Cerium(IV) Imido Complexes: Structural, Computational, and Reactivity Studies

Abstract

A series of alkali metal capped cerium(IV) imido complexes, [M(solv)][Ce═N(3,5-(CF)CH)(TriNOx)] (M = Li, K, Rb, Cs; solv = TMEDA, THF, EtO, or DME), was isolated and fully characterized. An X-ray structural investigation of the cerium imido complexes demonstrated the impact of the alkali metal counterions on the geometry of the [Ce═N(3,5-(CF)CH)(TriNOx)] moiety. Substantial shortening of the Ce═N bond was observed with increasing size of the alkali metal cation. The first complex featuring an unsupported, terminal multiple bond between a Ce(IV) ion and a ligand fragment was also isolated by encapsulation of a Cs counterion with 2.2.2-cryptand. This complex shows the shortest recorded Ce═N bond length of 2.077(3) Å. Computational investigation of the cerium imido complexes using DFT methods showed a relatively larger contribution of the cerium 5d orbital than the 4f orbital to the Ce═N bonds. The [K(DME)][Ce═N(3,5-(CF)CH)(TriNOx)] complex cleaves the Si-O bond in (MeSi)O, yielding the [(MeSiO)Ce(TriNOx)] adduct. The reaction of the rubidium capped imido complex with benzophenone resulted in the formation of a rare Ce(IV)-oxo complex, that was stabilized by a supramolecular, tetrameric oligomerization of the Ce═O units with rubidium cations.

Rare‐Earth Metal Diimide Complexes via Alkylaluminate Templating, Including a Ceric Derivative

“…The CeÀ N(imido) bond lengths of 2.114(2) and 2.133 (2) (3) ), stabilized by the tris(hydroxylaminato) ligand framework. [7,23] The CeÀCl bond length of 2.6699 (7)m atches those found for other ceric chlorides coordinatedb yo xygenbased ligands (2.643-2.793 ) [17e, 24] or for (C 5 H 5 ) 3 CeCl (2.6666 (7) ). [25] Further non-redox reactivity studies of complexes 1-Ln were performedw ith the diamagnetic lanthanum derivative.…”

“…[2,3] In the meantime, several types of discrete mono-rareearth metal organoimide complexes have been reported (Figure 1, A-D). [4][5][6][7][8][9][10] The first terminal rare-earthm etal imide complex [LSc(NAr)(DMAP)] (A-type;L = MeC(NAr)CHC-(Me)((NCH 2 CH 2 N(Me)CH 2 CH 2 NMe 2 ), Ar = C 6 H 3 iPr 2 -2,6, DMAP = 4dimethylaminopyridine) was described by Chen et al exploiting aL ewis base-promoted methane elimination from as candium(III)m ethyl anilide complex, [4] and its reactivity investigated comprehensively. [1c] Other fully characterized A-type imides comprise additional Sc III derivatives [5] and our terminal lutetium and yttrium imide complexes [Tp tBu,Me Ln(NAr)(DMAP)] (Ln = Y, Ar = C 6 H 3 Me 2 -2,6;L n = Lu, Ar = C 6 H 3 (CF 3 ) 2 -3,5), [6] while Schelter's Ce IV imide[ Cs (2.2.2-cryptand)][(TriNOx)Ce{N(C 6 H 3 (CF 3 ) 2 -3,5)}] (TriNOx = [{(2-tBuNO)C 6 H 4 CH 2 } 3 N] 3À )f eatures an anionic rare-earth metal fragment (B-type).…”

“…[1c] Other fully characterized A-type imides comprise additional Sc III derivatives [5] and our terminal lutetium and yttrium imide complexes [Tp tBu,Me Ln(NAr)(DMAP)] (Ln = Y, Ar = C 6 H 3 Me 2 -2,6;L n = Lu, Ar = C 6 H 3 (CF 3 ) 2 -3,5), [6] while Schelter's Ce IV imide[ Cs (2.2.2-cryptand)][(TriNOx)Ce{N(C 6 H 3 (CF 3 ) 2 -3,5)}] (TriNOx = [{(2-tBuNO)C 6 H 4 CH 2 } 3 N] 3À )f eatures an anionic rare-earth metal fragment (B-type). [7] The mostly ionic Ln = N imido bondingc an also be stabilized by Lewis acid (LA) coordination( C/D-type). Mindiola et al reported that methane eliminationf rom as candium(III) methyl anilide complex cannot only be induced by aL ewis base but also by aL ewis acid such as AlMe 3 to yield isolable complex [(PNP)Sc{N(Ar)AlMe 3 }] (PNP = N[2P-(CHMe 2 ) 2 -4-methylphenyl] 2 ,Ar = C 6 H 3 iPr 2 -2,6).…”

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 ) .…”

Ceric Ammonium Nitrate and Ceric Ammonium Chloride as Precursors for Ceric Siloxides: Ammonia and Ammonium Inclusion

“…The Ce-O distances in five-coordinate 6(py) [2.101(1) -2.120(1) Å] are similar to those observed in seven-coordinate complex 3 or six-coordinate [Ce(OSiPh 3 ) 4 (DME)] [Ce-O Si 2.098(1) -2.133(1) Å], [5] but slightly shorter than found in the metallasilsesquioxane complex [Ce-{(c-C 6 H 11 ) 8 [25] Considering the different bonding in tetra-and trivalent cerium complexes, [55] an increasing contribution of π-backbonding between the non-bonding oxygen orbitals and to some degree stronger involved 5d and 4f-orbitals in Ce IV relative to Ce III complexes is expected. [32d, [55][56][57][58][59] Accordingly, 6(py) displays longer Si-O Ce bond lengths (ΔSi-O Ce : 0.030-0.034 Å) in comparison with 7, which is the result of weakened bonds due to an increase in π-backbonding within the Ce-O bond. As a consequence, also less bent Ce-O-Si bond angles are measured in the structure of the Ce IV complex.…”