Indolyl Ligands Research Articles

Synthesis and Characterization of Rare-Earth Metal Complexes Bearing a 2-N,N-Dimethylamino-Ethylene-Imino-Functionalized Indolyl Ligand and Their Catalytic Activities Toward Hydrosilylation of Imines

The reactions of 2-N,N-dimethylamino-ethylene-imino-functionalized indolyl proligand 2-(Me2NCH2CH2N = CH)C8H5NH (HL) with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 in toluene afforded a series of rare-earth metal amido complexes [κ3-(N,N,N)-2-(Me2NCH2CH2N = CH)C8H5N]RE[N(SiMe3)2]2 (RE = Y (1a), Nd (1b), Sm (1c), Gd (1d), Dy (1e), Er (1f), and Yb (1g)). While the reaction of HL with [(Me3Si)2N]3Eu(μ-Cl)Li(THF)3 produced the europium(II) complex in a dimeric form [{(η5-μ-η1:η1:η1)-2-(Me2NCH2CH2N═CH)C8H5N}Eu{N(SiMe3)2}]2 (2), which is believed to have happened through the homolysis of the Eu–N bond. Further reaction of complex 1a with PhCH═NPh provided an unexpected rare-earth metal complex [κ2-(N,N)-PhN{PhCH(CH2SiMe2)}N(SiMe3)]YL (7) through the sp3 C–H bond activation of the methyl on the silicon atom to form a Y–C bond followed by the insertion of the C═N bond of the imine PhCH═NPh to form an amido group connected to the central metal. All complexes were characterized by spectroscopic methods, elemental analyses, and single-crystal X-ray diffraction, and complexes 1a–1c and 7 were additionally characterized by NMR spectroscopy. The catalytic performance of complexes 1a–1g for the hydrosilylation of imines was investigated, and the catalytic mechanism was proposed based on the experimental results.

Synthesis of rare-earth metal bisalkyl complexes supported by [1-(2-N-morpholinoethylene)-3-(4,4-dimethyl-2-oxazolinyl)] indolyl ligand and their application in the intermolecular hydrophosphination of aryl alkenes

Well-defined N-protected 3‑oxazolinyl functionalized indolyl rare-earth metal bisalkyl complexes LRE(CH2SiMe3)2(DME), (L = 1-(2-N-morpholinoethylene)-3-(4,4-dimethyl-2-oxazolinyl) indolyl, RE = Y (1a), Yb (1b), Er (1c), Dy (1d), Gd (1e), DME = 1,2-dimethoxyethane) have been synthesized and characterized. The complexes were coordinated by the 2‑indolyl sp2 carbanion, N atom of oxazolinyl, two alkyl groups and two oxygen atoms of DME. They performed high catalytic activities in the intermolecular hydrophosphination of various styrene derivatives and demonstrated exclusive regiospecificity affording the anti-Markovnikov addition products. The catalysts could promote hydrophosphination of bulky alkenes such as naphthalene ethylene under relatively mild conditions.

Synthesis and characterization of rare-earth metallate amido complexes bearing the 2-amidate-functionalized indolyl ligand and their application in the hydroboration of esters with pinacolborane.

The reactions of 2-amidate-functionalized indolyl proligand 2-(2,6-iPr2C6H3NHCO)C8H5NH (H2L) with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 were studied leading to the synthesis and characterization of a series of novel discrete trinuclear rare-earth metallate amido complexes containing the anion [{η1:(μ2-η1:η1):η1-LREN(SiMe3)2}3(μ3-Cl)]- and cation Li+(THF)4 (RE = Y(1a), Nd (1b), Sm (1c), Gd (1d), Dy (1e), Er (1f), and Yb (1g)) in good yields by silylamine elimination. All of the complexes were characterized by spectroscopic methods, elemental analyses and single-crystal X-ray diffraction, and complexes 1a and 1c were additionally characterized by NMR spectroscopy. As proof of principle of their activity, these complexes were used as precatalysts for the hydroboration of esters using HBpin as the hydride source displaying high activity under neat and room temperature conditions. As a result, the ligand, ionic and multinuclear cooperative effects on catalytic activity were observed.

