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Photocalorimetry. 4. Enthalpies of substitution reactions of rhodium(III) and iridium(III) pentaammine halides and of ruthenium(II) hexaammine

Journal Article · · J. Phys. Chem.; (United States)
DOI:https://doi.org/10.1021/j100283a020· OSTI ID:6952112
Photocalorimetric enthalpies of aquation at 25 /sup 0/C are reported for Rh(NH/sub 3/)/sub 5/X/sup 2 +/, X = Cl/sup -/, Br/sup -/, and I/sup -/; for Ir(NH/sub 3/)/sub 5/X/sup 2 +/, X = Cl/sup -/ and I/sup -/; and for Ru(NH/sub 3/)/sub 6//sup 2 +/. ..delta..H = 6.1 and 17.4 kcal mol/sup -1/ for the chloride aquation of Rh(NH/sub 3/)/sub 5/Cl/sup 2 +/ and Ir(NH/sub 3/)/sub 5/Cl/sup 2 +/, respectively, and 0.2, 0.2, 2.3, and 7.2 kcal mol/sup -1/ for the ammonia aquation reactions of Rh(NH/sub 3/)/sub 5/Br/sup 2 +/, Rh(NH/sub 3/)/sub 5/I/sup 2 +/, Ir(NH/sub 3/)/sub 5/I/sup 2 +/, and Ru(NH/sub 3/)/sub 6//sup 2 +/, respectively. The reactions were studied in acidic solution so that the product ammonia appeared as ammonium ion. Comparison of the data, including published results for some Cr(III) and Co(III) complexes, allows a tentative ordering of metal-ligand bond strengths in terms of metal ion and in terms of ligand. Thus, D/sub M-NH/sub 3//-D/sub M-OH/sub 2//, D denoting bond dissociation energy, varies with metal M according to the spectrochemical series Ir(III) greater than or equal to Rh(III) approx. Ru(II) > Co(III) > Cr(III).
Research Organization:
Univ. of Southern California, Los Angeles
OSTI ID:
6952112
Journal Information:
J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 90:25; ISSN JPCHA
Country of Publication:
United States
Language:
English