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Metal‐Templated, Tight Loop Conformation of a Cys‐X‐Cys Biomimetic Assembles a Dimanganese Complex
Author(s) -
Le Trung,
Nguyen Hao,
Perez Lisa M.,
Darensbourg Donald J.,
Darensbourg Marcetta Y.
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201913259
Subject(s) - protonation , chemistry , ligand (biochemistry) , metal , crystallography , stereochemistry , zinc , nitrogen inversion , metal ions in aqueous solution , solid state , nitrogen , ion , receptor , organic chemistry , biochemistry
With the goal of generating anionic analogues to MN 2 S 2 ⋅ Mn(CO) 3 Br we introduced metallodithiolate ligands, MN 2 S 2 2− prepared from the Cys‐X‐Cys biomimetic, ema 4− ligand (ema=N,N′‐ethylenebis(mercaptoacetamide); M=Ni II , [V IV ≡O] 2+ and Fe III ) to Mn(CO) 5 Br. An unexpected, remarkably stable dimanganese product, (H 2 N 2 (CH 2 C=O(μ‐S)) 2 )[Mn(CO) 3 ] 2 resulted from loss of M originally residing in the N 2 S 2 4− pocket, replaced by protonation at the amido nitrogens, generating H 2 ema 2− . Accordingly, the ema ligand has switched its coordination mode from an N 2 S 2 4− cavity holding a single metal, to a binucleating H 2 ema 2− with bridging sulfurs and carboxamide oxygens within Mn‐μ‐S‐CH 2 ‐C‐O, 5‐membered rings. In situ metal‐templating by zinc ions gives quantitative yields of the Mn 2 product. By computational studies we compared the conformations of “linear” ema 4− to ema 4− frozen in the “tight‐loop” around single metals, and to the “looser” fold possible for H 2 ema 2− that is the optimal arrangement for binucleation. XRD molecular structures show extensive H‐bonding at the amido‐nitrogen protons in the solid state.