of K[Cu4(L1)3(SCN)2] with Cu(CH3COO)2 and Mo2(CH3COO)4 afforded linear tetranuclear complexes of the type Cu2(M)2(L1)4(SCN)2 (M = Cu(II), 5; M = Mo(II), 6). The four metal atoms of complexes 5 and 6 are helically bridged by four tetradentate L1 ligands. Fluxional behavior was observed for complex 6 in solution. By the DNMR analysis, the free energy of activation (孱c╪) for the exchange is 13.65 kcal mol−1 at 275 K (Tc), and the rate constant of exchange (Kc) is 77.71 s−1 for 6. Reactions of NaL1 with AgSCN, Co(SCN)2 and CoBr2 afforded complexes Ag4(L1)4, 7; Co2(L1)4, 8 and Na2[Co6(L1)6(μ3-O)2(μ4-O)(Br)2], 9, respectively. The complex 7 is a cyclic tetranuclear complex containing only Ag(I) atoms and the L1 ligands are coordinated to the silver atoms in bidentate fashion through the two central amine nitrogen atoms, leaving the pyrimidyl nitrogen atoms uncoordinated. Complex 8 is a bimetallic complex with the L1 ligands coordinating to the metal centers in a tridentate fashion. The separation between the two Co(II) atoms is 3.504(1) A. Complex 9 is a hexanuclear complex with four disordered Co atoms. Each structure consists of three oxygen atoms, where one oxygen atom is centered in a square planar of four Co atoms and the other two oxygen atoms are centered in a trigonal planar of three Co atoms. The reactions of Mo2(CR3COO)4 (R = H or F) with different equivalents of HL1 and N-(2-pyrimidinyl)formamide (HL2) afforded dimolybdenum complexes of the types NaMo2(L1)4(CF3COO), 10; Mo2(L1)2(L2)(CH3COO), 11; trans-Mo2(L1)2(L2)2, 12; cis-Mo2(L1)2(L2)2, 13 and Mo2(L2)4, 14. Complexes 12 and 13 establish the first pair of trans and cis forms of dimolybdenum complexes containing formamidinate ligands. The L1 ligands in 10 - 13 are bridged to the metal centers through two central amine nitrogen atoms, while the L2 ligands in 11 - 14 are bridged to the metal centers via one pyrimidyl nitrogen atom and the amine nitrogen atom. The Mo-Mo distances of complexes 10 [2.1084(6) A], 11 [2.0951(17) A], 12 [2.103(1) A] and 13 [2.1017(3) A], which contain both Mo---N and Mo---O axial interactions, are slightly longer than those of complex 14 [2.0826(12) - 2.0866(10) A] which has only Mo---O interactions.