Lewis Acid Activation of the Ferrous Heme–NO Fragment toward the N–N Coupling Reaction with NO To Generate N2O

• DOI: 10.1021/jacs.7b13681
• Publication Date: 2018-03-04T14:13:07Z
• Authors: Erwin G. Abucayon; Rahul L. Khade; Douglas R. Powell; Yong Zhang; George B. Richter...
• Keywords: Nitrous Oxide; Quantum Theory; Ferrous Compounds; Heme; Nitric Oxide; 01 natural sciences; Lewis Acids; 0104 chemical sciences

Bacterial NO reductase (bacNOR) enzymes utilize a heme/non-heme active site to couple two NO molecules to N2O. We show that BF3 coordination to the nitrosyl O-atom in (OEP)Fe(NO) activates it toward N-N bond formation with NO to generate N2O. 15N-isotopic labeling reveals a reversible nitrosyl exchange reaction and follow-up N-O bond cleavage in the N2O formation step. Other Lewis acids (B(C6F5)3 and K+) also promote the NO coupling reaction with (OEP)Fe(NO). These results, complemented by DFT calculations, provide experimental support for the cis: b3 pathway in bacNOR.