Benzoquinonoid-bridged dinuclear actinide complexes

Abstract

We report the coordination chemistry of the tripodal tris[2-amido(2-pyridyl)ethyl]amine ligand, L, with thorium(iv) and uranium(iv). Using a salt-metathesis strategy from the potassium salt of this ligand, K3L, new actinide complexes were isolated, namely the dimeric thorium complex [ThCl(L)] (1) and the monomeric uranium complex UI(THF)(L) (2); under different crystallisation conditions, the dimeric uranium complex is also isolated, [UI(L)] (2-dimer). With the aim of studying electronic phenomena such as magnetic exchange between two actinide ions, we have synthesised the first examples of dinuclear, quinoid-bridged actinide complexes from dianionic 2,5-bis[2,6-(diisopropyl)anilide]-1,4-benzoquinone (QDipp) and 2,5-bis[2-(methoxy)anilide]-1,4-benzoquinone (QOMe) ligands. The resulting complexes are [Th(L)]Q (3), [Th(THF)(L)]Q (5) and [U(L)]Q (6). The targeted [U(L)]Q complex (4) could not be isolated. All isolated complexes have been characterised by spectroscopic methods and X-ray crystallography. The uranium(iv) complexes 2-dimer and 6 have been studied by SQUID magnetometry but indicate that there is negligible magnetic exchange between the two uranium(iv) ions. The reduced form of 6, [K(18-c-6)][6-] is unstable and highly sensitive, but X-ray crystallography indicates that it is a novel UU complex bridged by a quinoid-radical.

DFT Investigations of the Magnetic Properties of Actinide Complexes

“…They are rather similar to those of the U V (µ-O)2U V complex (Figure 20). More recently (2017), the first benzoquinonoid-bridged dinuclear actinide complexes were reported by S. Hohloch et al [156] The target dinuclear systems with different structures, i.e., UI(L)]2, [Th(L)]2Q Dipp , [Th(THF)(L)]2Q OMe and [U(L)]2Q OMe associated with the tripodal tris[2-amido(2pyridyl)ethyl]amine ligand L, have been synthesized from the dianionic 2,5-bis [2,6-(diisopropyl)anilide]-1,4-benzoquinone (Q Dipp ) and 2,5-bis[2-(methoxy)anilide]-1,4-benzoquinone (Q OMe ) ligands, as depicted for the quinoid-bridged U IV /U IV diuranium system in Figure 23. As reported by the authors, magnetic measurements of the duranium(IV) iodide [UI(L)]2 and quinoid [U(L)]2Q OMe bridged species, which exhibit long intermetallic U IV …U IV distances i.e., 5.125(1) Å and 8.904(1) Å respectively, indicate that there is weak magnetic exchange between the two uranium(IV) ions which was not quantified from the DC susceptibility measurements.…”

“…More recently (2017), the first benzoquinonoid-bridged dinuclear actinide complexes were reported by S. Hohloch et al [156] The target dinuclear systems with different structures, i.e., UI As reported by the authors, magnetic measurements of the duranium(IV) iodide [UI(L)]2 and quinoid [U(L)]2Q OMe bridged species, which exhibit long intermetallic U IV …U IV distances i.e., 5.125(1) Å and 8.904(1) Å respectively, indicate that there is weak magnetic exchange between the two uranium(IV) ions which was not quantified from the DC susceptibility measurements. Furthermore, as reported in the study, the low-temperature susceptibility data indicate that the ground states for the two U IV /U IV dimer should be non-magnetic singlets.…”

“…SOMO-2 of the [U(L)] 2 Q OMe quintet state system. Plot surfaces displayed with an iso-value of 0.02 au (reprinted with permission from[156], the Royal Society of Chemistry, 2017).…”

Theoretical Investigation of the Electronic Structure and Magnetic Properties of Oxo-Bridged Uranyl(V) Dinuclear and Trinuclear Complexes

“…[17][18][19][20][21] Consequently, since the discovery of the slow magnetic relaxation in the mononuclear complex U(Ph2BPz2)3, 22 an increasing number of studies have been directed to develop SMMs based on actinide-containing systems. [23][24][25][26][27][28] These studies include mono [29][30][31][32][33][34][35][36][37][38] and polynuclear systems [39][40][41] and heteropolymetallic uranium-3d metal complexes. [42][43][44][45][46][47][48] Notably, uranium not only shows large spin-orbit coupling but in addition the more diffuse nature of 5f orbitals compared to 4f orbitals, 36,40 is expected to allow higher p-f orbital overlap and hence stronger magnetic couplings.…”

Direct nucleophilic trifluoromethylation of carbonyl compounds by potent greenhouse gas, fluoroform: Improving the reactivity of anionoid trifluoromethyl species in glymes

“…5f ) also showed the coordination of the CF 3 to the K center via two of the three fluorine atoms. Also, using the X-ray data for [K(18-crown-6)(THF)] + 54 , the structure of [K(18-crown-6)(THF)(CF 3 )] was computed (Fig. 5g ) 48 , 49 , 53 .…”