Cage-like manganesesilsesquioxanes: features of their synthesis, unique structure, and catalytic activity in oxidative amidations

Abstract

An extended series of Mn-based cage-like phenylsilsesquioxanes were obtained via convenient self-assembly reactions and complexations with 1,10-phenanthroline. The structural features of these cage complexes such as (i) various nuclearities and types of silsesquioxane ligands, (ii) encapsulations of hydroxide and chloride species, and (iii) spontaneous oxidations of Mn^II to Mn^III are established by single-crystal X-ray diffraction, including the use of synchrotron radiation. One of the synthesized compounds represents a unique feature among metallacomplexes – the presence of three metal ions with different oxidation states (Na^I, Mn^II, and Mn^III). Furthermore, the first-ever evaluation of Mn–silsesquioxanes as precatalysts in oxidative amidation (OA) reactions allowed us to develop a very effective protocol of OA of alcohols and aldehydes with low loading of Mn (5 mol% and 2.5 mol%, respectively).