Synthesis and Catalytic Activity of Thorium Nitride Complex from Dinitrogen Reduction

Metal nitride species are recognized as key intermediates in the conversion of dinitrogen (N₂) to ammonia (NH₃). In this work, we report the isolation of a multimetallic nitride-bridged thorium complex (2) by completely cleaving the N≡N triple bond of N₂. The complex was synthesized through the reduction of a thorium precursor, {N[CH₂CH₂N–PⁱPr₂]₃ThCl}₂ (1) and chromium dichloride (CrCl₂) using potassium graphite (KC₈) under an N₂ atmosphere. Isotopic labeling with ¹⁵N₂ confirms that the nitride in complex 2 originates from N₂. Under ambient conditions, complex 2 exhibits remarkable catalytic activity, converting N₂ to silylamine with yields of up to 9.9 equiv per thorium molecular catalyst. This work not only represents the first isolation of a thorium nitride complex from N₂ reduction but also provides a rare example of N₂ functionalization promoted by an actinide catalyst.