Two-electron oxidation of a homoleptic U(iii) guanidinate complex by diphenyldiazomethane

Abstract

Reaction of the first homoleptic U(iii) guanidinate complex with diphenyldiazomethane results in two-electron oxidation of U(iii) to U(v) and isolation of a U(v) hydrazido complex. Corresponding U(v) imido, U(v) oxo, and U(iv) azido complexes were also synthesized for structural comparison.

Series of Tetravalent Actinide Amidinates: Structure Determination and Bonding Analysis

“…In each compound, the metal center is coordinated by three amidinate ligands and one chlorido or azido ligand, respectively. The resulting coordination geometry can be best described as a distorted monocapped octahedron, as already known for amidinates of [MClL 3 ] type with M = Ce(IV), 70 Th(IV), 71,72 U(IV), 2,73,74 and Np(IV) 36 (see Tables S6 and S7 in the SI). However, none of those reported actinide amidinates are bearing a chiral ligand, whereas in all compounds 1−8 the inherent ligand chirality induces a chirality-at-metal which leads to a crystallization solely as Δdiastereomers in the solid state.…”

“…Although the amidinate ligands are C 2 -symmetric, they bind asymmetrically to the metal center which is expressed by one longer bond length for the nitrogen atoms facing away from the (pseudo)­halide (i.e., N1, N3, N5, averaged to N a ) and a shorter bond length for all nitrogen atoms adjacent to the (pseudo)­halide (i.e., N2, N4, N6, averaged to N b ). A comparison with available literature data on tris­(amidinate) complexes of the [MClL 3 ] type (L = amidinate, M = Th, U, Ce) ,− shows that the difference between M–N a and M–N b is usually smaller than in 1 – 4 (see Tables S6 and S7 in the SI), indicating an increased steric repulsion between the bulky ( S )-PEBA ligands. As expected, this is also reflected in different angles ξ of the amidinate planes (expressed by the plane normals of N1–M1–N2, N3–M1–N4, and N5–M1–N6) against the metal–chloride/azide bond for all amidinates (see Table S3 in the SI).…”

“…The M–Cl distances in 1 , 2 , and 4 are similar to reported [MClL 3 ] (L = amidinate, M = Th, U, Ce) compounds (see Tables S6 and S7 in the SI). ,− …”

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

“…The N5−N6 distance of 1.178(6) Å is only marginally distinct from the N6−N7 distance of 1.124(7) Å, which is in agreement with the range of reported bond lengths (1.187(5)−1.162(6) Å in U(Tren TIPS )-(N 3 ) and 1.189(3)−1.153(3) Å in U(TIG) 3 (N 3 ) (TIG = N,N,N′,N″-tetraisopropylguanidinate)). 17,63 This phenomenon suggests a slight preference of the NN + −N 2− resonance form for azide over the − NN + =N − form, which might be induced by the coordination of the uranium ion, and also implies weak azide activation. The U1−N5 bond length of 2.293(4) Å is typical of that seen in U(Tren TIPS )(N 3 ) (2.305(3) Å) and U(TIG) 3 (N 3 ) (2.3260(18) Å).…”

Two-Electron Oxidative Atom Transfer at a Homoleptic, Tetravalent Uranium Complex

“…Two-electron oxidation chemistry of well-defined uranium complexes is dominated by the U 3+ /U 5+ couple and generally leads to the formation of metal-ligand multiple bonds (MLMBs). − The introduction of redox-active ligands into the coordination sphere of trivalent uranium complexes has led to the identification of two-electron chemistry that proceeds via a concomitant ligand redox event. − While the two-electron reduction of uranyl has been developed in recent years and the solid-state reduction of U 6+ to U 4+ has been demonstrated, − oxidative atom transfer reactions at tetravalent uranium complexes are comparatively rare and are only known in heteroleptic coordination complexes. − …”