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Manganese Complexes of Pyrrole‐ and Indolecarboxamide Ligands: Synthesis, Structure, Electrochemistry, and Applications in Oxidative and Lewis‐Acid‐Assisted Catalysis
Author(s) -
Yadav Sunil,
Kumar Sushil,
Gupta Rajeev
Publication year - 2015
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201500773
Subject(s) - chemistry , catalysis , ligand (biochemistry) , lewis acids and bases , nucleophile , pyrrole , manganese , electrochemistry , redox , coordination sphere , ring (chemistry) , olefin fiber , medicinal chemistry , coordination complex , photochemistry , inorganic chemistry , polymer chemistry , crystallography , organic chemistry , metal , crystal structure , biochemistry , receptor , electrode
Abstract This work shows the synthesis and structural, spectroscopic, and electrochemical properties of Mn III complexes supported with pyrrole‐ and indolecarboxamide ligands. In all cases, the respective ligand constitutes a N 4 coordination sphere about the Mn III ion. The Mn III 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 Mn III/II and moderately positive Mn IV/III redox potentials. In situ generated Mn 4+ 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, Mn III complexes carrying electron‐donating substituents on the ligand were found to be better catalysts.