Structural assignment of the stable carbonylhydridotris-(triphenylphosphine)iridium(II) cation and spectroscopic and voltammetric identification of the transient Ir(III) dication and its decomposition pathway

Alan M. Bond, David G. Humphrey, Dmitri Menglet, Georgii G. Lazarev, Ron S. Dickson, Truc Vu

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Abstract

Detailed studies on the electrochemical oxidation of the 18-electron IrH(CO)(PPh3)3 complex have been undertaken in dichloromethane. Under voltammetric conditions, the process IrH(CO)(PPh3)3 ⇆ [IrH(CO)(PPh3)3]+ + e-, which leads to the formation of the 17-electron [IrH(CO)(PPh3)3]+ cation, is chemically and electrochemically reversible. In contrast, the 16-electron dication [IrH(CO)(PPh3)3]2+, formed by a further one-electron oxidation process, is very reactive and undergoes a rapid internal redox reaction, [IrH(CO)(PPh3)3]2+ ⇆ [Ir(CO)(PPh3)3]+ + H+, to form the stable 16-electron [Ir(CO)(PPh3)3]+ species. In situ infrared (IR) spectroelectrochemical studies at low temperature, enable the v(CO) and v(IrH) IR bands to be obtained for [IrH(CO)(PPh3)3]+ as well as for transiently formed [IrH(CO)(PPh3)3]2+. EPR spectra obtained from frozen solutions of electrochemically generated [IrH(CO)(PPh3)3]+ have been simulated. In agreement with results of density functional calculations on related IrX(CO)(PPh)3 (X = H, Cl) complexes, the EPR data are consistent with [IrH(CO)(PPh3)3]+ having a square pyramidal structure. Data are compared with those available for oxidation of the analogous RhH(CO)(PPh3)3 complex. (C) 2000 Elsevier Science S.A.

Original languageEnglish
Pages (from-to)565-571
Number of pages7
JournalInorganica Chimica Acta
Volume300-302
DOIs
Publication statusPublished - 30 Apr 2000

Keywords

  • 18-electron complex
  • Electrochemical oxidation
  • Iridium(II) cation
  • Transient Ir(III) dication
  • Voltammetric oxidation

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