Tantalum Ureate Complexes for Photocatalytic Hydroaminoalkylation

Using a tantalum ureate pre-catalyst, photocatalytic hydroaminoalkylation of unactivated alkenes with unprotected amines at room temperature is demonstrated. The combination of Ta(CH2SiMe3)3Cl2 and a ureate ligand with a saturated cyclic backbone resulted in this unique reactivity. Preliminary investigations of the reaction mechanism suggest that both the thermal and photocatalytic hydroaminoalkylation reactions begin with N–H bond activation and subsequent metallaaziridine formation. However, a select tantalum ureate complex, through ligand to metal charge transfer (LMCT), results in photocatalyzed homolytic metal–carbon bond cleavage and subsequent addition to unactivated alkene to afford the desired carbon–carbon bond formation. Origins of ligand effects on promoting homolytic metal–carbon bond cleavage are explored computationally to support enhanced ligand design efforts.