Synthesis, Characterization, and Catalytic Application of Palladium Complexes Containing Indolyl-NNN-Type Ligands.

In this study, a series of N-heterocyclic indolyl ligand precursors 2-Py-Py-IndH, 2-Py-Pz-IndH, 2-Py-7-Py-IndH, 2-Py-7-Pz-IndH, and 2-Ox-7-Py-IndH (L1H-L5H) were prepared. The treatment of ligand precursors with 1 equivalent of palladium acetate affords palladium complexes 1–5. All ligand precursors and palladium complexes were characterized by NMR spectroscopy and elemental analysis. The molecular structures of complexes 3 and 5 were determined by single crystal X-ray diffraction techniques. The application of those palladium complexes 1–5 to the Suzuki reaction with aryl halide substrates was examined.

Synthesis, structure and catalytic activity of rare-earth metal amino complexes incorporating imino-functionalized indolyl ligand

The reactions of the imino-functionalized indolyl ligand (HL, L = 3-(4-Me2N-C6H4CH=N-CH2CH2)C8H5N) with the rare-earth metal amides [(Me3Si)2N]3RE(µ-Cl)Li(THF)3 producing different types of rare-earth metal amido complexes were investigated. The reactions of HL with 1 equiv. of [(Me3Si)2N]3RE(µ-Cl)Li(THF)3 generated a series of hetero-nuclear bimetallic rare-earth metal amino complexes {[η1:µ-η2-3-(4-Me2N-C6H4CH=N-CH2CH2)C8H5]RE[N(SiMe3)2]2(µ-Cl)Li(THF)} (RE = Y(1), Sm(2), Gd(3), Er(4), Yb(5)). By extending the reaction time, only the reaction of HL with [(Me3Si)2N]3Gd(µ-Cl)Li(THF)3 gave an unexpected binuclear rare-earth metal complex {[(µ-η5:η1):η1:η1-3-[(Me2N)2-C14H9]-(NCH2CH2-C8H5N)2]Gd2[N(SiMe3)2]3} (6) incorporating a novel polycyclic ligand through C-C and C-N coupling. Treatment of HL with [(Me3Si)2N]3Sm(µ-Cl)Li(THF)3 in a 2:1 ratio generated the bis(indolyl) heteronuclear bimetallic rare-earth metal amino complex {(η1:η1-[µ-η2:η1-3-(4-Me2N-C6H4CH=N-CH2CH2)C8H5]Li[µ-η2:η1-3-(4-Me2N-C6H4CH=N-CH2CH2)C8H5])Sm[N(SiMe3)2]2} (7) in low yield probably due to accompanying with the formation of the complex 2. The above results indicated that reaction conditions play important roles in the formation of different coordination modes of the imino-functionalized indolyl rare-earth metal amido complexes. All new complexes 1−7 are fully characterized including X-ray structural determination. The catalytic activity of complexes 1-7 for the addition of amines to carbodiimides was explored. The results showed that all complexes displayed an excellent activity towards the addition of amines to carbodiimides producing guanidine under solvent-free condition.

Cis-1,4-Polymerization of isoprene catalyzed by rare-earth metal amido complexes supported by 2-t-butylimino- or 2-amino-functionalized indolyl ligand

