Electron-transfer reactions of technetium and rhenium complexes. 2. Relative self-exchange rate of the M(I)/M(II) couples (M(DMPE)/sub 3/)/sup +/2+/, where M = Tc or Re and DMPE = 1,2-bis(dimethylphosphino)ethane

Journal Article · Wed Mar 23 04:00:00 EST 1988 · Inorg. Chem.; (United States)

DOI:https://doi.org/10.1021/ic00279a013· OSTI ID:5975674

Libson, K; Woods, M; Sullivan, J C; Watkins, II, J W; Elder, R C; Deutsch, E

The relative rates of self-exchange of the closely related d/sup 6//d/sup 5/ couples (Tc(DMPE)/sub 3/)/sup +/2+/ and (Re(DMPE)/sub 3/)/sup +/2+/ have been determined by two independent applications of the Marcus theory. (1) The rates and equilibrium constants governing the cross-reactions between (Re(DMPE)/sub 3/)/sup +/ and ((NH/sub 3/)/sub 5/RuL)/sup 3+/ (L = 4-picoline, pyridine, and isonicotinamide) were measured in a 0.100 M LiCl and 0.001 M HCl aqueous medium and compared to equivalent data previously obtained for the reaction of (Tc(DMPE)/sub 3/)/sup +/ with the same three Ru(III) complexes in this medium. (2) EXAFS measurements were used to obtain average Re(I)-P and Re(II)-P bond lengths for the (Re(DMPE)/sub 3/)/sup +2/2+/ complexes, and these data were compared to equivalent data available for the (Tc(DMPE)/sub 3/)/sup +/2+/ complexes. The difference in bond lengths, (M/sup II/-P) - (M/sup I/-P), is less for the Re couple than for the Tc couple (0.054 vs 0.068 /angstrom/), and within the Marcus formalism this leads directly to a structurally determined value of k/sub ex//sup Re//k/sub ex//sup Tc/ = 2. Thus, the kinetically observed, slightly greater rate of self-exchange of the (Re(DMPE)/sub 3/)/sup +/2+/ couple is seen to be due entirely to the somewhat smaller structural distortions suffered by the inner coordination sphere of the Re complex during electron transfer. The absolute self-exchange rates of the (Re(DMPE)/sub 3/)/sup +/2+/ and (Tc(DMPE)/sub 3/)/sup +/2+/ couples are calculated to be 4 /times/ 10/sup 6/ M/sup /minus/1/ s/sup /minus/1/ and 2 /times/ 10/sup 6/ M/sup /minus/1/ s/sup /minus/1/, respectively (25/degree/C, /mu/ = 0.10 M). 17 refs., 2 figs., 5 tabs.

• Research Organization: Univ. of Cincinnati, OH (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5975674
• Journal Information: Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 27:6; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CHEMICAL REACTIONS
DATA
EXPERIMENTAL DATA
INFORMATION
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
REDOX REACTIONS
REFRACTORY METAL COMPOUNDS
RHENIUM COMPOUNDS
TECHNETIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS