Synthesis, characterization and electrochemistry of bis(3-aryl-6,6-dimethylcyclohexadienyl)ruthenium complexes
摘要:
Five bis(3-aryl-6,6-dimethylcyclohexadienyl)ruthenium complexes (4a-4e) are prepared by reactions between di-mu-chlorodichlorobis[(1-3 eta:6-8 eta)-2,7-dimethyl-octadienyl]diruthenium and the corresponding dienes. The larger aryl substituents increase the barrier to rotation in 4a-4e relative to bis(3-methyl-6,6-cyclohexadienyl) ruthenium (5b). The activation parameters were determined by line-shape analysis for the exchange process in 4a: Delta G(dagger) (183 K), 8.0 +/- 0.2 kcal/mol; Delta H-dagger, 10.3 kcal/mol; and Delta S-dagger, 13 cal/mol/K. The electronic effect of the aryl substituents on the cyclohexadienyl ligand on the oxidation potential of the complex are compared to the effect of methyl substituents. (c) 2006 Elsevier B.V. All rights reserved.