Aiming at developing highly efficient and more conveniently treated rare-earth metal catalyst systems, the performance of a series of the rare-earth metal amido complexes bearing 2-t-butylimino- or 2-amino-functionalized indolyl ligands as precatalysts toward isoprene polymerization was investigated. Under the activation of borate activator [Ph3C][B(C6F5)4] and AlR3, the monomeric bis(amido) complexes [2-(tBuN = CH)C8H5N]RE[N(SiMe3)2]2 (RE = Er (1), Y (2), Sm (3), Nd (4)) and the dinuclear complex {[µ-η5:η1:η1-2-(2,6-iPr2C6H3NCH2)C8H5N]Nd[N(SiMe3)2]}2 (5) exhibit different catalytic activities and cis-1,4-selectivities for isoprene polymerization depending on cocatalysts of aluminum alkyls, central rare-earth metals and the solvents. Among them, the homogeneous ternary system Nd complex 4 or 5/ [Ph3C][B(C6F5)4]/AliBu3 could very efficiently catalyze polymerization of isoprene under the relatively mild conditions to afford the cis-1,4-polyisoprenes (up to 98.3%) with high number-average molecular weights and narrow to moderate molecular weight distributions.

Synthesis, characterization, and reactivity of dinuclear organo-rare-earth-metal alkyl complexes supported by 2-amidate-functionalized indolyl ligands: substituent effects on coordination and reactivity.

Two series of new dinuclear organo-rare-earth-metal alkyl complexes supported by 2-amidate-functionalized indolyl ligands with different haptic modes were synthesized and characterized. The treatment of [RE(CH2SiMe3)3(THF)2] with 1 equiv. of 2-(2,6-iPr2C6H3NHC[double bond, length as m-dash]O)C8H5NH (H2L1) and 2-(2-tBuC6H4NHC[double bond, length as m-dash]O)C8H5NH (H2L2) in toluene yielded the dinuclear organo-rare-earth-metal alkyl complexes {[η1:(μ2-η1:η1)-L1]RE(CH2SiMe3)(THF)2}2 [RE = Gd (1a), Dy (1b), Y (1c), Er (1d), and Yb (1e)] and {[η1:(μ2-η1:η1):η1-L2]RE(CH2SiMe3)(THF)2}2 [RE = Gd (2a), Dy (2b), Y (2c), Er (2d), and Yb (2e)] in good yields. When [RE(CH2SiMe3)3(THF)2] were treated with 2 equiv. of H2L1 or H2L2 in THF, the dinuclear organo-rare-earth-metal complexes {(η1:η1-HL)[η1:(μ2-η1:η1):η1-L]RE(THF)}2 (1ca: RE = Y, L = L1; 2ea: RE = Yb, L = L2) were obtained. The complexes could react with small organic molecules such as N,N'-diisopropylcarbodiimide (DIC), phenyl isocyanate, N-methylallylamine, phenylacetylene, pyridine, N-phenylimidazole, or 4-dimethylaminopyridine (DMAP) to yield a series of new complexes with different reactivity patterns along with the reported rare-earth-metal alkyl complexes. In the presence of cocatalysts, these dinuclear organo-rare-earth-metal alkyl complexes could initiate isoprene polymerization with high activity (100% conversion of 2000 equiv. of isoprene in 12 h), yielding polymers with high regioselectivity (1,4 polymers up to 96.1%).

Synthesis and Characterization of Rare-Earth Metal Complexes Supported by 2-Imino or Amino Appended Indolyl Ligands with Diverse Hapticities: Tunable Selective Catalysis for Isoprene Polymerization

The reaction of 2-(2,6-DippNHCH2)C8H5NH (Dipp = 2,6-iPrC6H3, C8H5NH = indolyl) with 1 equiv of (Me3SiCH2)3Yb(THF)2 at room temperature generated mononuclear ytterbium complex 1 having the indolyl ligands in η1:η1 mode with reduction of Yb3+ to Yb2+ and oxidation of the amino to imino group. In the case of Er and Y, the reactions produced dinuclear complexes 2 and 3 having the indolyl ligands in μ-η2:η2:η1 modes with the central metals. When the rare-earth metal is dysprosium, the reaction afforded mixed ligated dinuclear complex 4a having indolyl ligands in μ-η5:η1:η1 and μ-η6:η1:η1 modes with Dy, and its isomer 4b having the indolyl ligands only in μ-η5:η1:η1 modes with Dy. However, when the rare-earth metal is Gd, the reaction only produced the mixed ligated dinuclear gadolinium complex [(μ-η5:η1:η1)-2-(2,6-DippNCH2)Ind(μ-η6:η1:η1)-2-(2,6-DippNCH2)Ind][Gd(CH2SiMe3)(thf)]2 (5), having indolyl ligands in μ-η5:η1:η1 and μ-η6:η1:η1 modes with Gd. In addition, treatment of 2-(2,6-DippNHCH2)C8H5NH with 1.25 e...

