Synthesis and characterization of pn monoanionic ligands and their reactivity with actinides

Abstract

Organoactinide complexes have gained much popularity in the recent decades particularly in the field of nuclear waste sequestration. With the increase of nuclear power along side other residual nuclear waste from power plants and testing and use of nuclear bombs, there has been a rapid increase in actinides in the environment. In an effort to sequester and separate actinides form other radioactive elements in the waste, understanding the unique reactivity of the actinides has been key. Actinides and lanthanides make up the f-block in the periodic table meaning they contain f-orbital which effects its ligand bonding making their interaction more electrostatic versus covalent typically seen in d-block transition metals. The added radioactive properties also plays a role in its environmental safety and half-life of the various elements in the actinide series. Utilizing already existing concepts and properties such as HSAB and the Relativistic Effects, have helped develop new ligands in the effort to further understand the reactivity of actinides and how it differs from other radio toxins. In collaboration with Stephan Hohloch at the University of Innsbruck our group developed a new preliminary organoactinide complex, NP-Th containing the ligand (N-(2-(diisopropylphosphanyl)-4-methylphenyl)-2,4,6-trimethylanilide, short NP). The NP ligand has been extensively studied in its reactivity with lanthanide metals producing numerous organolathanide complexes containing either one or two NP ligands. Thus far the only NP-actinide complex reported has been with uranium as observed in 2018 by Schelter and Mindiola et al. With the introduction of the preliminary NP-Th complex comparisons between the two organoactinide complexes can be determined. In addition, a novel PN ligand was synthesized utilizing a phosphorous anionic center; [(TrippPH)-2-(C6H4)N(Me2)], short as PN;- bold shows the anionic reactivity site; Tipp = 2,4,6- iPr3C6H2. Since the synthesis of the PN ligand required an intermediate complex, its precursor was also reported, [(TrippPCl)-2-(C6H4)N(Me2)], along with its arsenic analogue; abbreviated as EN-Cl (E=P, As). Nuclear magnetic resonance (1H, 13C, and 31P) techniques were used in characterizing the purity of the NP-Th complex and the novel PN ligand and its precursor EN. The reactivity of the PN with any f-block metals have yet to be determined.