Rare‐Earth‐Metal Methyl, Amide, and Imide Complexes Supported by a Superbulky Scorpionate Ligand

Abstract

The reaction of monomeric [(Tp(tBu,Me) )LuMe2 ] (Tp(tBu,Me) =tris(3-Me-5-tBu-pyrazolyl)borate) with primary aliphatic amines H2 NR (R=tBu, Ad=adamantyl) led to lutetium methyl primary amide complexes [(Tp(tBu,Me) )LuMe(NHR)], the solid-state structures of which were determined by XRD analyses. The mixed methyl/tetramethylaluminate compounds [(Tp(tBu,Me) )LnMe({μ2 -Me}AlMe3 )] (Ln=Y, Ho) reacted selectively and in high yield with H2 NR, according to methane elimination, to afford heterobimetallic complexes: [(Tp(tBu,Me) )Ln({μ2 -Me}AlMe2 )(μ2 -NR)] (Ln=Y, Ho). X-ray structure analyses revealed that the monomeric alkylaluminum-supported imide complexes were isostructural, featuring bridging methyl and imido ligands. Deeper insight into the fluxional behavior in solution was gained by (1) H and (13) C NMR spectroscopic studies at variable temperatures and (1) H-(89) Y HSQC NMR spectroscopy. Treatment of [(Tp(tBu,Me) )LnMe(AlMe4 )] with H2 NtBu gave dimethyl compounds [(Tp(tBu,Me) )LnMe2 ] as minor side products for the mid-sized metals yttrium and holmium and in high yield for the smaller lutetium. Preparative-scale amounts of complexes [(Tp(tBu,Me) )LnMe2 ] (Ln=Y, Ho, Lu) were made accessible through aluminate cleavage of [(Tp(tBu,Me) )LnMe(AlMe4 )] with N,N,N',N'-tetramethylethylenediamine (tmeda). The solid-state structures of [(Tp(tBu,Me) )HoMe(AlMe4 )] and [(Tp(tBu,Me) )HoMe2 ] were analyzed by XRD.

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

“…Although the structural parameters of the Ln/M heterobimetalic complexes Ln[M(CH3)4]3 (M = Al, Ga) [21][22][23] and the derived half-sandwich [24], metallocene [25], and scorpionate complexes [10,26,27] are similar, the reactivity, in some cases, is dramatically different [10,26,27]. For example, previous studies from our laboratory revealed that [(Tp )Ln(CH3){Al(CH3)4}], which yields complexes of type III [9,10].…”

“…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].…”

Piano-Stool Lutetium Amido and Imido Compounds Supported by a Constrained Bis(oxazoline)cyclopentadienyl Ligand

“…1 H, 13 C{ 1 H}, and 11 B NMR spectra were collected on Bruker AVII 700 or 600 spectrometers, a Bruker DRX-400 spectrometer, or a MR-400 spectrometer. 15 73 mmol) was placed in a 100 mL Schlenk flask and dissolved in THF (30 mL).…”

“…12 In the presence of alkylaluminum compounds, heterobimetallic compounds of the type [Ln]{(μ-R)(μ-NR′)AlR 2 } are obtained. 13 Bridging imido groups are also common in scandium chemistry. For example, insertion of benzonitrile into a Sc−C bond gives the μ 2 -imido complex [{C 5 H 4 (CH 2 ) 2 NMe 2 }Sc{μ 2 -NC(Ph)C 6 H 10 }] 2 , which is proposed to form through a mononuclear scandium imido intermediate.…”

“…16a In addition, the Lu−N distances in the AlMe 3 -coordinated Tp tBu,Me Lu{(μ-Me)(μ-NR)AlMe 2 } (R = tBu, 2.081(3) Å, R = Ad, 2.083(2) Å) are significantly shorter than those in 4. 13 The shorter distances in tris(pyrazolyl)borate-supported compounds may be a result of their lower coordination number vs 4, a reduced steric demand of the bridging AlMe 3 moiety in the [Lu]{(μ-Me)(μ-NR)AlMe 2 } structure vs two ligands in the [Lu]{NHB-(C 6 F 5 ) 2 }C 6 F 5 structure, or from an electronic effect.…”