Reactions of a uranium(III) complex with N-heterocycles to form diuranium(IV) ketimides

The chemistry of the classical uranium(III) complex [U(N′′) 3 ] (N′′ = {N(SiMe 3 ) 2 } – ) is well-developed, but there have been surprisingly few studies of its reactivity towards N -heterocycles. Here we report the separate reactions of [U(N′′) 3 ] with pyrazine, 4-azido-pyridine, and the methylene transfer agent N -(9,10-dihydro-9,10-epiminoanthracen-11-yl)methanimine (C 14 H 10 N 2 CH 2 ) to give the respective diuranium(IV) products [{U(N′′) 3 } 2 (μ-NC 4 H 4 N-1κ N ,2κ N ′)] ( 1 ), [{U(N′′) 3 } 2 (μ-NC 5 H 4 N-1κ N ,2κ N ′)] ( 2 ) and [{U(N′′) 3 } 2 (m-NC 14 H 10 N-1κ N ,2κ N ′)] ( 3 ). The solid-state structures of complexes 2 and 3 respectively revealed bent U–N=C angles of 167.6(5) and 155.3(4)°, short U–N bond lengths of 2.070(5) and 2.104(4) Å, and diagnostic C=N ketimide distances of 1.297(7) and 1.364(7) Å. A combination of structural, spectroscopic, magnetic, and quantum-chemical calculations was required to confidently assign U(IV) ions exclusively in complexes 1-3 , and to prove that 2 and 3 are ketimides rather than iminyls or nitrenes. Together, this study underscores the need for comprehensive analysis for the correct interpretation of the electronic structures of actinide complexes.