An Alkali Metal-Capped Cerium(IV) Imido Complex

Abstract

Structurally authenticated, terminal lanthanide-ligand multiple bonds are rare and expected to be highly reactive. Even capped with an alkali metal cation, poor orbital energy matching and overlap of metal and ligand valence orbitals should result in strong charge polarization within such bonds. We expand on a new strategy for isolating terminal lanthanide-ligand multiple bonds using cerium(IV) complexes. In the current case, our tailored tris(hydroxylaminato) ligand framework, TriNOx(3-), provides steric protection against ligand scrambling and metal complex oligomerization and electronic protection against reduction. This strategy culminates in isolation of the first formal Ce═N bonded moiety in the complex [K(DME)2][Ce═N(3,5-(CF3)2C6H3)(TriNOx)], whose Ce═N bond is the shortest known at 2.119(3) Å.

Formation of a Ce(IV) Oxo Complex via Inner Sphere Nitrate Reduction

“…As with the  NLMO compositions, the other QTAIM metrics for the analogous U and Ce systems are very similar to one another, and indicate a significantly covalent M-O interaction, with  and H values amongst the largest (in an absolute sense) seen for f element bonds. Indeed, the present  and H are approximately double the value of the equivalent metrics of the M(IV)-C multiple bonds recently reported by Liddle et al 17 Pleasingly, the covalency trend Ce ≈ U > Th is the same in both our system and the BIPM TMS compounds.…”

A Combined Experimental and Theoretical Study of the Versatile Reactivity of an Oxocerium(IV) Complex: Concerted Versus Reductive Addition

“…Recently, we reported the isolation of the first Ce IV terminal oxo complex [(L OEt ) 2 Ce(=O)(H 2 O)] ⋅ MeC(O)NH 2 ( 1 ; L OEt − =[Co(η 5 ‐C 5 H 5 ){P(O)(OEt) 2 } 3 ] − ) (Scheme ) . This major breakthrough in cerium chemistry has been rapidly developed by excellent contributions from others, for example, in the synthesis of the first cerium(IV)–imido complexes . The initial reactivity studies of the oxocerium complex 1 are intriguing in their variation: we have found both a classical 1,2‐insertion without change of the Ce oxidation state ([2π+2π]‐type metathesis) and reductive insertion (Scheme ) .…”

Synthesis and Reduction of Uranium(V) Imido Complexes with Redox‐Active Substituents

“…In these compounds, the steric properties of the amide and imido ligands determinedt he overall geometry of the compounds. In compounds 2 and 3,t he imido ligand was the mosts terically demanding, which causedt he N = U-N amide bond angle to be largea tt he expense of decreasing the (5), U(1)ÀN(4) 1.960 (5), N(4)ÀC(19) 1.486 (7),C (19)-N(4)-U(1) 179.3 (4), N(4)-U(1)-N(1) 113.13 (19), N(1)-U(1)-N(2) 105.33(17);3-U(1)ÀN(1) 2.269(6), U(1)ÀN(2) 1.956 (9), N(2)ÀC(7) 1.502 (14), C(7)-N(2)-U(1) 180.000 (2), N(2)-U(1)-N(1) 115.23 (15), N(1)-U(1)-N(1) 103.15(18);4-U(1)ÀN(1) 1.9503 (14), U(1)ÀN(2) 2.2313 (14), U(1)ÀN(3) 2.2529 (14), U(1)ÀN(4) 2.2469 (14), N(1)ÀC(1) 1.387(2), C(1)-N(1)-U(1)172.32 (13), N(1)-U(1)-N(2) 99.51, N(2)-U(1)-N(3) 115.42 (5). N amide -U-N amide bond angles and lengthening the UÀN amide bonds.…”

“…This increase in bond polarization often results in relatively more reactive multiply‐bonded compounds. Recent efforts in this area have resulted in the first example of cerium–nitrogen and cerium–oxygen multiple bonds . However, relativistic effects dictate that uranium has more chemically active 6d and 5f orbitals, which leads to increased orbital overlap and covalency in U−E multiple bonds.…”

“…Recent efforts in this area have resulted in the first example of cerium-nitrogen and cerium-oxygen multiple bonds. [2,3] However,r elativistic effects dictate that uranium has more chemically active6 da nd 5f orbitals, which leads to increased orbitalo verlap andc ovalency in UÀEm ultiple bonds. Uranium-oxo complexes have been studied extensively,p articularly in the context of environmental transport and waste remediation efforts.…”