Gas-Phase C−H and N−H Bond Activation by a High Valent Nitrido-Iron Dication and 〈NH〉-Transfer to Activated Olefins

A tetrapodal pentadentate nitrogen ligand (2,6-bis(1,1-di(aminomethyl)ethyl)pyridine, <b>1</b>) is used for the synthesis of the azido-iron(III) complex [(<b>1</b>)Fe(N₃)]X₂ where X is either Br or PF₆. By means of electrospray ionization mass spectrometry, the dication [(<b>1</b>)Fe(N₃)]²⁺ can be transferred into the gas phase as an intact entity. Upon collisional activation, [(<b>1</b>)Fe(N₃)]²⁺ undergoes an expulsion of molecular nitrogen to afford the dicationic nitrido-iron species [(<b>1</b>)FeN]²⁺ as an intermediate, which upon further activation can intramolecularly activate C−H− and N−H bonds of the chelating ligand <b>1</b> or can transfer an 〈NH〉 unit in bimolecular reactions with activated olefins. The precursor dication [(<b>1</b>)Fe(N₃)]²⁺, the resulting nitrido species [(<b>1</b>)FeN]²⁺, and its possible isomers are investigated by mass spectrometric experiments, isotopic labeling, and complementary computational studies using density functional theory.