Promoting a non-heme manganese complex catalyzed oxygen transfer reaction by both lewis acid and Brønsted acid: Similarities and distinctions.

[Display omitted] • Lewis and Brønsted acids can sharply improve the oxygen transfer efficiency of a manganese(II) catalyst with non-heme ligand. • The catalytic activity improvement is acidity strength or net charge dependent. • The promotional effect by either Lewis acid or Brønsted acid was originated from the dissociating sluggish di-μ-oxo core. • Distinctions of reactive intermediate were also demonstrated for Lewis acid or Brønsted acid. This work demonstrates that certain Lewis and Brønsted acids can sharply improve the oxygen transfer efficiency of a manganese(II) catalyst bearing non-heme ligand. In the absence of Lewis and Brønsted acids, oxidation of manganese(II) complex will generate di-μ-oxo-bridged dinuclear Mn 2 (III,IV) core which is very sluggish for olefin epoxidation. Adding non-redox metal ions as Lewis acid or Brønsted acid will both improve the catalytic epoxidation of olefin, and this improvement is dependent on the pK a of Brønsted acid, or the net charge of non-redox metals of Lewis acid. Mechanism study revealed that similar promotional effect by either Lewis or Brønsted acids was originated from a similar reaction pathway by dissociating aforementioned sluggish di-μ-oxo core. However, distinctions of reactive intermediate were also demonstrated for Lewis or Brønsted acids. [ABSTRACT FROM AUTHOR]