Structural and kinetic investigations of a Tc(III)/Tc(II) redox couple. X-ray crystal structures of trans-(Tc/sup II/(DPPE)/sub 2/Cl/sub 2/) and trans-(Tc/sup III/(DPPE)/sub 2/Cl/sub 2/)NO/sub 3/ x HNO/sub 3/, where DPPE = 1,2-bis(diphenylphosphino)ethane
The components of a reversible Tc(III/II) redox couple have been characterized by single-crystal x-ray analysis and the crystal parameters are reported. Oxidation of the Tc(II) complex to the Tc(III) form causes a shortening of the Tc-Cl bond by 0.105 (2) /angstrom/, consistent with the ionic nature of this interaction. Conversely, oxidation from Tc(II) to Tc(III) causes a lengthening of the Tc-P bond by 0.072 (2) /angstrom/, consistent with the domination of this interaction by ..pi..-back-bonding from Tc to P. The magnitudes of these bond length changes are used to predict the inner-sphere reorganization barrier to electron transfer of the trans-Tc(DPPE)/sub 2/Cl/sub 2//sup +/0/ couple to be only ca. 2.6 kcal/mol. Preliminary kinetic studies in nonaqueous media confirm that trans-(Tc/sup II/(DPPE)/sub 2/X/sub 2/) (X = Cl, Br) complexes are facile electron-transfer partners for a variety of 1-equiv oxidants. The rate of reduction of ((en)/sub 2/Co(S(CH/sub 2/C/sub 6/H/sub 4/CH/sub 3/)CH/sub 2/CH/sub 2/NH/sub 2/))/sup 3 +/ by trans-(Tc/sup II/(DPPE)/sub 2/Cl/sub 2/) in acetonitrile (25/degrees/C; ..mu.. = 0.10 M) is 3.0 (7) x 10/sup 4/ M/sup -1/ s/sup -1/. 56 references, 1 figure, 6 tables.
- Research Organization:
- Univ. of Cincinnati, OH (USA)
- DOE Contract Number:
- W-31-109-ENG-38
- OSTI ID:
- 6236253
- Journal Information:
- Inorg. Chem.; (United States), Vol. 27:20
- Country of Publication:
- United States
- Language:
- English
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ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALKANES
REDOX REACTIONS
AROMATICS
CHLORINE COMPOUNDS
NITRATES
ORGANIC PHOSPHORUS COMPOUNDS
TECHNETIUM COMPLEXES
EXPERIMENTAL DATA
CHEMICAL REACTIONS
COMPLEXES
DATA
HALOGEN COMPOUNDS
HYDROCARBONS
INFORMATION
NITROGEN COMPOUNDS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
TRANSITION ELEMENT COMPLEXES
400400* - Electrochemistry
400201 - Chemical & Physicochemical Properties