Aaron Tondreau

A geometrically flexible bifunctional (bis)aminophosphine ligand was synthesized in a three-component, one-pot Kabachnik-Fields reaction using butylphosphine, paraformaldehyde, and 3,5-dimethyl aniline. The product, bis((3,5-dimethylphenyl)aminomethyl) butylphosphine ( BiAMP ), containing two secondary amines and a tertiary phosphine, was isolated in good yields. Deprotonation of both N-H groups with (trimethylsilyl)methylpotassium (K-CH SiMe ), followed by salt metathesis with LaI , YI , and LuI generated the corresponding MI( BiAMP )(thf) complexes (M = Y (1), La (2), and Lu (3)) in good yields. A sterically encumbered indene, 1,3-diisopropyl-4,7-dimethyl-1 -indene, Ind, was deprotonated and installed salt-metathesis to generate the organometallic series of η -indenide complexes, M( BiAMP )(η Ind)(thf) (M = Y (4), La (5), and Lu (6)). H, P, C, and Y NMR experiments, IR spectroscopy, and single crystal X-ray diffraction (SC-XRD), were used to characterize these complexes. The Y-P coupling constant was found to be variable depending on the modifiable coordination environment of the metal center, indicating potential as both a spectroscopic handle as well as providing insight into the influence of additional ligands on the metal center.

Development of new synthetic methods to employ with transuranium organometallic complexes will help further the field and may provide a stronger understanding of their distinct reactivity, electronic structures, and chemical bonding. Although the organoneptunium field has grown over the last decade, just a handful of complexes have been synthesized, most of which are found in the trivalent oxidation state. Few reactions with neptunium (Np) have considered the stereochemical outcome, thus we employed a diastereoselective template protocol to synthesize meso (or: C-2) complexes of neptunium(iv). Following previous success with the diastereoselective synthesis of ((ONO)-O-(tBu2P))UCl2(dtbpy) (1), adaptation to NpCl4(dme)(2) led to the isolation of diastereopure ((ONO)-O-(tBu2P))NpCl2(dtbpy) (2), ((ONO)-O-(tBu2P) = 2,6-bis((di-tert-butylphosphino)-methanolato)pyridine). The addition of a bulky indenide ligand, derived from the in situ deprotonation of 4,7-dimethyl-1,3-bis(1-methylethyl)-1H-indene (1,3-(Pr-i)(2)-4,7-Me-2-C9H3), was pursued to synthesize the organoactinide complexes ((ONO)-O-(tBu2P))U(1,3-(Pr-i)(2)-4,7-Me-2-C9H3)Cl (3) and ((ONO)-O-(tBu2P))Np(1,3-(Pr-i)(2)-4,7-Me-2-C9H3)Cl (4). Bonding analyses consisting of orbital localization and energy decomposition methods show resemblances in covalent character between uranium (1 and 3) and neptunium (2 and 4) systems. However, an increased orbital overlap was identified in the metal - indenide with respect to the metal-dtbpy interaction, mainly driven by 5f electrons. This was attributed to the better symmetry match between the organic ligand and metal orbitals that allowed the participation of the 5f orbitals.

A series of U(IV) complexes bearing alkyl and chloride ligands in the trans configuration was synthesized and characterized. Starting with the diastereopure U(IV) trans-dichloride complex meso-((ONO)-O-tBu2P)UCl2(dtbpy) (1, (ONO)-O-tBu2P = 2,6-bis((di-tert-butylphosphino)methanolato)pyridine), four distinct alkyl groups were employed to prepare ((ONO)-O-tBu2P)U(R)Cl(dtbpy), where R = (trimethylsilyl)methyl (neosilyl), 2a, R = 2,2-dimethyl propyl (neopentyl), 2b, and R = 2-methyl-2-phenyl propyl (neophyl), 2c. Alkylation occurs with specificity but generates a predominant species and a minor species corresponding to anti/syn regioisomers relative to the P-tBu2 groups of the ligand. For synthesis using R = methyl, the dimethyl complex ((ONO)-O-tBu2P)U(Me)(2)(dtbpy), 2d, was prepared; the addition of 1 equiv of MeLi produced a mixture of products. Complexes 2a-2d were characterized using single crystal X-ray diffraction (SC-XRD), UV-vis-nIR, and H-1 and P-31 NMR spectroscopies.

