OXIDATIVELY INDUCED REDUCTIVE ELIMINATIONS - A MECHANISTIC STUDY OF THE OXIDATION CHEMISTRY OF CNRHME(3) (CN = 1,4,7-TRIMETHYL-1,4,7-TRIAZACYCLONONANE)

The trimethylrhodium(III) complex CnRhMe(3) (1, Cn = 1,4,7-trimethyl-1 ,4,7-triazacyclononane) undergoes a nearly reversible one-electron oxi dation at E degrees = -0.15 V vs Cp2Fe/Cp2Fe+ (cyclic voltammetry, 1.0 V/s) in acetonitrile/0.1 M Bu4NPF6. Preparative electrolysis as well as homogeneous oxidations with substituted ferricinium salts gives a-m ixture of CnRhMe(2)(NCMe)(+) (2) and CnRhMe(NCMe)(2)(2+) (3), the 2:3 ratio being independent of the nature of the oxidant. In addition, the reactions yielded ethane, mostly by intramolecular elimination. An in vestigation of the kinetics of the reaction of 1'+ by derivative cycli c voltammetry revealed a unimolecular reaction (Delta H+ = 57.0 +/- 0. 9 kJ/mol, Delta S-double dagger = -35.4 +/- 3.0 J/(K.mol), k(20 degree s C) = 5.9 s(-1)) with negligible solvent effects (MeCN vs CH2Cl2.). I t is proposed that 1(.+) eliminates ethane to generate the formally 15 -electron CnRhMe(.+) in the rate-determining step. The final Rh-contai ning products are likely formed from this species and 1(.+).