Reaction of a bulky amine borane with lanthanide trialkyls. Formation of alkyl lanthanide imide complexes

Abstract

Lanthanide imidoborane complexes with terminal alkyl groups are synthesized from the reactions of simple lanthanide trialkyls with a bulky amine borane.

Pentamethylcyclopentadienyl-Supported Rare-Earth-Metal Benzyl, Amide, and Imide Complexes

“…Each yttrium center in 2a is formally 7-coordinated by a Cp* ligand, two thf molecules, and two imido ligands, adopting a four-legged piano-stool geometry. The Y–N imido bond lengths range from 2.222(4) Å to 2.304(4) Å (Table ), being comparable to the respective distances in the yttrium imide complexes [Cp′Y­(μ 3 -NCH 2 ­Ph)] 4 (Cp′ = η 5 -C 5 Me 4 ­SiMe 3 ) (2.193(3)–​2.342(3) Å) and [Y­(CH 2 ­SiMe 3 )­(μ 2 -NAr­BH 3 )] 2 (Ar = 2,6-(3,5-Me 2 C 6 H 3 ) 2 ­C 6 H 3 ) (2.297(2) and 2.335(2) Å). , The Lu–N bond lengths in formally 6-coordinate 2b (2.149(2)–​2.188(2) Å, Table ) are similar to those found in the dimeric imide complexes [{Bo M ­Cp tet }­LuNCH 2 ­(1-C 10 H 7 )] 2 (2.116(4)–2.163(4) Å) and [Lu­(AlMe 4 )­(NC 6 H 2 ­ t Bu 3 -2,4,6)] 2 (2.071–2.249 Å) but markedly elongated compared to the one in 5-coordinate terminal imide complex [(Tp t Bu,Me )­Lu­(=NC 6 H 3 ­(CF 3 ) 2 -3,5)­(DMAP)] (1.991(5) Å) . While the solid-state structure of compound 2a exhibits two thf molecules per yttrium center, one thf molecule is removed upon drying of a crystalline sample under reduced pressure, as evidenced by 1 H NMR spectroscopy.…”

“…Overall, the reaction of complexes of the type L LnR 2 ( L = bulky monoanionic anicillary ligand, R = alkyl, ,,− hydride) with a primary amine seems a most rational and viable approach to discrete rare-earth-metal imide complexes. Since rare-earth-metal ions have the tendency to assemble into stable di- or polynuclear complexes with bridging imido ligands, ,− such oligomerization can be counteracted by the use of bulky ancillary ligands, like β-diketiminato (nacnac) or tris­(pyrazolyl)­borato. , Moreover, bulky chelating ligands were shown to favorably stabilize the highly polarized LnNR bond. ,− Surprisingly, only a few fully characterized cyclopentadienyl-supported rare-earth-metal imide complexes have been described. Hessen and co-workers could isolate a scandium imide complex by insertion of benzonitrile into a Sc–diene bond (Chart , A ). , Another approach exploits the insertion of alkyl/​arylnitriles into the Ln–H bond of hydrides ( B ) …”

Catalytic Dehydrogenation of Dimethylamine Borane by Highly Active Thorium and Uranium Metallocene Complexes

“…Figure 2 shows the catalytic metrics for the most reactive Me 2 NH•BH 3 (6) dehydrogenation catalysts that have been reported in the literature. At ambient temperatures, (C 5 Me 5 ) 2 AnMe 2 (An = Th (1), U ( 2) 38 and shows better catalytic metrics than [Rh(1,5-cod)(μ-Cl)] 2 (8). 34 However, the rare-earth-metal complex, (C 5 H 5 BMe) 2 Y[CH-(SiMe 3 ) 2 ] (9), 39 exhibits higher TOFs, which may be attributed to the electron-withdrawing 1-methylboratabenzene ligand, since the electron-donating 1-triethylamineboratabenzene congener exhibited modest TOFs (9.4 h −1 ).…”

“…The study of amine borane (RR′HN·BH 3 ) dehydrogenation is a rich and comprehensive field that encompasses investigations using transition-metal, − main-group metal, , and lanthanide − catalysts. However, there has been one glaring omission: analogous chemistry with the actinides has been ignored.…”

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

“…Similarly, deprotonation of lanthanide anilide complexes was achieved via treatment with butyllithium, affording complexes of type IV [11]. A different synthesis approach has been employed in the reactions of alkyl complexes with amine-boranes to yield Lewis acid (LA)-stabilized imido entities [Ln(NR)(BH3)] (R = H, teraryl) [12,13]. [14], synthesis of substituted pyridines [15], preparation of Ln/M heterobimetallics [16], hydroelementation reactions [17], and polymerization of dienes [18].…”