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.