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

Abstract

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)CHN [R = Bn, R' = Dipp (HL); R = Bn, R' = Bu (HL); R = CHOCH, R' = Dipp (HL); Dipp = PrCH] with MeSiCHLi or BuLi in hydrocarbon solvents (toluene or n-hexane) produced 1,3-disubstituted-2-indolyl lithium complexes [η:(μ-η:η)-1-Bn-3-(DippN═CH)CHNLi] (1), {[η:(μ-η:η:η)-1-Bn-3-(BuN═CH)CHN][η:η:(μ-η:η)-1-Bn-3-(BuN═CH)CHN][η:(μ-η:η)-1-Bn-3-(BuN═CH)CHN]Li} (2), and [η:η:(μ-η:η)-1-CHOCH-3-(DippN═CH)CHNLi] (3), respectively. The bonding modes of the indolyl ligand were kept in 1 by coordination with donor solvent, affording [η:(μ-η:η)-1-Bn-3-(DippN═CH)CHNLi(THF)] (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 [η:(μ-η:η)-1-Bn-3-(BuN═CH)CHNLi(THF)] (5). X-ray diffraction established that compounds 1, 3, 4, and 5 crystallized as dinuclear structures with the carbanionic sp carbon atoms of the indolyl ligands coordinated to lithium ions in a μ-η:η manner, while compound 2 crystallized as a trinuclear structure and the carbanionic atoms of the indolyl moieties coordinated to lithium ions in μ-η:η and μ-η:η:η manners. When the lithiation reaction of HL with 1 equiv of BuLi was carried out in THF, the monomeric lithium complex {η:η-1-Bn-3-(DippN═CH)-2-[1'-Bn-3'-(DippNCH)CHN]CHNLi(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 HL with a higher isolated yield. Accordingly, the lithium complexes [η:η-1-Bn-3-BuN═CH-2-(1'-Bn-3'-BuNCHCHN)CHNLi(L)] (L = THF, 7a; L = EtO, 7b) with the coupled indolyl moieties in η mode were isolated by treatment of HL with 2 in THF or EtO. All complexes were characterized by spectroscopic methods, and their structures were determined by X-ray diffraction study.

Halide-bridged tetranuclear organocopper(i) clusters supported by indolyl-based NCN pincer ligands and their catalytic activities towards the hydrophosphination of alkenes

“…In complexes 1a–2c , four copper ions formed a twisted triangular pyramid in which two halides capped the two surfaces of the triangular pyramid in μ 3 -X bonded to the three copper ions, and other two surfaces of the triangular pyramid were capped by two indolyl-based NCN pincer ligands in η 2 :κ 1 :κ 1 modes. The indolyl-based NCN pincer ligand was bonded to three individual metals in μ 3 -bridged mode, which was similar to that found in lithium complexes, 31,32 but different from that found in rare-earth metal chemistry. 31 The selected bond distances (Å) and angles (°) for complexes 1a–2c are listed in Table 2.…”

“…Dalton Transactions bonded to the three copper ions, and other two surfaces of the triangular pyramid were capped by two indolyl-based NCN pincer ligands in η 2 :κ 1 :κ 1 modes. The indolyl-based NCN pincer ligand was bonded to three individual metals in µ 3bridged mode, which was similar to that found in lithium complexes, 31,32 but different from that found in rare-earth metal chemistry. 31 The selected bond distances (Å) and angles (°) for complexes 1a-2c are listed in 67 Based on the above reason, µ 3 -Cl was not equally bonded to the three copper ions, with the Cu4-Cl1 distance (2.284(3) Å) and the Cu3-Cl2 distance (2.278(3) Å) being slightly shorter than those of the Cu2-Cl1, Cu3-Cl1, Cu1-Cl2, and Cu4-Cl2 bonds (2.631(3)-2.700(3) Å).…”

“…[24][25][26][27][28][29][30] We have reported a series of rare-earth metal complexes coordinated by indolyl ligands, which have a great effect on the structures of complexes and bonding modes of the ligands. [31][32][33][34] However, Cu(I) cluster complexes supported by pincer-type ligands bearing an electronrich indolyl motif have not been developed yet.…”

Noninnocent Behavior of a (3-Imino)indol-2-yl Ligand in Metal Complexes

“…(3-Imino)­indol-2-yl anions can be viewed as derivatives of the 4-alkenyl anions of but-2-en-1-imines. In recent years, some of us (Wang and Zhou) have found that these types of anions are useful C , N -chelating ligands for the preparation of lanthanide complexes that show high catalytic activity in isoprene polymerization. − Noting that transition-metal complexes of (3-imino)­indol-2-yl ligands are scarce, , we then initiated a study on 3d metal complexes of (3-imino)­indol-2-yl ligands. Herein, we wish to report the synthesis, characterization, and redox properties of iron complexes bearing (3-imino)­indol-2-yl ligands, which revealed that this type of C , N -chelating ligand is redox noninnocent.…”

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

“…In line with this high importance associated with the molecules of current topic, i.e., more than one indole molecule flanked by a central atom, conglomeration of the available synthetic methods will have a high scientific value. This review will give a concise account of the same, although preparations of ionic bis(indolyl) metal salts will not be considered [24][25][26][27][28][29][30][31][32][33].…”