Communication
Dalton Transactions
C39 angle (159.6(3)°) is also small compared to reported 10 I. S. Edworthy, A. J. Blake, C. Wilson and P. L. Arnold,
examples, supporting a U–Nketimido bond order of 1. The phenyl Organometallics, 2007, 26, 3684–3689.
rings of the ketimido ligand are splayed by 60.3(3)° and there is 11 C. Finn, S. Schnittger, L. J. Yellowlees and J. B. Love, Chem.
π–π stacking between one ring and the N-Dipp aromatic ring,
Commun., 2012, 48, 1392–1399.
12 P. L. Arnold, Chem. Commun., 2011, 47, 9005–9010.
with the distance between the ring centroids being 3.814(3) Å.40
−
Two UIV complexes with the NCPh2 ketimido ligand have 13 O. P. Lam, C. Anthon and K. Meyer, Dalton Trans., 2009,
36
been reported previously: Cp*2U(NCPh2)2 and Cp*2U(2,6-N-
9677.
Dipp-C6H3)(NCPh2).39 Both have almost linear U–Nketimido–C 14 O. Bénaud, J.-C. Berthet, P. Thuéry and M. Ephritikhine,
bond angles (173.4(6)°, 176.5(5)° in the former and 178.2(5)° Inorg. Chem., 2010, 49, 8117–8130.
in the latter) and shorter U–Nketimido bond lengths (2.179(6) Å 15 E. M. Matson, W. P. Forrest, P. E. Fanwick and S. C. Bart,
and 2.185(5) Å, and 2.199(4) Å in the latter) compared to U(LD)-
J. Am. Chem. Soc., 2011, 133, 4948–4954.
N′′2(NCPh2). Multiple bond character in the U–Nketimido bond 16 B. R. Van Ausdall, J. L. Glass, K. M. Wiggins, A. M. Aarif
is thus apparent for all three. and J. Louie, J. Org. Chem., 2009, 74, 7935–7942.
To conclude, the complexes M(LR)N′′2 all react rapidly to 17 A. M. Voutchkova, M. Feliz, E. Clot, O. Eisenstein and
incorporate an equivalent of CO2, and affording trimethylsilyl R. H. Crabtree, J. Am. Chem. Soc., 2007, 129, 12834–12846.
isocyanate from silylamido ligand conversion. The resultant 4f 18 M. Smiglak, J. D. Holbrey, S. T. Griffin, W. M. Reichert,
metal complexes cannot be isolated due to loss of the carbene
ligand and decomposition. The U complexes retain the
carbene ligand, but have poor solubility and are tentatively
R. P. Swatloski, A. R. Katritzky, H. Yang, D. Zhang,
K. Kirichenko and R. D. Rogers, Green Chem., 2007, 9,
90–98.
assigned as U(LR)(N′′)(OSiMe3)(OCNSiMe3). Equally insoluble 19 I. Tommasi and F. Sorrentino, Tetrahedron Lett., 2005, 46,
complexes are made from reactions with COS. A reversible labi-
lisation of the NHC group to bind and activate CO2 would 20 P. L. Arnold, Z. R. Turner, R. M. Bellabarba and
account for the observed reactions. NHC lability alone is most R. P. Tooze, Chem. Sci., 2011, 2, 77–79.
important to allow the reaction between CO and M(LR)N′′2 to 21 S. M. Mansell, N. Kaltsoyannis and P. L. Arnold, J. Am.
occur, since it allows an oxidative metallation to occur for Chem. Soc., 2011, 133, 9036–9051.
U. The result, in stark contrast with the reactivity of UN′′3, is 22 I. J. Casely, S. T. Liddle, A. J. Blake, C. Wilson and
the insertion of CO into the U–C bond of a cyclometallated P. L. Arnold, Chem. Commun., 2007, 5037–5039.
2141.
silylamido ligand of U(LR)N′′({CH2}SiMe2N{SiMe3}) to form 23 P. L. Arnold, Z. R. Turner, N. Kaltsoyannis, P. Pelekanaki,
the UIV complex U(LR)N′′(OC{CH2}SiMe2N{SiMe3}), and no evi-
R. M. Bellabarba and R. B. Tooze, Chem.–Eur. J., 2010, 16,
9623–9629.
dence of the reductive coupling of CO was observed. Finally,
the reaction of U(LD)N′′2 with diphenyldiazomethane affords 24 M.-J. Crawford, P. Mayer, H. Nöth and M. Suter, Inorg.
the UIV complex U(LD)N′′2(NCvPh2), a rare uranium ketimide
complex. Investigations are underway to identify suitable ancil- 25 L. R. Sita, J. R. Babcock and R. Xi, J. Am. Chem. Soc., 1996,
Chem., 2004, 43, 6860–6862.
lary ligands to allow the stabilisation of NHC-labilised inter-
mediates containing the carbon oxides.
118, 10912–10913.
26 H. Phull, D. Alberti, I. Korobkov, S. Gambarotta and
P. H. M. Budzelaar, Angew. Chem., Int. Ed., 2006, 45,
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27 A. P. Markus, N. Bernhard and D. Kurt, Z. Anorg. Allg.
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1336 | Dalton Trans., 2013, 42, 1333–1337
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