Methylaluminum‐Supported Rare‐Earth‐Metal Dihydrides

Abstract

Compounds combining the large rare-earth-metal (Ln) centers with the smallest anionic ligand, H À (hydrido), continue to pose challenging questions both in fundamental and applied chemistry. [1] The inherent bonding properties in solid-state binary LnH x phases (e.g., causing metallic behavior) as well as in ligand-supported molecular counterparts (revealing unique cluster chemistry, see Supporting Information) have been the focus of extensive research. Moreover, heterobimetallic solid-state materials, such as Ni 5 LaH x , feature approved rechargeable battery components or, such as LnAlH 6 (obtained from LnCl 3 and NaAlH 4 by the release of hydrogen), are discussed as intermediate-temperature hydrogen-storage materials. [2] On the other hand, the quest for soluble molecular hydrides has triggered immense research efforts. In the meantime, mono and dihydrido derivatives "L 2 LnH" and "LLnH 2 " (L = monoanionic ligand), respectively, are assigned a crucial role in a variety of stoichiometric and catalytic transformations, [3] whereas complexes of type [LnH 3 (Do) x ] (Do = neutral donor ligand) are still elusive. While mono hydride complexes can exist as monomers, e.g., [(C 5 H 2 tBu 3 ) 2 CeH], [4] dihydrido species "LLnH 2 ", carrying only one ancillary ligand per lanthanide center, tend to form polynuclear complexes (see Supporting Information) containing as few as two [5] and up to six lanthanide metal centers. [6] Several types of ancillary ligands have been employed in an effort to stabilize complexes of low nuclearity, including sterically demanding cyclopentadienyl derivatives such as C 5 Me 4 SiMe 3[6] tris(pyrazolyl)borato scorpionates, [7] tetraazacycloamido, [8] bis(phosphinophenyl)amido pincer, [5] and pyridylamido [9] ligands as well as chelating diamido ligands (see Supporting Information). [10] However, the synthesis of a monomeric rare-earth-metal dihydride was not successful to date.The group of Takats used the sterically demanding hydrotris(3-tert-butyl-5-methylpyrazolyl)borato ligand (Tp tBu,Me ) to stabilize Ln 2+ centers in species such as alkyls, [11] carbenes, [12] amides, [11b] halides, [11,13] or hydrides [14] and was also able to obtain lanthanide dihydride complexes using the less-bulky dimethyl, diisopropyl, or unsubstituted derivative of the Tp ligand, but reported the formation of a mixture of products for the more bulky Tp tBu,Me ligand

Rare‐Earth Metal Complexes with Terminal Imido Ligands

“…X‐ray diffraction studies revealed the expected molecular structure (see Figure S1). The Y–N(imide) bond lengths in 2 average 2.126 Å (three independent molecules in the unit cell) and lie well within the expected range compared to previously reported LA‐supported yttrium imide complexes 12b,12c,18. As for the previously synthesized B ′‐type imide complexes,12b,12c compound 2 could not be converted into a terminal imide complex, neither thermally nor by addition of neutral Lewis bases like 1,4‐dioxane, pyridine, tmeda ( N , N , N′ , N′ ‐tetramethylethylenediamine), or DMAP.…”

“…We applied the superbulky monoanionic Tp t Bu,Me {hydrotris(3‐ tert ‐butyl‐5‐methylpyrazolyl)borate} ligand to enter [Ln=X](LA)‐type chemistry of the larger rare‐earth metals. Representative monolanthanide examples of the type A′ and B′ include [(Tp t Bu,Me )La(=CH 2 )(AlMe 3 ) 2 ]11b and [(Tp t Bu,Me )Ln(=NAr)(AlHMe 2 )] (Ar = C 6 H 3 Me 2 ‐2,6) 12b. Spurred by the rich chemistry exhibited by Chen's scandium terminal imide complexes,9,17 we focused our efforts on the synthesis of the corresponding B ‐type imide complexes (of the larger rare‐earth elements).…”

Lanthanides and actinides: Annual survey of their organometallic chemistry covering the year 2013

“…The super-bulky hydrotris[3-tert-butyl-5-methylpyrazolyl] borate ligand Tp tBu,Me allowed the isolation of the heterometallic complexes (Tp tBu,Me )Ln[(-H)AlMe 3 ] 2 (Ln = Y, Lu), which could be transformed into the imido complexes (Tp tBu,Me )Ln[(-NC 6 H 3 Me 2 -2,6)(-H)AlMe 2 ] by subsequent reaction with 2,6-dimethylaniline according to Scheme 123 [108].…”

Reactivity of halfsandwich rare-earth metal methylaluminates toward potassium (2,4,6-tri-tert-butylphenyl)amide and 1-adamantylamine

“…9 Furthermore, complexes of the type Cp R Ln(AlMe 4 ) 2 were successfully applied in C-H bond activation protocols giving access to the first structurally characterized rare-earth metal methylidyne 10 and methylidene complexes. 13 One major finding was that the superbulky monanionic Tp tBu,Me (= hydrotris(3-tert-butyl-5-methyl-pyrazolyl)borate) ligand can afford monolanthanide derivatives of the type [(Tp tBu,Me )-Ln(NAr)(AlHMe 2 )] (Ar = C 6 H 3 Me 2 -2, 6) 14 and [(Tp tBu,Me )Ln(NR)-(AlMe 3 )] (Ln = Y, Ho; R = tBu, adamantyl). 13 One major finding was that the superbulky monanionic Tp tBu,Me (= hydrotris(3-tert-butyl-5-methyl-pyrazolyl)borate) ligand can afford monolanthanide derivatives of the type [(Tp tBu,Me )-Ln(NAr)(AlHMe 2 )] (Ar = C 6 H 3 Me 2 -2, 6) 14 and [(Tp tBu,Me )Ln(NR)-(AlMe 3 )] (Ln = Y, Ho; R = tBu, adamantyl).…”