| Abstract |
The organonitrile or carbonyl complexes cis-[ReCl(RCN)(dppe)(2)] (1) (R = 4-Et2NC6H4 (1a), 4-MeOC6H4 (1b), 4-MeC6H4 (1c), C6H5 (1d), 4-FC6H4 (1e), 4-ClC6H4 (1f), 4-O2NC6H4 (1g), 4-ClC6H4CH2 (1h), t-Bu (1i); dppe = Ph2PCH2CH2PPh2), or cis-[ReCl(CO)(dppe)(2)] (2), as well as trans-[FeBr(RCN)(depe)(2)] BF4 (3) (R = 4-MeOC6H4 (3a), 4-MeC6H4, (3b), C6H5 (3c), 4-FC6H4 (3d), 4-O2NC6H4 (3e), Me (3f), Et (3g), 4-MeOC6H4CH2 (3h); depe = Et2PCH2CH2PEt2), novel trans-[FeBr(CO)(depe)(2)]BF4 (4) and trans-[FeBr2(depe)(2)] (5) undergo, as revealed by cyclic voltammetry at a Pt-electrode and in aprotic non-aqueous medium, two consecutive reversible or partly reversible one-electron oxidations assigned as Re-I —> Re-II —> Re-III or Fe-II —> Fe-III —> Fe-IV. The corresponding values of the oxidation potentials E-I(1/2)ox and E-II(1/2)ox (waves I and II, respectively) correlate with the Pickett s and Lever s electrochemical ligand and metal site parameters. This allows to estimate these parameters for the various nitrile ligands, depe and binding sites (for the first time for a Fe-III/(IV) couple). The electrochemical ligand parameter show dependence on the electron-richness of the metal centre. The values of E-I(1/2)ox for the Re-I complexes provide some supporting for a curved overall relationship with the sum of Lever s electrochemical ligand parameter. The Pickett parametrization for closed-shell complexes is extended now also to 17-electron complexes, i.e. with the 15-electron Re-II and Fe-III centres in cis-\[ReCl(dppe)(2)]\(+) and trans-\FeBr(depe)(2)\(2+), respectively. |
