Activation of Ligand Reaction on an Iron Complex: H/D Exchange Reaction of a Low-Spin Bis[2-(Pyridylmethylidene)-1-(2-pyridyl)methylamine]iron(II) Complex

Abstract

With the aim of shedding some light on the still scarcely investigated mechanism of transformation of imines in metal complexes, this study describes the investigation of the hydrogen–deuterium (H/D) exchange reaction of a bis[2-(pyridylmethylidene)-1-(2-pyridylmethylamine]iron(II) complex ([Fe(PMAP)₂]²⁺), following our previous work on a low-spin iron(II) complex bearing two molecules of S-2-pyridylmethylidene-1-(2-pyridyl)ethylamine. This complex has been proven to undergo successive transiminations in acetonitrile, yielding a bis[1-(2-pyridyl)ethylidene-2-pyridylmethylamine]iron(II) complex. In the analogous [Fe(PMAP)₂]²⁺ complex, a 1,3-hydrogen rearrangement occurs in a 10% deuterium oxide-acetonitrile-d₃ (D₂O–CD₃CN) solution. The H/D exchange reaction of [Fe(PMAP)₂]²⁺ was examined in the presence of various concentrations of 2,6-dimethylpyridine as a base in a 10% D₂O–CD₃CN solution at 45 °C, and the reaction mechanism was investigated.

Graphical Abstract