Preparation, structure, and dynamic and electrochemical behaviors of dinuclear rhodium(I) complexes with bridging formamidinato ligands

Yuki Ide, Takahisa Ikeue, Yusuke Kataoka, Ryoko Inoue, Mikio Nakamura, Daisuke Yoshioka, Masahiro Mikuriya, Tatsuya Kawamoto, Makoto Handa

Research output: Contribution to journalArticle

Abstract

Dinuclear rhodium(I) complexes, [Rh(4-Me-pf) (cod)]2 (1), [Rh(3,5-Me2-pf) (cod)]2 (2), [Rh(4-Me-pf) (nbd)]2 (3), [Rh(3,5-Me2-pf) (nbd)]2 (4), and [Rh(2,6-F2-pf) (nbd)]2 (5), have been synthesized and characterized by X-ray structure analysis, 1H, 13C, and 19F NMR, UV-vis, ESI-TOF-MS, and elemental analysis. In these complexes, two rhodium atoms are bridged by two formamidinato ligands and each rhodium atom is coordinated by one chelating cod or nbd ligand to form an approximately square planar coordination structure with two nitrogen atoms and two double bonds. The Rh··Rh distances are in the range of 3.2668 to 2.9726 Å, suggesting a direct bonding interaction between two rhodium atoms. Variable temperature NMR studies in CD2Cl2 solution have revealed that 1-5 exhibit a novel dynamic behavior, that is, an interconversion between two enantiomers. The activation parameters for racemization have been determined by the line shape analyses of the 1H and 19F NMR spectra taken at various temperatures. Variable temperature NMR studies have also revealed that the rotation rates of the four aryl groups around N-C(aryl) bonds are extremely different in each complex. The cyclic voltammetry study has shown that the oxidation potentials corresponding to Rh2 3+/Rh2+ are 0.41 V in the cod complexes (1 and 2) while those in the nbd complexes (3-5) have shown negative shift by ca. 0.2 V. The reasons for the difference in dynamic behaviors and redox properties among these complexes have been discussed.

Original languageEnglish
Pages (from-to)92-103
Number of pages12
JournalJournal of Organometallic Chemistry
Volume803
DOIs
Publication statusPublished - 2016 Feb 1
Externally publishedYes

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Keywords

  • Crystal structures
  • Cyclic voltammogram
  • Dirhodium(I) complexes
  • Dynamic NMR
  • Formamidinato ligand

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Organic Chemistry
  • Physical and Theoretical Chemistry
  • Materials Chemistry
  • Biochemistry

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