Stephen T. Liddle

We report the synthesis and characterisation of thorium(IV), uranium(III), and uranium(IV) complexes supported by a sterically demanding triamidoamine ligand with N ‐diphenyl‐ tert ‐butyl‐silyl substituents. Treatment of ThCl 4 (THF) 3.5 or UCl 4 with [Li 3 (Tren DPBS )] (Tren DPBS ={N(CH 2 CH 2 NSiPh 2 Bu t ) 3 } 3− ) afforded [An(Tren DPBS )Cl] (An=Th, 1Th ; U, 1U ). Complexes 1An react with benzyl potassium to afford the cyclometallates (Tren DPBS cyclomet ) [An{N(CH 2 CH 2 NSiPh 2 Bu t ) 2 (CH 2 CH 2 NSiPhBu t C 6 H 4 )}] (An=Th, 2Th ; U, 2U ). Treatment of 1An with sodium azide affords [An(Tren DPBS )N 3 ] (An=Th, 3Th ; U, 3U ). Reaction of 3Th with potassium graphite affords 2Th . In contrast, 3Th reacts with cesium graphite to afford the doubly‐cyclometallated (Tren DPBS d‐cyclomet ) ate complex [Th{N(CH 2 CH 2 NSiPh 2 Bu t )(CH 2 CH 2 NSiPhBu t C 6 H 4 )} 2 Cs(THF) 3 ] ( 4 ). In contrast to 3Th , reaction of 3U with potassium graphite produces the uranium(III) complex [U(Tren DPBS )] ( 5 ), and 5 can also be prepared by reaction of potassium graphite with 1U . The loss of azide instead of conversion to nitrides contrasts to prior work when the silyl group is iso ‐propyl silyl, underscoring how ligand substituents profoundly drive the reaction chemistry. Several complexes exhibit T‐shaped meta ‐C−H⋅⋅⋅phenyl and staggered parallel π–π‐stacking interactions, demonstrating subtle weak interactions that drive ancillary ligand geometries. Compounds 1An – 3An , 4 , and 5 have been variously characterised by single crystal X‐ray diffraction, multi‐nuclear NMR spectroscopy, infrared spectroscopy, UV/Vis/NIR spectroscopy, and elemental analyses.