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.

Di and trinuclear rare-earth metal complexes supported by 3-amido appended indolyl ligands: synthesis, characterization and catalytic activity towards isoprene 1,4-cis polymerization.

Different di and trinuclear rare-earth metal complexes supported by 3-amido appended indolyl ligands were synthesized and their catalytic activities towards isoprene polymerization were investigated. Treatment of [RE(CH2SiMe3)3(thf)2] with 1 equiv. of 3-(CyN[double bond, length as m-dash]CH)C8H5NH in toluene or in THF afforded dinuclear rare-earth metal alkyl complexes having indolyl ligands in different hapticities with central metals {[η2:η1-μ-η1-3-(CyNCH(CH2SiMe3))Ind]RE-(thf)(CH2SiMe3)}2 (Cy = cyclohexyl, Ind = Indolyl, RE = Yb (1), Er (2), Y (3)) or {[η1-μ-η1-3-(CyNCH(CH2SiMe3))Ind]RE-(thf)2(CH2SiMe3)}2 (RE = Yb (4), Er (5), Y (6), Gd (7)), respectively. These two series of dinuclear complexes could be transferred to each other easily by only changing the solvents in the process. Reaction of [Er(CH2SiMe3)3(thf)2] with 1 equiv. of 3-t-butylaminomethylindole 3-(tBuNHCH2)C8H5NH in THF afforded the unexpected trinuclear erbium alkyl complex [η2:η1-μ-η1-3-(tBuNCH2)Ind]4Er3(thf)5(CH2SiMe3) (8), which can also be prepared by reaction of 3 equiv. of [Er(CH2SiMe3)3(thf)2] with 4 equiv. of 3-(tBuNHCH2)C8H5NH in THF. Accordingly, complexes [η2:η1-μ-η1-3-(tBuNCH2)Ind]4RE3(thf)5(CH2SiMe3) (RE = Y (9), Dy (10)) were prepared by reactions of 3 equiv. of [RE(CH2SiMe3)3(thf)2] with 4 equiv. of 3-(tBuNHCH2)C8H5NH in THF. Reactions of [RE(CH2SiMe3)3(thf)2] with 1 equiv. of 3-t-butylaminomethylindole 3-(tBuNHCH2)C8H5NH in THF, followed by treatment with 1 equiv. of [(2,6-iPr2C6H3)N[double bond, length as m-dash]CHNH(C6H3iPr2-2,6)] afforded, after workup, the dinuclear rare-earth metal complexes [η1-μ-η1:η1-3-(tBuNCH2)Ind][η1-μ-η1:η3-3-(tBuNCH2)Ind]RE2(thf)[(η3-2,6-iPr2C6H3)NCHN(C6H3iPr2-2,6)]2(RE = Er (11), Y (12)) having the indolyl ligands bonded with the rare-earth metal in different ligations. All new complexes 1-12 were fully characterized by spectroscopic methods and elemental analyses, and their structures were determined by X-ray crystallographic analyses. It was found that, except for complexes 1, 4, 11 and 12, all complexes were highly efficient catalysts for selective isoprene polymerization (up to 99% 1,4-cis selectivity) with the cooperation of co-catalysts, and the trinuclear complexes displayed advantages over dinuclear complexes in terms of molecular weight of polymers.

