三吡啶二胺配基之四核異金屬(鈷/鎢及鎳/鉬)串錯合物的合成及研究

A series of tetranuclear heterometallic string complexes, [CoWCo2 (μ5-tpda)4(Cl)2](BF4) (1) , [CoWCo2(μ5-tpda)4(Cl)2] (2) , [CoWCo2 (μ5-tpda)4(NCS)2](PF6) (3) and [Mo2Ni2(μ5-tpda)4(Cl)(O)](PF6) (4) (tpda = tripyridyldiamino anion) were synthesized and characterized. The X-ray structural studies showed that all of them are helically wrapped by four all syn type H2tpda ligand, and have one 6B metal ion with square anti-prismatic geometry chelated by one pyridine N atom and the amido N atom of each of tpda2-. Axial ligands Cl- and NCS- are bonded to two Co ions for (1), (2) and (3), Cl- and O2- are bonded to Ni and Mo for (4). The distance between the middle 6B and nearby metal is larger than 3.0 A , which is elongated beyond the single-bond covalent radii of the metal atoms. The magnetic susceptibility showed that the μeff values of (1), (2), (3) and (4) at 300K are 2.59 , 2.44 and 2.01 B.M. respectively. The spin state of (1), (3) are the same, with Co2+ (S = 1/2), W4+ (S = 0), Co25+ (S = 1/2) configuration, which is close to the spin-only value 2.45 B.M. (2) is Co2+ (S = 1/2), W4+ (S = 0), Co2+(2) = Co2+(3) (S = 0) ,which is close to (1.73 B.M.) of spin-only value. The μeff of (4) is 3.04 B.M. , corresponding to Mo4+(1) (S = 0) , Mo4+ (2) (S = 0) , Ni2+(1) (S = 0) ; Ni2+(2) (S = 1) spin state.