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Amidinates – Versatile Ligands for Tetravalent Actinides
Schöne, S.ORC; Kloditz, R.ORC; März, J.ORC; Kaden, P.ORC; Patzschke, M.ORC; Roesky, P. W.; Stumpf, T.
Amidinates, a group of heteroallylic nitrogen donor ligands of type [RC(NR‘)2]–, have been used in a widespread manner in coordination chemistry and organometallics. They usually coordinate in a N,N’-bidendate mode to almost all metals in the periodic table including lanthanides and early actinides. The steric and electronic properties can be easily tuned by varying the substituents R and R’ to make them a valuable class of spectator ligands.
We have expanded the rich chemistry of amidinates to the tetravalent transuranic elements Np and Pu and compared the results to the earlier actinides Th and U and other tetravalent analogues. The focus of our investigations lies in the comprehensive characterization of An(IV) complexes with amidinates, both in the solid state and in solution. A comparison within the series enables us to perform a detailed structural analysis, which is complemented by high-level quantum chemical calculations to gain deeper insight into the bonding properties of tetravalent actinides (An(IV)).
Several An(IV) amidinate complexes have been synthesized including a series of chiral complexes using the chiral benzamidine, (S,S)-N,N‘-Bis-(1-phenylethyl)-benzamidine ((S)-HPEBA) [1]. We obtained the first enantiopure amidinate complexes [AnIVCl((S)-PEBA)3] (An = Th, U, and Np) as well as the analogous Ce(IV) compound, a chemical analog of An(IV). The tris-amidinate complexes have been structurally characterized in solid state and in solution showing a comparable complex geometry.
The presence of one chloro ligand in addition to three stabilizing amidinate ligands in the An coordination sphere points to complex reactivity. This could indeed be demonstrated by reduction to homoleptic trivalent actinide amidinates [An((S)-PEBA)3] (An = U, Np) as well as halogen exchange with pseudo-halogenides (i.e. N3–).
  • Lecture (Conference)
    GdCh Fachgruppentagung Nuklearchemie, 25.09.2019, Dresden, Deutschland

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Publ.-Id: 29836