Spectroscopic and Theoretical Insights into H₂ Activation on Uranium Monoxide: Homolytic H₂ Cleavage Mediated by Intermediate OU(η²-H₂)

Abstract

Elucidating molecular-level interactions between dihydrogen (H 2 ) and uranium oxides reveals fundamental insights into the intrinsic H 2 activation mechanisms underlying processes such as heterogeneous catalysis over uranium oxides and corrosion of uranium induced by H 2 . Herein, the reactions of H 2 with uranium monoxide (UO) molecules have been investigated via a combination of matrix-isolation infrared spectroscopy and quantum chemical calculations. A side-on bonded H 2 complex, OU(η 2 -H 2 ), is identified at 3733.7 and 800.3 cm −1 . This species is regarded as a crucial intermediate along H 2 activation pathways. Bonding analysis reveals cooperative U(π 5f/6d ) → H 2 (σ*) π // backdonation and U ← H 2 (σ) σ donation in OU(η 2 -H 2 ) that facilitate the activation of the H 2 moiety. Upon λ > 550 nm photoirradiation, OU(η 2 -H 2 ) isomerizes into H 2 UO, indicating the homolytic H 2 cleavage on UO. Mechanistic details of H 2 adsorption and dissociation on UO molecules have been further elucidated.