Crystal structure of aceto-nitrile-[η(6)-1-methyl-4-(1-methyl-eth-yl)benzene][1-(pyrimidin-2-yl)-3H-indol-1-ium-2-yl-κ(2) N,C]ruthenium(II) bis-(hexa-fluorido-anti-monate).

In the title compound, [Ru(C10H14)(C12H9N3)(CH3CN)][SbF6]2, the ruthenium(II) cation is η (6)-coordinated by the para-cymene ligand with a Ru-centroid(η (6)-benzene) distance of 1.746 (2) Å. Furthermore, ruthenium coordinations to the C and N atoms of the pyrimidyl indole ligand are found to be 1.986 (4) and 2.082 (3) Å, respectively. The typical piano-stool coordination environment is saturated with an aceto-nitrile solvent mol-ecule with a Ru-N distance of 2.044 (3) Å. The indolyl ligand is protonated at the C3 position with the N=C imine bond length appropriate to that of related 3H-indole-based complexes. In the crystal, the complex cation is linked to the SbF6 (-) ions through weak C-H⋯F hydrogen bonds.

Synthesis and Reactivity of Rare-Earth-Metal Monoalkyl Complexes Supported by Bidentate Indolyl Ligands and Their High Performance in Isoprene 1,4-cis Polymerization

A series of novel rare-earth-metal monoalkyl complexes incorporating partially rotation restricted [N,N]-bidentate indolyl ligands were synthesized and characterized, and their reactivities and catalytic activities were investigated. Treatment of [RE(CH2SiMe3)3(thf)2] with 1 equiv of 2-[(N-2,6-diisopropylphenyl)iminomethyl)]indole (2-(2,6-iPr2C6H3N═CH)C8H5NH) in toluene at room temperature afforded the rare-earth-metal monoalkyl complexes [η1:η1-2-(2,6-iPr2C6H3N═CH)Ind]2RE(CH2SiMe3)(thf) (Ind = indolyl; RE = Yb (1), Er (2), Y (3), Dy (4), Gd (5)) and the samarium complex [η1:η1-2-(2,6-iPr2C6H3N═CH)Ind]3Sm (6) via alkane elimination in good yields. Treatment of complex 2 or 3 with 1 equiv of PhSiH3 in toluene at 80 °C for 12 h afforded the dinuclear complexes {[μ-η6:η1:η1-2-(2,6-iPr2C6H3NCH2)Ind]RE[2-(2,6-iPr2C6H3N═CH)Ind]}2 (Ind = indolyl, RE = Er (7), Y (8)) in good isolated yields. Treatment of complex 2 or 3 with 1 equiv of amidine (2,6-iPr2C6H3)N═CHNH(2,6-iPr2C6H3) in toluene produced the correspondin...

Synthesis and Characterization of Organo-Rare-Earth Metal Monoalkyl Complexes Supported by Carbon σ-Bonded Indolyl Ligands: High Specific Isoprene 1,4-Cis Polymerization Catalysts

A series of N-protected 3-imino-functionalized indolyl ligands 1-R-3-(R'N═CH)C8H5N [R = Bn, R' = 2,6-(i)Pr2C6H3 (HL(1)); R = CH3, R' = 2,6-(i)Pr2C6H3 (HL(2)); R = Bn, R' = (t)Bu (HL(3))] and 1-CH3-2-(2,6-(i)Pr2C6H3N═CH)C8H5N (HL(4)) was prepared via reactions of N-protected indolyl aldehydes with corresponding amines. The C-H σ-bond metathesis followed by alkane elimination reactions between RE(CH2SiMe3)3(thf)2 and HL(1)-HL(3) afforded the carbon σ-bonded indolyl-ligated rare-earth metal monoalkyl complexes. Reactions of RE(CH2SiMe3)3(thf)2 with 2 equiv of HL(1) or HL(2) gave the carbon σ-bonded indolyl-ligated rare-earth metal monoalkyl complexes L(1)2RECH2SiMe3 (RE = Y(1), Er(2), Dy(3)) and L(2)2RECH2SiMe3 (RE = Y(5), Er(6), Dy(7), Yb(8)), while reaction of Yb(CH2SiMe3)3(thf)2 with 2 equiv of HL(1) afforded the ytterbium dialkyl complex L(1)Yb(CH2SiMe3)2(thf)2 (4). Reactions of RE(CH2SiMe3)3(thf)2 with HL(3) gave the tris(heteroaryl) rare-earth metal complexes L(3)3RE (RE = Y(9), Er(10)). In the presence of cocatalysts, the rare-earth metal monoalkyl complexes initiated isoprene polymerization with a high activity (90% conversion of 1000 equiv of isoprene in 25 min) producing polymers with high regio- and stereoselectivity (1,4-cis polymers up to 99%).

