Cleavage of Dinitrogen from Forming Gas by a Titanium Molecular System under Ambient Conditions

Chemistry. 2017 Mar 13;23(15):3558-3561. doi: 10.1002/chem.201700152. Epub 2017 Feb 20.

Abstract

Simple exposure of a hexane solution of [TiCp*Me3 ] (Cp*=η5 -C5 Me5 ) to an atmosphere of commercially available and inexpensive forming gas (H2 /N2 mixture, 13.5-16.5 % of H2 ) at room temperature leads to the methylidene-methylidyne-nitrido cube-type complex [(TiCp*)4 (μ3 -CH)(μ3 -CH2 )(μ3 -N)2 ] via dinitrogen cleavage. This paramagnetic compound reacts with [D1 ]chloroform to give the titanium(IV) methylidyne-nitrido species [(TiCp*)4 (μ3 -CH)2 (μ3 -N)2 ], whereas its one-electron oxidation with AgOTf or [Fe(η5 -C5 H5 )2 ](OTf) (OTf=O3 SCF3 ) yields the diamagnetic ionic derivative [(TiCp*)4 (μ3 -CH)(μ3 -CH2 )(μ3 -N)2 ](OTf). The μ3 -nitrido ligands of the methylidyne-nitrido cubane complex can be protonated with [LutH](OTf) (Lut=2,6-lutidine) or hydrogenated with NH3 ⋅BH3 to afford μ3 -NH imido moieties.

Keywords: cage compounds; methylidyne ligands; nitrides; nitrogen fixation; titanium.