Synthesis of polynuclear hetero-metal complexes of Bi-p, -d, and -f block elements

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 12640543
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Inorganic chemistry
• Research Institution: University of the Ryukyus
• Principal Investigator: ASATO Eiji Faculty of Science, Department of Chemistry, Biology, and Marine Sciences, Associate Professor, 理学部, 助教授 (10222580)
• Project Period (FY): 2000 – 2002
• Keywords: Polynuclear hetero-metal comnlex / Bismuth complex / Polymetallic oxide / X-ray crystal structure analysis / Powder X-ray diffraction / Thermal decomposition / Cluster comniex

Research Abstract

In order to establish rational preparative method to create Bi-based hetero-metal dinuclear complexes, a new phenol-based ligand H_6L was prepared. Reaction of H_6L with Bi(N0_3)_3・5H_2O afforded mononuclear Bi complex [Bi(H_3L)]・H_2O, where Bi atom is trapped into "Bi-recognition site" embedded in the ligand.This complex still contains an empty coordination site for a second metal ion, and indeed reacts with a variety of d-block and p-block elements.Successfully isolated dinuclear complexes are as follows ; Bi-V(IV)=O, -Cr(III), -Mn(III), -Fe(III), -Co(llI), -Ni(II), -Cu(II), -Zn(II), and -AI(III).As potential precursors for polymetallic oxides, thermal decomposition process of these complexes was examined using TGA analysis and XRD measurement.As a representative case, Bi-Cu hetero-nuclear complex loses all of its organic ingredients at around 300℃ to become a mixture of Bi_2CuO_4, Bi_2O_3, and CuO.The latter two ingredients further react each other at higher temperatures, and finall y causing disappearance of Bi_2O_3 ingredient above 600℃.
Another approach to hetero-metal clusters was also examined.A commercially available ligand N-2-hydroxyethyl)iminodiacetic acid(H_3heida)reacts with Bi ion in a mixed solvent of aqueous ammonia and methanol to give trinuclear Bi complex (NH_4)[Bi_3(heida)_3(OH)]・6H_2O・MeOH.Its structure is characterized as an incomplete cuban[Bi_3(μ-O_<alkoxo>alkoxo)_3(μ_3-OH)], where the three Bi atoms are bridged by the hydroxide ion (μ_3-OH) and adjacent Bi pairs are further bridged by the alkoxo oxygen of heida^<3->.The metal deficient position of the pre-cubane is occupied by NH^+_4 through hydrogen bonding toward the three bridging alkoxo oxygens.The NH^+_4 can be easily replaced by K^+ to form a mixed cluster [Bi_3K(μ_3-O)_4].This finding suggests that the trinuclear pre-cubane may function as a potential precursor for the mixed clusters of [Bi_3M(μ_3-O)_4] type, where M is d-block and p-block elements, while no such mixed metal clusters have been obtained yet.