cis-Dihydroxylation and Epoxidation of Alkenes by [Mn2O(RCO2)2(tmtacn)2]:  Tailoring the Selectivity of a Highly H2O2-Efficient Catalyst

• Published in: Journal of the American Chemical Society 2005-06, Vol.127 (22), p.7990-7991
• Main Authors: de Boer, Johannes W., Brinksma, Jelle, Browne, Wesley R., Meetsma, Auke, Alsters, Paul L., Hage, Ronald, Feringa, Ben L.
• Format: Article
• Language: English
• Subjects: Chemical reactivity; Chemistry; Exact sciences and technology; Organic chemistry; Reactivity and mechanisms
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja050990u

The carboxylic acid promoted cis-dihydroxylation and epoxidation of alkenes catalyzed by [MnIV 2O3(tmtacn)2]2+ 1 employing H2O2 as oxidant is described. The use of carboxylic acids at cocatalytic levels not only is effective in suppressing the inherent catalase activity of 1, but also enables the tuning of the catalyst's selectivity. Spectroscopic studies and X-ray analysis confirm that the control arises from the in situ formation of carboxylate-bridged dinuclear complexes, for example, 2 {[MnIII 2O(CCl3CO2)2(tmtacn)2]2+} and 3 {[MnII 2(OH)(CCl3CO2)2(tmtacn)2]+}, during catalysis. For the first time, the possibility to tune, through the carboxylate ligands employed, both the selectivity and activity of dinuclear Mn-based catalysts is demonstrated. To our knowledge, the system 1/2,6-dichlorobenzoic acid (up to 2000 turnover numbers for cis-cyclooctanediol) is the most active Os-free cis-dihydroxylation catalyst reported to date.