Reactivity of functionalized indoles with rare-earth metal amides. Synthesis, characterization and catalytic activity of rare-earth metal complexes incorporating indolyl ligands.

The reactivity of several functionalized indoles 2-(RNHCH2)C8H5NH (R = C6H5 (1), (t)Bu (2), 2,6-(i)Pr2C6H3 (3)) with rare-earth metal amides is described. Reactions of 1 or 2 with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 (RE = Eu, Yb) respectively produced the europium complexes [2-(C6H5N[double bond, length as m-dash]CH)C8H5N]2Eu[N(SiMe3)2] (4) and [2-((t)BuN[double bond, length as m-dash]CH)C8H5N]Eu[N(SiMe3)2]2 (5), and the ytterbium complex [2-((t)BuN[double bond, length as m-dash]CH)C8H5N]2Yb[N(SiMe3)2] (6), containing bidentate anionic indolyl ligands via dehydrogenation of the amine to the imine. In contrast, reactions of the more sterically bulky indole 3 with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 afforded complexes [2-(2,6-(i)Pr2C6H3NCH2)C8H5N]RE[N(SiMe3)2](THF)2 (RE = Yb (7), Y (8), Er (9), Dy (10)) with the deprotonated indolyl ligand. While reactions of 3 with yttrium and ytterbium amides in refluxing toluene respectively gave the complexes [2-(2,6-(i)Pr2C6H3N[double bond, length as m-dash]CH)C8H5N]3Y (11) and [2-(2,6-(i)Pr2C6H3N[double bond, length as m-dash]CH)C8H5N]2Yb(II)(THF)2 (12), along with transformation of the amino group to the imino group, and also with a reduction of Yb(3+) to Yb(2+) in the formation of 12. Reactions of 3 with samarium and neodymium amides provided novel dinuclear complexes {[μ-η(5):η(1):η(1)-2-(2,6-(i)Pr2C6H3NCH2)C8H5N]RE[N(SiMe3)2]}2 (RE = Sm (13), Nd (14)) having indolyl ligands in μ-η(5):η(1):η(1) hapticities. The pathway for the transformation of the amino group to the imino group is proposed on the basis of the experimental results. The new complexes displayed excellent activity in the intramolecular hydroamination of aminoalkenes.

Dinuclear rare-earth metal alkyl complexes supported by indolyl ligands in μ-η(2) :η(1) :η(1) hapticities and their high catalytic activity for isoprene 1,4-cis-polymerization.

