| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 87 === The nature of metal-metal multiple bonding in dinuclear metal complexes is well understood. Our efforts to extend dinuclear metal complexes to form trinuclear metal complexes with syn-syn bis(α-pyridyl)amido ligand and late transition metal ions (M=RuΠ, RhΠ, CoΠ, NiΠ, CuΠ) have been reported.
In order to achieve a complete bonding scheme for the three-centred metal complexes, [Cr3(dpa)4Cl2](1), [Cr3(dpa)4(NCS)2](2), [Cr3(dpa)4F2](H2dpa)(BF4)2(3), [Cr3(dpa)4(OH)(CF3SO3)](CF3SO3)(4), [Cu3(dpa)4Br2](5) and [Cu3(dpa)4(NCS)2](6) were synthesized by using Hdpa ligands. The linear tri-nuclear metal chain was helically wrapped by four dpa- ligands to form a wire—like structure. All of these complexes were characterized by various spectroscopic methods, in particular mass spectrometry(FAB), X-ray diffraction and SQUID.
The crystal structures of [Cr3(dpa)4Cl2](1) complexes possesses a three-centred CrΠ-CrΠ-CrΠdelocalized triple bonds. The CrΠ-CrΠdistances are 2.3629(6)A. [Cr3(dpa)4(NCS)2](2) complexes possesses a asymmetry triple bonds on CrΠ-CrΠ-CrΠ unit with CrΠ-CrΠdistances are 2.277(2)A and 2.391(2)A, respectively. The chemical transformation of [Cr3II(dpa)4Cl2] by AgBF4 or AgCF3SO3 lead to the isolation of [Cr3III,II,II(dpa)4F2](H2dpa)(BF4)2(3) and [Cr3III,II,II(dpa)4(OH)(CF3SO3)](CF3SO3)(4) complexes which exhibit two-centred metal-metal quadruple bonds. In these two complexes, the short CrΠ-CrΠdistances of 2.0964(14)A for (3) and 1.9315(11)A for (4) are clearly consistent with the presence of localized quadruple bonds. The magnetic mearsurements indicate that there are two unpaired electrons in [Cr3II(dpa)4Cl2](1) complexes and three unpaired electrons contributed from the Cr3+(d3) species in [Cr3III,II,II(dpa)4F2](H2dpa)(BF4)2 (3) complexes.
In [Cu3(dpa)4Br2](5) and [Cu3(dpa)4(NCS)2](6) complexes, the CuΠ-CuΠdistances are 2.4667(8)A for (5) and 2.4530(2)A for (6), respectively. The magnetic measurement of (5) show an antiferromagnetic interaction between the copper(II) ions with the conpuling constant J = -242cm-1 and J’= -121cm-1, where J is involved in the spin coupling interaction between adjacent copper ions and J’ is involved in the interaction between terminal copper ions .
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