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N 2 O Reductase Activity of a [Cu 4 S] Cluster in the 4Cu I Redox State Modulated by Hydrogen Bond Donors and Proton Relays in the Secondary Coordination Sphere
Author(s) -
Hsu ChiaWei,
Rathnayaka Suresh C.,
Islam Shahidul M.,
MacMillan Samantha N.,
Mankad Neal P.
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201906327
Subject(s) - chemistry , deprotonation , nitrous oxide reductase , coordination sphere , reactivity (psychology) , hydrogen bond , redox , crystallography , stereochemistry , active site , catalysis , inorganic chemistry , crystal structure , molecule , ion , enzyme , organic chemistry , nitrite reductase , medicine , alternative medicine , nitrate reductase , pathology
The model complex [Cu 4 (μ 4 ‐S)(dppa) 4 ] 2+ ( 1 , dppa=μ 2 ‐(Ph 2 P) 2 NH) has N 2 O reductase activity in methanol solvent, mediating 2 H + /2 e − reduction of N 2 O to N 2 +H 2 O in the presence of an exogenous electron donor (CoCp 2 ). A stoichiometric product with two deprotonated dppa ligands was characterized, indicating a key role of second‐sphere N−H residues as proton donors during N 2 O reduction. The activity of 1 towards N 2 O was suppressed in solvents that are unable to provide hydrogen bonding to the second‐sphere N−H groups. Structural and computational data indicate that second‐sphere hydrogen bonding induces structural distortion of the [Cu 4 S] active site, accessing a strained geometry with enhanced reactivity due to localization of electron density along a dicopper edge site. The behavior of 1 mimics aspects of the Cu Z catalytic site of nitrous oxide reductase: activity in the 4Cu I :1S redox state, use of a second‐sphere proton donor, and reactivity dependence on both primary and secondary sphere effects.