Organoaluminum-Assisted Formation of Rare-Earth Metal Imide Complexes

Abstract

The μ2-imide complexes [Ln(AlMe4)(μ2-Nmes*)] x (mes* = C6H2 tBu3-2,4,6) (Ln = Y, La, Nd, Lu) are synthesized from homoleptic heterobimetallic complexes Ln(AlMe4)3 utilizing two distinct protocols: reaction with 2,4,6-tri-tert-butylaniline in hexane via methane elimination or with potassium (2,4,6-tri-tert-butylphenyl)amide in toluene according to a salt metathesis–protonolysis tandem reaction. Complexes [Ln(AlMe4)(μ2-Nmes*)]2 (Ln = Y, Nd, Lu) revealed isomorphous solid-state structures, featuring an asymmetrically bridged Ln2N2 core with very short Ln–N distances (2.071(1)–2.155(3) Å). In the solid-state structure of the lanthanum derivative similar dimeric subunits assemble as La4Al4 oligomers through μ2-η1:η2-bridging tetramethylaluminato moieties. [La(AlMe4)(μ2-Nmes*)]4 displays La---arene interactions (2.702(6) Å) that are considerably shorter than the La(μ-CH3)aluminato bond lengths.

Holmium(III) Supermesityl-Imide Complexes Bearing Methylaluminato/Gallato Ligands

“…While a series of dimeric LA-stabilized rare-earth metal imides (type II) has been reported previously [7], we now report on additional aniline-derived rare-earth metal imide complexes employing methylaluminate and methylgallate complexes. The intention was to investigate fundamental differences of organogallium versus organoaluminum moieties since GaMe3 should behave as a weaker LA towards nitrogen than AlMe3.…”

“…The µ2-imide complexes [Ln{Al(CH3)4}(µ2-Nmes*)]x (Ln = Y, La, Nd, Lu; mes* = C6H2tBu3-2,4,6) were previously obtained from homoleptic heterobimetallic complexes Ln[Al(CH3)4]3 utilizing two distinct protocols: reaction with 2,4,6-tri-tert-butylaniline in n-hexane via methane elimination or with potassium (2,4,6-tri-tert-butylphenyl)amide in toluene according to a salt metathesis-protonolysis tandem reaction [7]. Similarly, the reaction of Ho[M(CH3)4]3 (M = Al, Ga) with H2Nmes* or K[NH(mes*)], respectively, led to dimeric complexes [Ho{M(CH3)4}(µ2-Nmes*)]2 (M = Al (1), Ga (2)) (Scheme 1).…”

“…A preliminary reactivity study of yttrium congener [Y{Al(CH3)4}(µ2-Nmes*)]2 [7] was performed in order to assess the feasibility of exchanging the AlMe4 …”

“…Then 2,4,6-tri-tert-butylaniline was obtained from Aldrich and used as received. Potassium (2,4,6-tri-tert-butylphenyl)amide was synthesized according to literature procedures [7]. Homoleptic complexes [Ho{Al(CH3)4}3] [22,29] and [Ho{Ga(CH3)4}3] [30,31] (2) were prepared according to literature methods.…”

“…Another synthesis strategy was developed by Evans et al, [4]. We and others succeeded in the isolation of a series of rare-earth metal complexes ( Figure 1, II-III, secondary interactions are not shown), by adopting the strategy of organoaluminum-assisted imide formation [5][6][7][8][9][10]. Similarly, deprotonation of lanthanide anilide complexes was achieved via treatment with butyllithium, affording complexes of type IV [11].…”