Photocalorimetry. 5. Enthalpies of reaction of M/sub 2/(CO)/sub 10/ (M = Mn, Re) compounds with iodine in cyclohexane solution at 25 /sup 0/C

Journal Article · Wed Dec 03 23:00:00 EST 1986 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100283a021· OSTI ID:7202340

Harel, Y; Adamson, A W

Enthalpies of reaction of Mn/sub 2/(CO)/sub 10/, Re/sub 2/(CO)/sub 10/, and MnRe(CO)/sub 10/ with iodine in cyclohexane solution are reported for 25 /sup 0/C, as obtained by the method of photocalorimetry. The photochemical reactions give the M(CO)/sub 5/I products cleanly with quantum yields of 0.41 +/- 0.01 (436 nm), 0.57 +/- 0.02 (366 nm), and 0.42 +/- 0.05 (366 nm) for the above systems, respectively, in good agreement with literature values. The ..delta..H/sub s,298/ values (s denoting solution) are -44.9 +/- 2.0 kcal for Mn/sub 3/(CO)/sub 10/(s) + I/sub 2/(s) = 2Mn(CO)/sub 5/I(s), -37.6 +/- 3.8 kcal for the analogous reaction of Re/sub 2/(CO)/sub 10/, and -55.7 +/- 3.0 kcal for MnRe(CO)/sub 10/(s) + I/sub 2/(s) = Mn(CO)/sub 5/I(s) + Re(CO)/sub 5/I(s). Also reported are the heats of solution of Mn/sub 2/(CO)/sub 10/(c) (c denoting crystalline state), Re/sub 2/(CO)/sub 10/(c), and Re(CO)/sub 5/I(c) in cyclohexane at 25 /sup 0/C, the respective values being 8.6 +/- 0.5, 8.2 +/- 0.5, and 8.3 +/- kcal mol/sup -1/. In the case of the manganese system, comparison of ..delta..H/sub c//sup 0/ (obtained by correcting ..delta..H/sub s,298/ for heats of solution) with that obtained from the literature values of ..delta..H/sub f//sup 0//sub 298/ of Mn/sub 2/(CO)/sub 10/(c) and of Mn(CO)/sub 5/I(c) shows a discrepancy amounting to a correction of 9.6 kcal mol/sup -1/ if assigned entirely to the former ..delta..H/sub f//sup 0//sub 298/ value and of -4.6 kcal mol/sup -1/ if assigned entirely to the latter one. Combination of the ..delta..H/sub s,298/ values indicates that the Mn-Re bond in MnRe(CO)/sub 10/ is weaker by 15 kcal than the average of the corresponding metal-metal bond energies in Mn/sub 2/(CO)/sub 10/ and Re/sub 2/(CO)/sub 10/. The result contrasts considerably with that derived from bond energy values obtained from literature reports of ionization and appearance potentials.

• Research Organization: Univ. of Southern California, Los Angeles
• OSTI ID: 7202340
• 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

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
400500* -- Photochemistry
ALKANES
CALORIMETRY
CARBONYLS
CHEMICAL REACTIONS
CHEMISTRY
CYCLOALKANES
CYCLOHEXANE
DATA
ELEMENTS
ENTHALPY
EXPERIMENTAL DATA
HALOGENS
HYDROCARBONS
INFORMATION
IODINE
MANGANESE COMPOUNDS
MEDIUM TEMPERATURE
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
PHYSICAL PROPERTIES
REACTION HEAT
REFRACTORY METAL COMPOUNDS
RHENIUM COMPOUNDS
SOLUTION HEAT
THERMODYNAMIC PROPERTIES
THERMODYNAMICS
TRANSITION ELEMENT COMPOUNDS