Confirmation of Bridging N-Indolides in 3-Methylindole and Di- and Tri(3-methylindolyl)methane Complexes of Dimethyl-, Diethyl-, and Diisobutylaluminum

Abstract

Reactions of 3-methylindole with one equivalent of R 3 Al produce the N-indolide-bridged dimers ). NMR spectroscopy ( 1 H, 13 C) demonstrates that compounds 3a, 3b, and 3c each exist in solution as a mixture of interconverting syn and anti isomers. Reactions of di(3-methylindolyl)methane or tri(3-methylindolyl)methane with one equivalent of Me 3 Al or Et 3 Al similarly produce the N-indolide-bridged compounds [(Ph)HC(3-CH 3 C 8 H 4 NAlR 2 ) 2 ] (R = Me (4)) or [HC(3-CH 3 C 8 H 4 NAlR 2 ) 3 ] (R =Me (5a), Et (5b)), respectively. Reaction of tri(3-methyl-2-indolyl)methane with one equivalent of i Bu 3 Al yielded the N-indolide-bridged compound [HC(3-CH 3 C 8 H 4 NAl i Bu 2 ) 2 (3-CH 3 C 8 H 4 NAl(H) i Bu)] ( 6), apparently the result of β-hydrogen elimination of isobutene from one isobutyl group per complex. The molecular structures of compounds 3a, 4, and 5a were determined by X-ray crystallography. Crystallographic data confirmed the presence of μ 2 -η 1 :η 1 -N-3-methylindolide groups in each compound, the first examples of bridging N-indolide groups in compounds of the group 13 elements.

Molecular Main Group Metal Hydrides

“…As with carbon-supported aluminum hydride systems, a common reactivity pathway is the hydroalumination of organic π-bonds. Given the plethora of new N -donor aluminum hydride systems reported in the past two decades, ,− this section will aim to focus on the new bonding motifs and reactivity pathways uncovered in this area.…”

“…The active catalyst is thought to be the in situ generated aluminum hydride {(κ 2 -H 2 B­(NMe 2 ) 2 } 2 AlH ( 722 ), featuring a pair of chelating [H 2 B­(NMe 2 ) 2 ] − ligands, themselves derived from trapping of a [Me 2 NBH 2 ] monomer unit by an Al–NMe 2 moiety (Scheme ). The use of Al­(NMe 2 ) 3 (or its gallium analogue) or Al­(N i Pr 2 ) 3 to catalyze the dehydrocoupling of i Pr 2 NH·BH 3 and t BuNH 2 ·BH 3 has also been reported . In this case the products are the monomeric amidoborane i Pr 2 NBH 2 and the borazine derivative [ t BuNBH] 3 , respectively, mimicking the results seen with single-site Rh­(I) catalysts.…”

Synthesis, characterization and crystal structure of a 2-(diethylaminomethyl)indole ligated dimethylaluminium complex

“…Neither of these sets of hits included structures involving indolyl moieties bound to aluminium. A substructure search for N-bound indolylcoordinating aluminium complexes resulted in only five hits (Kingsley et al, 2010), all of which contained bridging 2 : 1 : 1 coordination modes. The title compound is the first structurally characterized complex with a monomeric 1 : 1coordinating indole moiety to aluminium.…”

“…The reaction solution turned bright yellow, which darkened as the solution was stirred for 12 h. The solvent was then removed in vacuo resulting in a yellow solid, which was dissolved in a mixture of 10 mL of hot toluene, followed by cooling to 243 K for 48 h. J HH = 7.8 Hz, 1H, H15), 7.00 (t, 3 J HH = 7.8 Hz, 1H, H14), 6.31 (s, 1H, H11), 4.00 (s, 2H, indole CH 2 ), 2.88 (q, 3 J HH = 7.2 Hz, 4H, amino CH 2 CH 3 ), 1.13 (t, 3 J HH = 7.2 Hz, 6H, amino CH 2 CH 3 ), À0.59 (s, 6H, AlCH 3 ). 13 C{ 1 H} NMR (CDCl 3 , 150.8 MHz): 141.7 (C17), 139.4 (C10), 131.8 (C12), 120.2 (C15), 119.6 (C16), 118.5 (C15), 113.7 (C14), 98.1 (C11), 53.2 (indole CH 2 ), 44.7 (amino CH 2 CH 3 ), 8.3 (amino CH 2 CH 3 ), À11.10 (br, AlCH 3 ) (Kingsley et al, 2010). Analysis calculated for C 15 H 23 N 2 Al: C,69.74;H,8.97;N,10.84.…”

Synthesis and crystal structures of some bis(3-methyl-1H-indol-2-yl)(salicyl)methanes

“…Recently, 2,2 0 ,2 00 -TIMs [see (b) in Scheme 1] and 2,2 0 -BIMs [see (c) in Scheme 1] have attracted greater interest because of their potential as ligands (Mason, 2003;Bakthadoss et al, 2015). Structural data has been reported for poly(indol-2-yl)methanes bonded through the indole N atom to main-group elements from group 13 (B, Al, and Ga) (Fneich et al, 2018;Song et al, 2012;Kingsley et al, 2010), group 14 (Si) (Mason, 2003), and group 15 (P and Sb) (Mason, 2003;Mallov et al, 2012). Similar bonding patterns have been reported for group 4 metals (Ti and Zr) (Mason, Fneich et al, 2003;Mason, 2003;Mason et al, 2005).…”