Uranium-Carbene-Imido Metalla-Allenes: Ancillary-Ligand-Controlled cis-/trans-Isomerisation and Assessment of trans Influence in the R2C=UIV=NR′ Unit (R=Ph2PNSiMe3; R′=CPh3)
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- 作者：Dr. Erli Lu ; Dr. Oliver J. Cooper ; Dr. Floriana Tuna ; Dr. Ashley J. Wooles ; Prof. Nikolas Kaltsoyannis and Prof. Stephen T. Liddle
- 刊名：Chemistry - A European Journal
- 出版年：2016
- 出版时间：August 8, 2016
- 年：2016
- 卷：22
- 期：33
- 页码：11559-11563
- 全文大小：1449K
- ISSN：1521-3765
文摘
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.