Calorimetric study of the Lewis acid properties of coordinatively unsaturated organoiridium(III) species

T. W. Leung, M. J. Hintz, L. T. Chan, A. D. Sherry, D. M. Blake

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Abstract

The Lewis acid character of a series of coordinatively unsaturated iridium(III) complexes of the type {IrCl2R[P(C6H5)3]2} (R is C(O)CFnH3-n (n = 1, 2, or 3), -S(O)2R′ (R′ = CH3, C2H5, or CF3), or CH3) has been studied by calorimetric and spectroscopic methods. Enthalpy data for addition of pyridine as a function of R are interpreted in terms of a trans influence series for the R groups. This thermochemical trans influence series is compared with that derived from the trends in iridium-chlorine stretching frequencies in model compounds having R trans to Cl. The enthalpy change and equilibrium constant for pyridine addition to the complex in which R = C(O)CF3 were determined in six solvents. The trends in enthalpy changes and equilibrium constants for addition of a series of ten bases to the trifluoroacetyl complex in methylene chloride are interpreted in terms of base strength and steric factors. The enthalpy change for pyridine addition to {IrClXCH3[P(C6H5)3]2} (X = Cl, Br, -NCO, NO2, or CH3CO2) in methylene chloride reveals that the cis influence of X is low. Representative examples of the octahedral adducts {IrCl2R[P(C6H5)3] 2·B} have been isolated and characterized. In each case the base B is found to add stereospecifically trans to the substituent R.

Original languageEnglish (US)
Pages (from-to)2606-2612
Number of pages7
JournalInorganic Chemistry
Volume16
Issue number10
Publication statusPublished - 1977

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ASJC Scopus subject areas

  • Inorganic Chemistry

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