Modeling Reactivity of Nitrite and Nitrous Acid at a Phenolate Bridged Dizinc(II) Site: Insights into NO Signaling at Zinc
Gayathri Kolliyedath, Taraknath Chattopadhyay, Aditesh Mondal, Aiswarya Panangattu, Girish Muralikrishnan, Subrata Kundu
Abstract
Abstract Although nitrite‐to‐NO transformation at various transition metals including Fe and Cu are relatively well explored, examples of such a reaction at the redox‐inactive zinc(II) site are limited. The present report aims to gain insights into the reactivity of nitrite anions, nitrous acid (HONO), and organonitrite (RONO) at a dizinc(II) site. A phenolate‐bridged dizinc(II)‐aqua complex [ L H Zn II (OH 2 )] 2 (ClO 4 ) 2 ( 1 H ‐Aq , where L H =tridentate N,N,O‐donor monoanionic ligand) is illustrated to react with t BuONO to provide a metastable arene‐nitrosonium charge‐transfer complex 2 H . UV‐vis, FTIR, multinuclear NMR, and elemental analyses suggests the presence of a 2 : 1 arene‐nitrosonium moiety. Furthermore, the reactivity of a structurally characterized zinc(II)‐nitrite complex [ L H Zn II (ONO)] 2 ( 1 H ‐ONO ) with a proton‐source demonstrates HONO reactivity at the dizinc(II) site. Reactivity of both RONO (R=alkyl/H) at the phenolate‐bridged dizinc(II) site provides NO + charge‐transfer complex 2 H . Subsequently, the reactions of 2 H with exogenous reductants (such as ferrocene, thiol, phenol, and catechol) have been illustrated to generate NO. In addition, NO yielding reactivity of [ L H Zn II (ONO)] 2 ( 1 H ‐ONO ) in the presence of the above‐mentioned reductants have been compared with the reactions of complex 2 H . Thus, this report sheds light on the transformations of NO 2 − /RONO (R=alkyl/H) to NO/NO + at the redox‐inactive zinc(II) coordination motif.