Rational Design of a Tripodal Ligand for U(IV): Synthesis and Characterization of a U–Cl Species and Insights into Its Reactivity

Abstract

The rational design and synthesis of the Trapen ligand (1, tris­(2-aminobenzyl)­amine) with a tripodal scaffold is reported. Treatment of Trapen with n-BuLi and TMSCl results in the formation of the corresponding complex [(TrapenTMS)­(Li)3] (2). In particular, 2 reacts with UCl4 to give the important synthon uranium­(IV) complex [U­(TrapenTMS)­(Cl)] (3) with all of the nitrogen atoms bound to the uranium­(IV) center. Moreover, the pseudohalogen congener [U­(TrapenTMS)­(OCP)] (4) or the azide analogue [U­(TrapenTMS)­(N3)] (5) could be obtained when [U­(TrapenTMS)­(Cl)] (3) was treated with NaOCP­(dioxane)2.5 or NaN3 by a salt metathesis approach. In addition, the reaction of KC8 with [U­(TrapenTMS)­(Cl)] (3) did not afford the desired U­(III) complex but produced the unexpected bridging diuranium oxo complex [U­(TrapenTMS)2(μ-O)] (6). All of the compounds were isolated in the solid state and characterized by NMR, X-ray crystal diffraction, and FT-IR, and UV–vis–NIR as well as elemental analyses and SQUID magnetization measurements. The combined experimental analyses and chemical calculations support all of the formal uranium­(IV) species.

Synthesis of Trapen Ligand-Based U(IV) and Th(IV) 2-Phosphaethynolate Complexes and Comparison of Covalency with Corresponding Ti(IV) Analogues

“…In contrast, the thorium complex [Th­(Tren TIPS )­(OCP)] exhibits a single resonance at −339.9 ppm. The crystal structure of 3B reveals Th–O, O–C, and C–P distances of 2.316(5), 1.242(9), and 1.569(8) Å, respectively, and these data compare well with other Th–OCP complexes. , In the IR spectrum, a strong absorption at 1678 cm –1 was attributed to the (OCP) − asymmetric stretch, indicating an O-bound complex. − The synthesis and structural identification of 3C followed the reported work by our group …”

“…35−38 The synthesis and structural identification of 3C followed the reported work by our group. 39 Electronic Structures of Complexes 3A, 3B, and 3C. The selected M−O (M = Ti, Th, or U), O−C, and C−P bond distances at the PBE0/RECP-SEG/6-31G(d) level of theory are presented in Table 1.…”

Recent advances in the chemistry of the phosphaethynolate and arsaethynolate anions

“…In 2020, Mei and Shi et al synthesized the reactive synthon U(Trapen TMS )Cl ( 107 ) using a novel trapen ligand (tris(2-aminobenzyl)amine) and examined its reactivity towards anionic nucleophiles. 98 The reaction of [(Trapen TMS )(Li) 3 ] with UCl 4 at −78 °C in THF solution led to the formation of U(Trapen TMS )Cl ( 107 ). SCXRD analysis confirmed a distorted-trigonal bipyramidal geometry around the uranium center with the U–N amido bond distance in the range 2.244(6)–2.225(6) Å and U–N amine bond length of 2.631(6) Å, which are in accordance with earlier reported data.…”

A Theoretical Study of Unsupported Uranium–Ruthenium Bonds Based on Tripodal Ligands

“…Subsequently, they obtained a series of unsupported An–M bonds based on tripodal ligands. − Zhu and co-workers constructed a series of heterometallic clusters with multiple U–Ni and U–Rh bonds based on the Tren ligand [Tren P– i Pr 2 ] 3– [Tren P– i Pr 2 = N­(CH 2 CH 2 NP i Pr 2 ) 3 ]. , Meyer and co-workers developed another type of tripodal ligand, [( Ad,Me ArO) 3 N] 3– [( Ad,Me ArO) 3 N is the trianion of tris­(2-hydroxy-3-adamantyl-5-methylbenzyl)­amine] with aryloxy groups, − in which there are three coordinated O atoms. We recently reported a new tripodal ligand, Trapen, that is more rigid than Tren, which can be conveniently converted into the corresponding Trapen–U precursor. The tripodal ligands shown in Scheme are good donors for the construction of uranium precursors, such as [Tren TMS U–Cl], [Tren P– i Pr 2 U–Cl], and [Trapen TMS U–Cl], with amine groups, by which one can further obtain U–M bonds.…”

“…Meyer and co-workers developed another type of tripodal ligand, [( Ad, Me ArO) 3 N] 3 − [( Ad,Me ArO) 3 N is the trianion of tris(2-hydroxy-3-adamantyl-5-methylbenzyl)amine] with aryloxy groups,24−27 in which there are three coordinated O atoms. We recently reported a new tripodal ligand, Trapen,28 that is more rigid than Tren, which can be conveniently converted into the corresponding Trapen−U precursor. The tripodal ligands shown in Scheme 1 are good donors for the construction of uranium precursors, such as [Tren TMS U−Cl], [Tren P−iPr 2 U−Cl], and [Trapen TMS U−Cl], with amine groups, by which one can further obtain U− M bonds.…”