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The reaction between [UO2F2] and an excess of Me3SiN3 in acetonitrile solution results in fluoride-azide exchange and the uranium(VI) dioxodiazide adduct [UO2(N3)2⋅CH3CN] was isolated in quantitative yield. The subsequent reaction of [UO2(N3)2⋅CH3CN] with 2,2′-bipyridine (bipy) resulted in the formation of the azido-bridged binuclear complex [(bipy)2(UO2)2(N3)4]. The triazido anion [(bipy)UO2(N3)3]− was obtained by the reaction of [UO2(N3)2⋅CH3CN] with stoichiometric amounts of bipy and the ionic azide [PPh4][N3]. The reaction of [UO2(N3)2] with two equivalents of the [PPh4][N3] resulted in the formation of the mononuclear tetraazido anion [UO2(N3)4]2− as well as the azido-bridged binuclear anion [(UO2)2(N3)8]4−. The novel uranium oxoazides were characterized by their vibrational spectra and in the case of [(bipy)2(UO2)2(N3)4]⋅CH3CN, [PPh4][(bipy)UO2(N3)3], [PPh4]2[UO2(N3)4], [PPh4]2[UO2(N3)4]⋅2CH3CN, and [PPh4]4[(UO2)2(N3)8]⋅4CH3CN by their X-ray crystal structures. [ABSTRACT FROM AUTHOR]

The reaction between [UO2F2] and an excess of Me3SiN3 in acetonitrile solution results in fluoride-azide exchange and the uranium(VI) dioxodiazide adduct [UO2(N3)2⋅CH3CN] was isolated in quantitative yield. The subsequent reaction of [UO2(N3)2⋅CH3CN] with 2,2′-bipyridine (bipy) resulted in the formation of the azido-bridged binuclear complex [(bipy)2(UO2)2(N3)4]. The triazido anion [(bipy)UO2(N3)3]− was obtained by the reaction of [UO2(N3)2⋅CH3CN] with stoichiometric amounts of bipy and the ionic azide [PPh4][N3]. The reaction of [UO2(N3)2] with two equivalents of the [PPh4][N3] resulted in the formation of the mononuclear tetraazido anion [UO2(N3)4]2− as well as the azido-bridged binuclear anion [(UO2)2(N3)8]4−. The novel uranium oxoazides were characterized by their vibrational spectra and in the case of [(bipy)2(UO2)2(N3)4]⋅CH3CN, [PPh4][(bipy)UO2(N3)3], [PPh4]2[UO2(N3)4], [PPh4]2[UO2(N3)4]⋅2CH3CN, and [PPh4]4[(UO2)2(N3)8]⋅4CH3CN by their X-ray crystal structures. [ABSTRACT FROM AUTHOR]

Uranium(IV)-carbene-imido complexes [U(BIPMTMS)(NCPh3)(κ2- N, N′-BIPY)] ( 2; BIPMTMS=C(PPh2NSiMe3)2; BIPY=2,2-bipyridine) and [U(BIPMTMS)(NCPh3)(DMAP)2] ( 3; DMAP=4-dimethylamino-pyridine) that contain unprecedented, discrete R2C=U=NR′ units are reported. These complexes complete the family of E=U=E (E=CR2, NR, O) metalla-allenes with feasible first-row hetero-element combinations. Intriguingly, 2 and 3 contain cis- and trans-C=U=N units, respectively, representing rare examples of controllable cis/ trans isomerisation in f-block chemistry. This work reveals a clear-cut example of the trans influence in a mid-valent uranium system, and thus a strong preference for the cis isomer, which is computed in a co-ligand-free truncated model-to isolate the electronic trans influence from steric contributions-to be more stable than the trans isomer by approximately 12 kJ mol−1 with an isomerisation barrier of approximately 14 kJ mol−1. [ABSTRACT FROM AUTHOR]

Uranium(IV)-carbene-imido complexes [U(BIPMTMS)(NCPh3)(κ2- N, N′-BIPY)] ( 2; BIPMTMS=C(PPh2NSiMe3)2; BIPY=2,2-bipyridine) and [U(BIPMTMS)(NCPh3)(DMAP)2] ( 3; DMAP=4-dimethylamino-pyridine) that contain unprecedented, discrete R2C=U=NR′ units are reported. These complexes complete the family of E=U=E (E=CR2, NR, O) metalla-allenes with feasible first-row hetero-element combinations. Intriguingly, 2 and 3 contain cis- and trans-C=U=N units, respectively, representing rare examples of controllable cis/ trans isomerisation in f-block chemistry. This work reveals a clear-cut example of the trans influence in a mid-valent uranium system, and thus a strong preference for the cis isomer, which is computed in a co-ligand-free truncated model-to isolate the electronic trans influence from steric contributions-to be more stable than the trans isomer by approximately 12 kJ mol−1 with an isomerisation barrier of approximately 14 kJ mol−1. [ABSTRACT FROM AUTHOR]