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

The B(C6F5)3·H2O promoted synthesis of fluoroalkylated 3,3',3''-trisindolylmethanes from fluorocarboxylic acids and indoles

Trisindolylmethanes (TIMs) exist in many bioactive natural products and are frequently applied in medicinal chemistry and materials science. Herein, a simple and efficient protocol promoted by B(C₆F₅)₃·H₂O for the synthesis of their fluoroalkylated analogues, fluoroalkylated 3,3',3''-TIMs, is reported for the first time. Easily accessible fluorocarboxylic acids are utilized as the fluoroalkyl sources, exhibiting an obvious fluorine effect. This convenient and green process features mild and metal-free conditions, easy scale-up, and an environmentally friendly byproduct.

Molecular Main Group Metal Hydrides

This review serves to document advances in the synthesis, versatile bonding, and reactivity of molecular main group metal hydrides within Groups 1, 2, and 12-16. Particular attention will be given to the emerging use of said hydrides in the rapidly expanding field of Main Group element-mediated catalysis. While this review is comprehensive in nature, focus will be given to research appearing in the open literature since 2001.

Synthesis, Structures, and Solution Dynamics of Titanium and Zirconium Complexes Carrying a Bis(indolyl) and Two Diethylamido Ligands

Indolyl is the anionic species obtained from the deprotonation of the N-H group of indole. Group 4 transition-metal complexes that carry indolyl-based polydentate ligands represent promising homogeneous catalysts for, e.g., olefin polymerization, hydroamination, and nitrogen-fixation reactions due to the weak π-donation and electron-withdrawing properties, as well as the low basicity of indolyl. In this study, we systematically investigated the synthesis and structures of titanium and zirconium complexes that carry deprotonated 2,2'-bis(indolyl)methane ligands (henceforth: bis(indolyl) ligands) and two diethylamido ligands. We found that the coordination geometry of the indolyl nitrogen atom in such bis(indolyl) ligands is affected by the steric impact of the substituents attached to the central aromatic ring. Moreover, we examined the dynamics of such bis(indolyl) ligands in solution for the corresponding zirconium complexes, and the mechanism was discussed in conjunction with DFT calculations. The results of this study suggest that bis(indolyl) ligands may also serve as coordinatively flexible ancillary ligands, and indicate the feasibility of an expansion from bis(indolyl) to bis(indolyl)-donor ligands.

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

Four 2,2'-bisindolylmethanes (BIMs), a useful class of polyindolyl species joined to a central carbon, were synthesized using salicylaldehyde derivatives and simple acid catalysis; these are 2-[bis(3-methyl-1H-indol-2-yl)methyl]-6-methylphenol, (IIa), 2-[bis(3-methyl-1H-indol-2-yl)methyl]-4,6-dichlorophenol, (IIb), 2-[bis(3-methyl-1H-indol-2-yl)methyl]-4-nitrophenol, (IIc), and 2-[bis(3-methyl-1H-indol-2-yl)methyl]-4,6-di-tert-butylphenol, (IId). BIMs (IIa) and (IIb) were characterized crystallographically as the dimethyl sulfoxide (DMSO) disolvates, i.e. C₂₆H₂₄N₂O·2C₂H₆OS and C₂₅H₂₀Cl₂N₂O·2C₂H₆OS, respectively. Both form strikingly similar one-dimensional hydrogen-bonding chain motifs with the DMSO solvent molecules. BIM (IIa) packs into double layers of chains whose orientations alternate every double layer, while (IIb) forms more simply packed chains along the a axis. BIM (IIa) has a remarkably long c axis.

Reactivity of 1,3-Disubstituted Indoles with Lithium Compounds: Substituents and Solvents Effects on Coordination and Reactivity of Resulting 1,3-Disubstituted-2-Indolyl Lithium Complexes

Reactivity of 1,3-disubstituted indolyl compounds with lithium reagents was studied to reveal the substituents and solvent effects on coordination modes and reactivities resulting in different indolyl lithium complexes. Treatment of 1-alkyl-3-imino functionalized compounds 1-R-3-(R'N═CH)C₈H₅N [R = Bn, R' = Dipp (HL¹); R = Bn, R' = ^tBu (HL²); R = CH₃OCH₂, R' = Dipp (HL³); Dipp = ⁱPr₂C₆H₃] with Me₃SiCH₂Li or ⁿBuLi in hydrocarbon solvents (toluene or n-hexane) produced 1,3-disubstituted-2-indolyl lithium complexes [η¹:(μ₂-η¹:η¹)-1-Bn-3-(DippN═CH)C₈H₄NLi]₂ (1), {[η¹:(μ₃-η¹:η¹:η¹)-1-Bn-3-(^tBuN═CH)C₈H₄N][η²:η¹:(μ₂-η¹:η¹)-1-Bn-3-(^tBuN═CH)C₈H₄N][η¹:(μ₂-η¹:η¹)-1-Bn-3-(^tBuN═CH)C₈H₄N]Li₃} (2), and [η¹:η¹:(μ₂-η¹:η¹)-1-CH₃OCH₂-3-(DippN═CH)C₈H₄NLi]₂ (3), respectively. The bonding modes of the indolyl ligand were kept in 1 by coordination with donor solvent, affording [η¹:(μ₂-η¹:η¹)-1-Bn-3-(DippN═CH)C₈H₄NLi(THF)]₂ (4). The trinuclear complex 2 was converted to dinuclear form with a change of bonding modes of the indolyl ligand by treatment of 2 with donor solvent THF, producing [η¹:(μ₂-η¹:η¹)-1-Bn-3-(^tBuN═CH)C₈H₄NLi(THF)]₂ (5). X-ray diffraction established that compounds 1, 3, 4, and 5 crystallized as dinuclear structures with the carbanionic sp² carbon atoms of the indolyl ligands coordinated to lithium ions in a μ₂-η¹:η¹ manner, while compound 2 crystallized as a trinuclear structure and the carbanionic atoms of the indolyl moieties coordinated to lithium ions in μ₂-η¹:η¹ and μ₃-η¹:η¹:η¹ manners. When the lithiation reaction of HL¹ with 1 equiv of ⁿBuLi was carried out in THF, the monomeric lithium complex {η¹:η¹-1-Bn-3-(DippN═CH)-2-[1'-Bn-3'-(DippNCH)C₈H₅N]C₈H₄NLi(THF)} (6) having coupled indolyl moieties was obtained. The compound 6 can also be prepared by the reaction of 1 with 0.5 equiv of HL¹ with a higher isolated yield. Accordingly, the lithium complexes [η¹:η⁴-1-Bn-3-^tBuN═CH-2-(1'-Bn-3'-^tBuNCHC₈H₅N)C₈H₄NLi(L)] (L = THF, 7a; L = Et₂O, 7b) with the coupled indolyl moieties in η⁴ mode were isolated by treatment of HL² with 2 in THF or Et₂O. All complexes were characterized by spectroscopic methods, and their structures were determined by X-ray diffraction study.

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

The title compound, [Al(CH3)2(C13H17N2)] (systematic name; {2-[(di-ethyl-amino)-meth-yl]indol-1-yl-κ(2) N,N'}di-methyl-aluminium), was prepared by methane elimination from the reaction of 2-(di-ethyl-amino-meth-yl)indole and tri-methyl-aluminium. The complex crystallizes readily from a concentrated toluene solution in high yield. The asymmetric unit contains two crystallographically independent mol-ecules. Each mol-ecule has a four-coordinate aluminium atom that has pseudo-tetra-hedral geometry. C-H⋯π inter-actions link the independent mol-ecules into chains extending along the b-axis direction.