Synthesis of Differently Substituted tacn‐Based Ligands: Towards the Control of Solubility and Electronic and Steric Properties of Uranium Coordination Complexes

Abstract

Starting from phenols R1,R2ArOH (5) and the anisole derivative 3,5‐di‐tert‐butyl‐2‐methoxybenzyl bromide (13), a series of new tacn‐based ligands (R1,R2ArOR3)3tacn (2) have been synthesized with substituents of varying bulkiness and electronic nature at the ortho and para positions with respect to the oxygen coordination site. It was observed that these groups not only determine the steric shielding and solubility properties of 2, but also deactivate the reactivity of the phenols in the modified Mannich reaction when electron‐withdrawing groups are introduced at the para position in 5. Treatment of the ligands with UCl4 in thf led to the isolation of four uranium(IV) chloro complexes [{(R1,R2ArO)3tacn}UIVCl] (14), which were characterized by different spectroscopic and physical methods (e.g., 1H NMR, UV/Vis, SQUID), corroborating the +4 oxidation state in 14. Single‐crystal X‐ray structure analyses revealed that 14a·CH2Cl2·CH3CN and 14b·1.25CH2Cl2 crystallize in the chiral, orthorhombic space group P212121 [a = 24.934(3), b = 27.941(3), c = 9.045(1) Å, V = 6302(2) Å3, Z = 4] and the chiral, hexagonal space group P63 [a = 22.097(3), c = 17.941(2) Å, V = 7587(2) Å3, Z = 4], respectively. Interestingly, complexes 14a,b self‐organize in the solid state into homochiral 1D polymeric superstructures as a result of weak intermolecular C–H···Cl contacts.

Uranium(iv) terminal hydrosulfido and sulfido complexes: insights into the nature of the uranium–sulfur bond

“…After crystallization, a conglomerate of enantiomerically pure crystals was found for 4 with an A-configuration of the uranium center in the analyzed crystal. 47 , 51 Complexes 2–4 are stable in the solid form or in THF solution for at least 3 weeks without any notable decomposition.…”

“… 50 , 61 , 62 Tetravalent uranium ions possess an f 2 valence electron configuration, which results in a non-magnetic ground state at very low temperatures; and consequently, strongly temperature-dependent magnetic moments, μ eff , with values typically ranging from 0.3 μ B at 2 K to 2.8 μ B at room temperature. 36 , 46 , 50 , 51 , 53 , 61 , 63 , 64 …”

Boroquinol Complexes with Fused Extended Aromatic Backbones: Synthesis and Optical Properties

“…This clearly demonstrates that the reaction pathway to the desired product 4a is driven by the oxidant, and the one to the dearylation product by the amount of acid. To prove the tautomerization and CÀC cleavage steps, salicylaldehyde ether 3 has been synthesized [25] (see the Supporting Information) andu sed in the reaction with biaryl 1a under the same conditions as those of the free phenol (10 %T FA,a ir;T able 1, entry 10). As expected, no formation of dearylated product could be observed because aP ictet-Spengler intermediate with ap henol ether cannotu ndergo tautomerization and only the corresponding phenanthridine 5a was detected in 66 %y ield.…”

Unbridged bidentate aluminum complexes supported by diaroylhydrazone ligands: Synthesis, structure and catalysis in polymerization of ε‐caprolactone and lactides

“…The solvents were distilled over sodium benzophenone ketyl under argon prior to use. 3,5‐di‐ tert ‐butyl‐2‐methoxybenzaldehyde was prepared following the reported procedures . All other chemicals were obtained from commercial vendors and used as received.…”