A study on the coordinative versatility of the zwitterionic S,N,S ligand EtNHC(S)Ph2P=NPPh2C(S)NEt in its anionic, neutral and cationic forms - determination of absolute pKa Values in CH 2Cl2 of RhI complexes

Massimiliano Delferro, Daniele Cauzzi*, Roberto Pattacini, Matteo Tegoni, Claudia Graiff, Antonio Tiripicchio

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

The coordination properties of EtNHC(S)Ph2P=NPPh 2C(S)-NEt (HEtSNS) towards RhI species derived from [Rh(CO)2-Cl]2 and [Rh(cod)Cl]2 (cod = 1,5-cyclooctadiene) were studied. This ligand is an amphoteric zwitterion, which forms the H2EtSNS+ cation upon protonation and the EtSNS- di-anion-cation upon deprotonation. All three forms coordinate to metal centers. Their geometrical versatility allows many coordination fashions: S-monodentate; S,S-bidentate (with a bite angle spanning from 90 to 180°); S,N,S-tridentate; N,N,N-tridentate; and S,S-bridging, as determined by X-ray diffraction methods. The [Rh(CO)EtSNS] complex is a biprotic base; its conjugated acids are [Rh(CO)HEtSNS]+ and [Rh(CO)H2EtSNS] 2+, and their pKa values were determined in dichloromethane solutions. In this triad of compounds, which are geometrically similar, the RhI metal center features variable charge density as confirmed by the νCO infrared absorption frequency.

Original languageEnglish (US)
Pages (from-to)2302-2312
Number of pages11
JournalEuropean Journal of Inorganic Chemistry
Issue number14
DOIs
StatePublished - May 2008

Keywords

  • Acid-base properties
  • Coordination modes
  • Rhodium
  • Zwitterions

ASJC Scopus subject areas

  • Inorganic Chemistry

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