Oxidation of Ir(CO)(dppe)2+ with halogens affords cw-IrX(CO)(dppe)22+ (X = Cl, Br) while oxidation with HBF4affords cis-IrH(CO)(dppe)22+. The species trans-IrX(CO)(dppe)22+ (X = Cl, Br) are prepared by the oxidation of Ir(CO)(dppe)2+ with nitrosonium ion in the presence of Cl- or Br-. The complex transs-IrH(CO)(dppe)22+ is most convenientlyprepared by protonation of [Ir(dppe)2]BF4 with HBF4-Et2O to afford the intermediate IrH(dppe)22+, followedby CO addition. In contrast, both cis-and trans-IrCl(CO)(dppe)22+ species are formed by the electrochemical oxidation of Ir(CO)(dppe)2+ in chloride media. The trans isomer is reduced at a more negative potential and is thus thermodynamically the more stable. Reversible deprotonation of cis-[IrH(CO)(dppe)2][BF4]2 by chloride implies that the acidity of this compound is of the order of that of HC1, unusually strong for a third-row transition-metal hydrido complex.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry