Manganese Complexes of Pyrrole‐ and ­Indolecarboxamide Ligands: Synthesis, Structure, Electrochemistry, and Applications in Oxidative and Lewis‐Acid‐­Assisted Catalysis

Abstract

This work shows the synthesis and structural, spectroscopic, and electrochemical properties of MnIII complexes supported with pyrrole‐ and indolecarboxamide ligands. In all cases, the respective ligand constitutes a N4 coordination sphere about the MnIII ion. The MnIII complexes of pyrrolecarboxamide ligands are square pyramidal with a fifth Cl atom, whereas analogous complexes of indolecarboxamide ligands are essentially square planar. Electrochemical studies reveal highly negative MnIII/II and moderately positive MnIV/III redox potentials. In situ generated Mn4+ species of the pyrrolecarboxamide ligands were characterized by absorption and electron paramagnetic resonance spectroscopy. All complexes functioned as catalysts in olefin epoxidation reactions by using PhIO as the oxo‐transfer agent. All complexes also acted as Lewis acid catalysts for ring‐opening reactions of assorted epoxides with various nucleophiles. We also show a one‐pot, two‐step epoxidation reaction followed by ring opening, which illustrates the catalytic significance of the present complexes. Importantly, MnIII complexes carrying electron‐donating substituents on the ligand were found to be better catalysts.

In situ preparation of a ferric polymeric aluminum chloride–silica gel nanocatalyst by mechanical grinding and its solid-phase catalytic behavior in organic synthesis

“…Four classes of nitrogen-containing compounds such as 3alkylindole derivatives, 21,22 quinoxaline derivatives, 23,24 benzimidazole derivatives, 25,26 and b-amino alcohol derivatives 27,28 are widely used in the synthesis of pharmaceutical intermediates. The research on the green and efficient synthesis of these products from simple chemical raw materials has great practical value, and the use of mechanochemical methods to produce the above compounds will greatly reduce the generation of toxic waste during the production process.…”

Recent Trends and Prospects in Homogeneous Manganese‐Catalysed Epoxidation

“…A well characterized series of Mn III ‐complexes with pyrrole and indolecarboxamide ligands has been used in the catalytic epoxidation of alkenes using PhIO as oxidant [40] . They found that the Mn‐complexes with electron‐donating groups on the ligand (methyl group) showed enhanced catalytic potential (Scheme 21).…”

“…A well characterized series of Mn III -complexes with pyrrole and indolecarboxamide ligands has been used in the catalytic epoxidation of alkenes using PhIO as oxidant. [40] They found that the Mn-complexes with electron-donating groups on the ligand (methyl group) showed enhanced catalytic potential (Scheme 21). Moreover, they observed better reactivity with aromatic alkenes when compared with aliphatic alkenes and among aromatic alkenes, one with electron donating groups at para-position afforded higher yields.…”

Bronzemedaillen der CRSI: P. S. Mukherjee, D. B. Ramachary, T. Govindaraju und R. Gupta / SwarnaJayanti‐Stipendien: S. Ghosh und C. M. Reddy / Albrecht‐Kossel‐Preis: J. Buchner / Nachwuchswissenschaftler‐Preis der DECHEMA: T. A. M. Gulder / Mattauch‐Herzog‐Preis: K. Pagel / Ehrendoktorwürden: F. Schüth und T. J. Marks / Karl‐Max‐von‐Bauernfeind‐Medaille: C. W. Kohlpaintner

“…Nach einem Postdoktorat bei Andy S. Borovik an der University of Kansas begann er 2003 an der University of Delhi mit seiner unabhängigen Forschung. Er interessiert sich für das Design geordneter Materialien aus Koordinationsverbindungen und hat im European Journal of Inorganic Chemistry Mangankomplexe mit Pyrrol‐ und Indolcarboxamidliganden vorgestellt …”