Nitric oxide generation from nitrate at the cobalt center

Abstract

Herein, we report the synthesis and reactivity of the cobalt(II) nitrate complex, ( ^acri PNP)Co(NO ₃ ) ( 2 ). Exposure of 2 to both CO(g) or PPh ₃ drives a deoxygenation pathway to afford the mononitrosyl nitrite cobalt species ( 4 ). To elucidate the electronic features of this transformation, the 4‐coordinate cationic cobalt nitrosyl species ( 5 ) was independently prepared. Although both 4 and 5 possess an identical {CoNO} ⁸ core, both species exhibit remarkably distinct NO characters: square‐planar 5 displays a linear NO ⁺ character (ν _NO  = 1826 cm ⁻¹ ), whereas square‐pyramidal 4 shows a bent, apical NO binding with a nitrosyl vibration at 1655 cm ⁻¹ . Furthermore, chemical reduction of 5 induces an intricate {CoNO} ⁹ generation and NO disproportionation cascade that ultimately converges to form 4. These findings demonstrate that the ( ^acri PNP)Co scaffold offers electronic flexibility for governing coordination environment and redox pathways in NO _x interconversion.