Two series of new dinuclear rare-earth metal alkyl complexes supported by indolyl ligands in novel μ-η(2) :η(1) :η(1) hapticities are synthesized and characterized. Treatment of [RE(CH2 SiMe3 )3 (thf)2 ] with 1 equivalent of 3-(tBuN=CH)C8 H5 NH (L1 ) in THF gives the dinuclear rare-earth metal alkyl complexes trans-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH(CH2 SiMe3 )}Ind)RE(thf)(CH2 SiMe3 )]2 (Ind=indolyl, RE=Y, Dy, or Yb) in good yields. In the process, the indole unit of L1 is deprotonated by the metal alkyl species and the imino C=N group is transferred to the amido group by alkyl CH2 SiMe3 insertion, affording a new dianionic ligand that bridges two metal alkyl units in μ-η(2) :η(1) :η(1) bonding modes, forming the dinuclear rare-earth metal alkyl complexes. When L1 is reduced to 3-(tBuNHCH2 )C8 H5 NH (L2 ), the reaction of [Yb(CH2 SiMe3 )3 (thf)2 ] with 1 equivalent of L2 in THF, interestingly, generated the trans-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH2 }Ind)Yb(thf)(CH2 SiMe3 )]2 (major) and cis-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH2 }Ind)Yb(thf)(CH2 SiMe3 )]2 (minor) complexes. The catalytic activities of these dinuclear rare-earth metal alkyl complexes for isoprene polymerization were investigated; the yttrium and dysprosium complexes exhibited high catalytic activities and high regio- and stereoselectivities for isoprene 1,4-cis-polymerization.

Synthesis, structure, and catalytic activity of rare-earth metal amides with a neutral pyrrolyl-functionalized indolyl ligand

The reactions of neutral pyrrolyl-functionalized indole with rare-earth metal amides [(Me3Si)2N]3RE(µ-Cl)Li(THF)3 produced the rare-earth metal complexes [(Me3Si)2N]2RE([η1:µ-η2-3-(2-(N-CH3)C4H3NCH=N-CH2CH2)C8H5N])(µ-Cl)Li(THF) (RE = Er, Y) having indolyl ligand η1 bonded to rare-earth metal ion and η2 bonded to lithium ion. The catalytic activities of these lanthanide amido complexes for addition of terminal alkynes to aromatic nitriles were explored. Results reveal that these complexes displayed a good catalytic activity for the addition reaction under mild conditions.

Synthesis, structure, and catalytic activity of novel trinuclear rare-earth metal amido complexes incorporating μ–η5:η1bonding indolyl and μ3-oxo groups

The reactions of different pyrrolyl-functionalized indoles with rare-earth metal(III) amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Er, Dy, Eu, Y) produced different kinds of rare-earth metal amido complexes. Reactions of N-((1H-pyrrol-2-yl)methylene)-2-(1H-indol-3-yl)ethanamine with rare-earth metal amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Er, Dy, Eu, Y) in toluene or THF at temperatures of 75-80 °C afforded the novel trinuclear rare-earth metal amido complexes incorporating the indolyl ligand in μ-η(5):η(1) bonding modes and a μ3-O group, which is believed to originate from cleavage of the THF ring based on experimental results. Reactions of 2-(1H-indol-3-yl)-N-((1-methyl-1H-pyrrol-2-yl)methylene)ethanamine with rare-earth metal(III) amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Dy) produced mononuclear ytterbium and dysprosium amides having the indolyl ligand in an η(1) bonding fashion. The results indicate that substituents not only have an influence on reactivity, but also have an influence on the bonding of the indolyl ligands with metals. The catalytic activities of the novel lanthanide amido complexes for the hydrophosphonylation of both aromatic and aliphatic aldehydes and ketones were explored. The results indicate that these complexes display a high catalytic activity for the C-P bond formation under mild conditions when using low catalyst loadings (0.1 mol% for aldehydes and ketones). Thus, it provides a potential way to prepare α-hydroxy phosphonates.

