Iron(III) Complexes with Cross-Bridged Cyclams: Synthesis and Use in Alcohol and Water Oxidation Catalysis

A class of iron(III) complexes containing diversely substituted cross-bridged cyclams (1-R,R': 1-Me,Me, 1-Me,Et, 1-Et,Et, 1-Me,Bn, 1-Bn,Bn) has been prepared and characterized. (1-R,R') complexes catalyze the oxidation of alcohols to ketones in green conditions, by using tert-butylhydroperoxide as the oxidant in aqueous solutions. They also exhibit catalytic activity in water oxidation (WO) to molecular oxygen driven by NaIO4, and the results were found to be dependent on the steric hindrance of the R-substituents. Best compromise in terms of accessibility and protection of the metal center was obtained with 1-Me,Et (TOF = 1.4 min(-1) and TON = 111).