Synthesis of a heterobimetallic actinide nitride and an analysis of its bonding.

Reaction of [K(DME)][Th{ N (R)(SiMe 2 C H 2 )} 2 (NR 2 )] (R = SiMe 3 ) with 1 equiv. of [U(NR 2 ) 3 (NH 2 )] (1) in THF, in the presence of 18-crown-6, results in formation of a bridged uranium-thorium nitride complex, [K(18-crown-6)(THF) 2 ][(NR 2 ) 3 U IV (μ-N)Th IV (NR 2 ) 3 ] (2), which can be isolated in 48% yield after work-up. Complex 2 is the first isolable molecular mixed-actinide nitride complex. Also formed in the reaction is the methylene-bridged mixed-actinide nitride, [K(18-crown-6)][K(18-crown-6)(Et 2 O) 2 ][(NR 2 ) 2 U(μ-N)(μ-κ 2 - C , N -CH 2 SiMe 2 NR)Th(NR 2 ) 2 ] 2 (3), which can be isolated in 34% yield after work-up. Complex 3 is likely generated by deprotonation of a methyl group in 2 by [NR 2 ] - , yielding the new μ-CH 2 moiety and HNR 2 . Reaction of 2 with 0.5 equiv. of I 2 results in formation of a U V /Th IV bridged nitride, [(NR 2 ) 3 U V (μ-N)Th IV (NR 2 ) 3 ] (4), which can be isolated in 42% yield after work-up. The electronic structure of 4 was analyzed with EPR spectroscopy, SQUID magnetometry, and NIR-visible spectroscopy. This analysis demonstrated that the energies of 5f orbitals of 4 are largely determined by the strong ligand field exerted by the nitride ligand.