Isolation and characterization of the elusive cyanoformate ion and the dependence of its stability on solvent dielectric constant

Abstract

The cyanoformate ion, speculated to be an intermediate by-product in the biosynthesis of ethylene in plants for decades but never observed, was successfully isolated for the first time as its tetraphenylphosphonium salt ([PPh[subscript 4]][NCCO[subscript 2]]). Full spectroscopic and crystallographic characterization of [PPh[subscript 4]][NCCO[subscript 2]] is provided, including characterization of [superscript 13]C-labelled isotopologues. In situ infrared spectroscopic analysis of the decomposition of cyanoformate in various solvents has revealed that cyanoformate will dissociate into CN- and CO[subscript 2] in higher dielectric media. The active site of 1-aminocyclopropane-1-carboxylic acid oxidase (ACC oxidase) bears an iron atom which may be protected from produced cyanide by its complexation with CO[subscript 2] as cyanoformate. When cyanoformate migrates out of the active site of the enzyme to the higher dielectric cytosol, it then dissociates, producing CN[superscript -] or HCN, which is subsequently metabolized.