New low-spin Co(II) complexes with novel tripodal 1,1,1-tris(dimethylphosphinomethyl)ethane ligand: Electron transfer kinetics and spectroscopic characterization of Co(II)P6 and Co(II)P3S3 ions in aqueous solution

S. Iwatsuki, K. Obeyama, N. Koshino, S. Funahashi, K. Kashiwabara, T. Suzuki, H. D. Takagi

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Substitution-inert Co(II) complexes with tripodal 1,1,1-tris(dimethylphosphinomethyl)ethane were produced in aqueous solution by the controlled-potential electrolysis. EPR studies indicated that the Co(II)P6 and Co(II)P3S3 species are in the low-spin t2g6eg1 state. The analyses of the absorption spectra of the Co(II) species in solution indicated significant Jahn-Teller distortion in Co(II)P6 and Co(II)P3S3 ions as expected for the low-spin d7 electronic configuration, while less distortion was observed for the Co(II)S6 ion. Kinetic studies of the redox reactions involving these Co(III/II) species confirmed that the electron self-exchange reactions for the Co(III/II)P6 and Co(III/II)P3S3 couples are relatively fast (kex ∼ 1 × 104 dm3 mol-1 s-1), which is consistent with the results for other low-spin - low-spin Co(III/II) couples. It was concluded that the nephelauxetic effect of the P-donor atom stabilizes the low-spin state in Co(II), and that the rather rapid electron exchange rates for these Co(III/II) couples were explained by the lack of the spin reorganization process required for the ordinary low-spin - high-spin Co(III/II) couples.

Original languageEnglish
Pages (from-to)1344-1351
Number of pages8
JournalCanadian Journal of Chemistry
Volume79
Issue number9
DOIs
Publication statusPublished - Jan 1 2001
Externally publishedYes

Keywords

  • Cobalt(III/II)
  • EPR study
  • Electron transfer
  • Kinetics
  • Spin state

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Organic Chemistry

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