title: Uranium-Carbene-Imido Metalla-Allenes: Ancillary-Ligand-Controlled cis-/trans-Isomerisation and Assessment of trans Influence in the R2 C=U(IV) =NR' Unit (R=Ph2 PNSiMe3 ; R'=CPh3 ).
abstract: Uranium(IV)-carbene-imido complexes [U(BIPM(TMS) )(NCPh3 )(κ(2) -N,N'-BIPY)] (2; BIPM(TMS) =C(PPh2 NSiMe3 )2 ; BIPY=2,2-bipyridine) and [U(BIPM(TMS) )(NCPh3 )(DMAP)2 ] (3; DMAP=4-dimethylamino-pyridine) that contain unprecedented, discrete R2 C=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) .
authors.affiliation: School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
authors.forename: Erli
authors.initials: E
authors.lastname: Lu
authors.affiliation: School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
authors.forename: Oliver J
authors.initials: OJ
authors.lastname: Cooper
authors.affiliation: School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
authors.forename: Floriana
authors.initials: F
authors.lastname: Tuna
authors.affiliation: School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
authors.forename: Ashley J
authors.initials: AJ
authors.lastname: Wooles
authors.affiliation: School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK. nikolas.kaltsoyannis@manchester.ac.uk.
authors.forename: Nikolas
authors.initials: N
authors.lastname: Kaltsoyannis
authors.affiliation: School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK. steve.liddle@manchester.ac.uk.
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Liddle
keywords: carbenes; density functional calculations; imido compounds; metalla-allenes; uranium