Related BAP [BAP = bis­(acyl)­phosphide] and Acac (Acac = β-diketonate) molecules perform as robust supports for both lanthanide and actinide metals. Here, a molecular bimetallic Eu2+ complex was successfully targeted and isolated by employing sodium bis­(mesitoyl)­phosphide [Na­(mesBAP)] in a salt metathesis with EuI2, producing [Eu­( mes BAP) 2 (et 2 o)] 2 (et2o = metal-coordinated diethyl ether). The corresponding Acac-Eu2+ complex was targeted using mesAcac– (1,3-dimesityl-1,3-propanedione), generating [Eu­( mes Acac) 2 (et 2 o)] 2 . Both complexes were characterized by single-crystal X-ray diffraction, UV–vis, IR, and NMR spectroscopies, and variable-temperature magnetic susceptibility. [Eu­( mes BAP) 2 (et 2 o)] 2 was persistent under anaerobic, anhydrous conditions, whereas the analogous [Eu­( mes Acac) 2 (et 2 o)] 2 showed evidence of decomposition under identical conditions. Variable-temperature magnetic susceptibility and magnetization studies of [Eu­( mes BAP) 2 (et 2 o)] 2 and [Eu­( mes Acac) 2 (et 2 o)] 2 were performed, resulting in similar magnetic exchange coupling values of J ex = −0.018 and −0.023 cm–1 and axial zero-field-splitting D values of −0.38 and −0.51 cm–1, respectively.

We report the synthesis and characterization of substituted aryldimethylsilyldiisopropylanilide ligands and their respective bisamido complexes of U(III), (3,5-R-2-PhMe(2)SiNDipp)(2)UI(dioxane)(x) (1, R = H, x= 0; 2, R = Me, x = 0; 3, R = Bu-t, x = 1). We found that the steric bulk of the 3,5-R-2-Ph ring affects the hapticity of the U-arene interaction. In the solid-state, 1 is a U-(eta(6)-arene) complex, while 2 is a bis(U-(eta(1)-arene)) complex. Theoretically calculated bond orders at PBE0 and PBE0-D3 levels of theory support these hapticity assignments. The 3,5-Bu-t(2)-Ph rings of 3 are too bulky to interact with U and solid-state metrical parameters initially suggested a U-(eta(1)-arene) interaction with one of the Dipp rings. However, bond order calculations show that this interaction is even weaker than in the previously reported ((PhMe2Si)(2)N)(3)U complex, leading to the conclusion that 3 is best described as a U-(eta(0)-arene) complex. Molecular orbital analyses in conjunction with electron localization methods reveal that the U-(eta(6)-arene) bonding in 1 is primarily electrostatic in nature. Some charge transfer takes place from the arene pi orbitals to the U 6d/5f hybrid orbitals in addition to subtle delta-back-bonding. In 2 and 3, both pi and delta interactions are substantially weaker, in agreement with the differences in the U-arene coordination modes. Surprisingly, attempts to generate less sterically bulky (3,5-R-2-PhMe2SiNPh)(2)UI complexes results in disproportionation to homoleptic tetraamido (3,5-R-2-PhMe2SiNPh)(4)U(IV) (4, R = H; 5, R = Me) complexes.

Organophosphorus (OP) nerve agents are a group of lethal small molecules. Fieldable detection of nerve agents is an on-going challenge that typically relies on mass spectrometry and infrared spectroscopy but not nuclear magnetic resonance (NMR) spectroscopy because of the portability limitations of superconducting magnets. However, Earth's field NMR (EFNMR) demonstrates a unique signature space for OP compounds and can be made into a portable detector for OP nerve agents. Here we demonstrate a systematic study to develop the EFNMR signature space of 31 nerve-agent-related OP compounds, including surrogates, simulants, synthetic precursors, decomposition products, pesticides, and threat agents identified by the National Institutes of Health. The EFNMR spectral signatures are a diagnostic fingerprint of the molecular structure, and this study establishes the structure-signature relationships of this relatively unexplored signature space. The results indicate that EFNMR is a powerful analytical capability to distinguish and identify the unique structure of OP compounds, including nerve agents. While aimed at detection of nerve agents, this study also lays the foundations of using EFNMR for detection of any OP compound in the laboratory or in the field.

Deferasirox is an FDA-approved iron chelator used in the treatment of iron toxicity. In this work, we report the use of several deferasirox derivatives as lanthanide chelators. Solid-state structural studies of three representative trivalent lanthanide cations, La(III), Eu(III), and Lu(III), revealed the formation of 2:2 complexes in the solid state. A 1:1 stoichiometry dominates in DMSO solution, with K-a values of 472 +/- 14, 477 +/- 11, and 496 +/- 15 M-1 being obtained in the case of these three cations, respectively. Under the conditions of competitive precipitation in the presence of triethylamine, high selectivity (up to 80%) for lutetium(III) was observed in competition with La(III), Ce(III), and Eu(III). Theoretical calculations provided support for the observed selective crystallization.