Synthesis, Structure, and Reactivity of Lanthanide Complexes Incorporating Indolyl Ligands in Novel Hapticities

The chemistry of interactions of 2-(2,6-diisopropylphenylaminomethylene)indole ligand (1) with europium and ytterbium amides is described. Reaction of 2-(2,6-diisopropylphenylaminomethylene)indole 2-(2,6-i-Pr2C6H3NHCH2)C8H5NH (1) with europium amide [(Me3Si)2N]3Eu(III)(μ-Cl)Li(THF)3 afforded a novel europium(II) complex formulated as {[μ-η(6):η(1):η(1)-2-(2,6-i-Pr2C6H3N═CH)C8H5N]Eu[2-(2,6-i-Pr2C6H3N═CH)C8H5N]}2 (2), having a bridged indolyl ligand in the novel μ-η(6):η(1):η(1) hapticities with the reduction of europium(III) to europium(II) and the oxidation of amino to imino group. Reaction of 2-(2,6-diisopropylphenylaminomethylene)indole 2-(2,6-i-Pr2C6H3NHCH2)C8H5NH (1) with ytterbium(III) amide [(Me3Si)2N]3Yb(III)(μ-Cl)Li(THF)3 produced the only deprotonated ytterbium(III) complex formulated as [2-(2,6-i-Pr2C6H3NCH2)C8H5N]Yb[N(SiMe3)2](THF)2 (3), having an η(1) hapticity indolyl ligand. Reaction of 2 with formamidine [(2,6-Me2C6H3)NCHNH(C6H3Me2-2,6)] produced {[μ-η(3):η(1):η(1)-2-(2,6-i-Pr2C6H3N═CH)C8H5N]Eu[(2,6-Me2C6H3)NCHN(C6H3Me2-2,6)](THF)}2 (4), which has a bridged indolyl ligand in the novel μ-η(3):η(1):η(1) hapticities, whereas the reaction of 2 with the more sterically bulky formamidine [(2,6-i-Pr2C6H3)NCHNH(C6H3i-Pr2-2,6)] afforded complex {[μ-η(2):η(1):η(1)-2-(2,6-i-Pr2C6H3N═CH)C8H5N]Eu[(2,6-i-Pr2C6H3)N═CHN(C6H3i-Pr2-2,6)](THF)}2 (5), having the indolyl ligand in the novel μ-η(2):η(1):η(1) hapticities. The results represent the first example of organometallic complexes having indolyl ligands in the novel μ-η(6):η(1):η(1), μ-η(3):η(1):η(1), and μ-η(2):η(1):η(1) bonding modes with metal.

{2-[Bis(3-methyl-1H-indol-2-yl)meth-yl]phenolato-κO}dimeth-yl(tetra-hydro-furan-κO)aluminium(III).

The title compound, [Al(CH3)2(C25H21N2O)(C4H8O)], was isolated as a minor component from a reaction mixture of the parent indolyl ligand and trimethyl­aluminum in tetra­hydro­furan. The ligands adopt a distorted tetra­hedral geometry around aluminium. Obvious hydrogen-bonding interactions are not present.

Reactive Indolyl Complexes of Group 9 Metals

A series of novel indolyl−imine ligand precursors have been synthesized. In particular, bidentate, tridentate, and potentially tetradentate ligands were prepared, each containing both indolyl sp2-N and imine sp2-N donors. A series of neutral rhodium(I) and iridium(I) complexes of these ligands were synthesized, including monometallic and bimetallic complexes. The X-ray structures of three of the monometallic complexes with bidentate indolyl−imine ligands were determined. In each complex, the metal center was in a square planar conformation, as expected for Rh(I) and Ir(I) complexes. The five- and six-membered metallocycles formed on complexation of the metal with the ligands were all planar, and the aromaticity of the ligands was maintained. The Rh(I) complex with the tridentate indolyl ligand (L) reacted at room temperature with CH2Cl2 to form the Rh(III) chloromethyl complex [Rh(L)(CO)(CH2Cl)(Cl)] via oxidative addition of the C−Cl bond of CH2Cl2. The Rh/Ir(I) indolyl−imine complexes are efficient catalysts for the intramolecular cyclization of 4-pentynoic acid to form γ-methylene-γ-butyrolactone. A dinuclear Rh(I) complex was the most active catalyst, demonstrating a significant degree of bimetallic cooperativity.