Electron-transfer reactions of tetrakis-(.mu.-acetato)dirhodium(II) and the self-exchange rate of the Rh2(OAc)4+/Rh2(OAc)4 couple

1983 ◽  
Vol 22 (2) ◽  
pp. 351-353 ◽  
Author(s):  
Razak Bin Ali ◽  
Kossol Sarawek ◽  
Anne Wright ◽  
Roderick D. Cannon
Keyword(s):  
Electron Transfer ◽  
Exchange Rate ◽  
The Self ◽  
Transfer Reactions ◽  
Electron Transfer Reactions

Electron transfer reactions of nickel complexes of 1,4,7-triazacyclodecane

1985 ◽  
Vol 63 (11) ◽  
pp. 2983-2989 ◽  
Author(s):  
M. G. Fairbank ◽  
A. McAuley ◽  
P. R. Norman ◽  
O. Olubuyide
Keyword(s):  
Electron Transfer ◽  
Exchange Rate ◽  
Proton Transfer ◽  
Electrochemical Oxidation ◽  
Rate Constant ◽  
Aqueous Media ◽  
Nickel Complexes ◽  
Outer Sphere ◽  
The Self ◽  
Transfer Reactions

The preparation of [Ni(1,4,7-triazacyciodecane)2]3+, (Ni(10-aneN3)23+) is described. The existing procedure has been modified leading to good yields of the ligand trihydrochloride. The nickel(II) analogue (reported previously) is oxidised in a facile manner, either by Co3+aq in acidic aqueous media or by NO+ in CH3CN. Since the octahedral NiN6, chromophore is retained upon electron transfer, outer sphere reactions both of the Ni(II) and Ni(III) species have been studied. Rates of oxidation by various nickel(III) macrocycles have been measured and details are provided. Electrochemical oxidation of the Ni(II) complex is consistent with E0(Ni(10-aneN3)23+/2+) = 0.997 V (vs. NHE). The data have been used in a Marcus correlation, leading to the self-exchange rate k11 for the couple (Ni(10-aneN3)23+/2+) = (2 ± 1) × 104 M−1 s−1. This value is compared with other data derived using octahedral Ni(II)/Ni(III) centres. The oxidation of the Ni(II) complex by Co(III)aq has been studied in both protonated and deuterated media. There is no evidence for any proton transfer (from the N—H) being coupled to the electron transfer step. The observed rate constant for the reaction of Co3+ with Ni(II)(10-aneN3)22+ (550 M−1 s−1) may be compared with the calculated outer sphere rate (270 M−1 s−1). An estimate of k11 (CoOH2+/+) ~ 3 M−1 s−1 for the CoOH2+/+ exchange is discussed.

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