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Endogenous and Exogenous Ligand‐Dependent Formation of a Superoxide‐Bridged Dicobalt(III) Complex and Mononuclear Co III Complexes with Amide‐Based Macrocyclic Ligands
Author(s) -
Kumar Sushil,
Gupta Rajeev
Publication year - 2014
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.201402743
Subject(s) - chemistry , amide , ligand (biochemistry) , denticity , steric effects , stereochemistry , cobalt , medicinal chemistry , metal , superoxide , electron paramagnetic resonance , macrocyclic ligand , receptor , inorganic chemistry , organic chemistry , biochemistry , physics , nuclear magnetic resonance , enzyme
We report superoxide‐bridged dicobalt(III) complex 1 supported by 13‐membered amide‐based macrocyclic ligand H 2 L H . Complex 1 displays a sharp radical‐type EPR spectrum ( g = 2.031) and a short O–O distance (1.303 Å). Complex 1 can be synthesized by the reaction of in situ generated [Co 2+ (L H )] species with O 2 or KO 2 as well as by the reaction of (Et 4 N)[Co 3+ (L H )(Cl) 2 ] ( 2 ) with KO 2 . In contrast, analogous macrocyclic ligands carrying Cl and CH 3 substituents on the aromatic ring produced the mononuclear Co 3+ complexes [Co(L Cl )(Cl)(dmf)] ( 3 ) and [Co(L Me )(Cl)(dmf)] ( 4 ) under identical reaction conditions. Furthermore, the reaction of H 2 L H with Co(OAc) 2 yielded the mononuclear Co 3+ complex [Co(L H )(η 2 ‐OAc)] ( 5 ) with a unique bidentate acetate group and a highly distorted six‐coordinate geometry around the metal. Steric factors induced by the endogenous and exogenous ligands are believed to control the formation of the distinct cobalt complexes.