| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2006: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2005: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
The metal-metal interaction in polynuclear transition metal complex is mainly governed by the nature, oxidation state and geometry of the central metal ion. Because the extent of metal-metal interaction can be controlled by the change of oxidation state of metal ions and therefore there is possibility to isolate mixed-valent compounds, the redox properties of polynuclear transition metal complexes have attracted much attention. In order to study the response of molecules with metal-metal interactions towards external stimuli such as magnetic field, electric potential, excitation by radiation, or heat, we have synthesized polynuclear complexes of pyrazolates and pyridinethiols, and studied their properties. Followings are the summary of our results.
(1) The precursor with intramolecular hydrogen bonding, [Pd_2(μ-Rpz)_2(Rpz)_2(Rpzh)_2] (R=3-t-butyl), gave tetranuclear complexes of Pd_2M'_2 type (M' = Ag, Au). The detailed study on the reaction of HT-[Pd_2(μ-3-t-Bupz)_2(3-t-Bupz)_2(3-tBupz
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H)_2] with Ag^I ion and Au^I complex enabled is to isolate two linkage isomers of tetranuclear complexes, head-to-head isomer (HH isomer) and head-to-tail isomer (HT isomer). Because a facile stereochemical rearrangement of the linkage isomers was observed at elevated temperature, it was followed by ^1H NMR spectroscopy.
(2) To synthesize Pt-Pt bonds in cyclic platinum trimer, the best-fit complex is probably the pyrazolato-bridged trinuclear platinum(II) complex, [Pt_3(μ-pz)_6] (pz = pyrazolate). In order to give an answer to the question whether direct Pt-Pt bond can be formed in the cyclic platinum trimer or not, we have conducted the oxidation of [Pt_3(μ-pz)_6] and succeeded, for the first time, the isolation and characterization of the two-electron oxidized species, [Pt_3Br_2(μ-Pz)_6], as well as the assignment of the electronic spectra of them. Very interestingly, the oxidized species show "valence-detrapping" behavior in solution. We concluded that the valence-detrapping occurs in the solution state in associative manner via either approach of solvent DMF molecule to the Br-coordinated Pt center or approach of Br^- to the uncoordinated Pt atom in the presence of excess Br^- anion.
(3) Although several ESBO rhenium(IV) complexes have been synthesized so far, they are all diamagnetic. We have succeeded in the synthesis of an ESBO rhenium(IV) complex of pyridine-2-thiolate, which exhibits temperature-dependent magnetic properties showing the existence of ^3(δδ^*) excited triplet state. Less
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